Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/lrg/voltage-2.6
[linux-2.6.git] / fs / jbd / transaction.c
1 /*
2  * linux/fs/jbd/transaction.c
3  *
4  * Written by Stephen C. Tweedie <sct@redhat.com>, 1998
5  *
6  * Copyright 1998 Red Hat corp --- All Rights Reserved
7  *
8  * This file is part of the Linux kernel and is made available under
9  * the terms of the GNU General Public License, version 2, or at your
10  * option, any later version, incorporated herein by reference.
11  *
12  * Generic filesystem transaction handling code; part of the ext2fs
13  * journaling system.
14  *
15  * This file manages transactions (compound commits managed by the
16  * journaling code) and handles (individual atomic operations by the
17  * filesystem).
18  */
19
20 #include <linux/time.h>
21 #include <linux/fs.h>
22 #include <linux/jbd.h>
23 #include <linux/errno.h>
24 #include <linux/slab.h>
25 #include <linux/timer.h>
26 #include <linux/mm.h>
27 #include <linux/highmem.h>
28 #include <linux/hrtimer.h>
29
30 static void __journal_temp_unlink_buffer(struct journal_head *jh);
31
32 /*
33  * get_transaction: obtain a new transaction_t object.
34  *
35  * Simply allocate and initialise a new transaction.  Create it in
36  * RUNNING state and add it to the current journal (which should not
37  * have an existing running transaction: we only make a new transaction
38  * once we have started to commit the old one).
39  *
40  * Preconditions:
41  *      The journal MUST be locked.  We don't perform atomic mallocs on the
42  *      new transaction and we can't block without protecting against other
43  *      processes trying to touch the journal while it is in transition.
44  *
45  * Called under j_state_lock
46  */
47
48 static transaction_t *
49 get_transaction(journal_t *journal, transaction_t *transaction)
50 {
51         transaction->t_journal = journal;
52         transaction->t_state = T_RUNNING;
53         transaction->t_start_time = ktime_get();
54         transaction->t_tid = journal->j_transaction_sequence++;
55         transaction->t_expires = jiffies + journal->j_commit_interval;
56         spin_lock_init(&transaction->t_handle_lock);
57
58         /* Set up the commit timer for the new transaction. */
59         journal->j_commit_timer.expires = round_jiffies(transaction->t_expires);
60         add_timer(&journal->j_commit_timer);
61
62         J_ASSERT(journal->j_running_transaction == NULL);
63         journal->j_running_transaction = transaction;
64
65         return transaction;
66 }
67
68 /*
69  * Handle management.
70  *
71  * A handle_t is an object which represents a single atomic update to a
72  * filesystem, and which tracks all of the modifications which form part
73  * of that one update.
74  */
75
76 /*
77  * start_this_handle: Given a handle, deal with any locking or stalling
78  * needed to make sure that there is enough journal space for the handle
79  * to begin.  Attach the handle to a transaction and set up the
80  * transaction's buffer credits.
81  */
82
83 static int start_this_handle(journal_t *journal, handle_t *handle)
84 {
85         transaction_t *transaction;
86         int needed;
87         int nblocks = handle->h_buffer_credits;
88         transaction_t *new_transaction = NULL;
89         int ret = 0;
90
91         if (nblocks > journal->j_max_transaction_buffers) {
92                 printk(KERN_ERR "JBD: %s wants too many credits (%d > %d)\n",
93                        current->comm, nblocks,
94                        journal->j_max_transaction_buffers);
95                 ret = -ENOSPC;
96                 goto out;
97         }
98
99 alloc_transaction:
100         if (!journal->j_running_transaction) {
101                 new_transaction = kzalloc(sizeof(*new_transaction),
102                                                 GFP_NOFS|__GFP_NOFAIL);
103                 if (!new_transaction) {
104                         ret = -ENOMEM;
105                         goto out;
106                 }
107         }
108
109         jbd_debug(3, "New handle %p going live.\n", handle);
110
111 repeat:
112
113         /*
114          * We need to hold j_state_lock until t_updates has been incremented,
115          * for proper journal barrier handling
116          */
117         spin_lock(&journal->j_state_lock);
118 repeat_locked:
119         if (is_journal_aborted(journal) ||
120             (journal->j_errno != 0 && !(journal->j_flags & JFS_ACK_ERR))) {
121                 spin_unlock(&journal->j_state_lock);
122                 ret = -EROFS;
123                 goto out;
124         }
125
126         /* Wait on the journal's transaction barrier if necessary */
127         if (journal->j_barrier_count) {
128                 spin_unlock(&journal->j_state_lock);
129                 wait_event(journal->j_wait_transaction_locked,
130                                 journal->j_barrier_count == 0);
131                 goto repeat;
132         }
133
134         if (!journal->j_running_transaction) {
135                 if (!new_transaction) {
136                         spin_unlock(&journal->j_state_lock);
137                         goto alloc_transaction;
138                 }
139                 get_transaction(journal, new_transaction);
140                 new_transaction = NULL;
141         }
142
143         transaction = journal->j_running_transaction;
144
145         /*
146          * If the current transaction is locked down for commit, wait for the
147          * lock to be released.
148          */
149         if (transaction->t_state == T_LOCKED) {
150                 DEFINE_WAIT(wait);
151
152                 prepare_to_wait(&journal->j_wait_transaction_locked,
153                                         &wait, TASK_UNINTERRUPTIBLE);
154                 spin_unlock(&journal->j_state_lock);
155                 schedule();
156                 finish_wait(&journal->j_wait_transaction_locked, &wait);
157                 goto repeat;
158         }
159
160         /*
161          * If there is not enough space left in the log to write all potential
162          * buffers requested by this operation, we need to stall pending a log
163          * checkpoint to free some more log space.
164          */
165         spin_lock(&transaction->t_handle_lock);
166         needed = transaction->t_outstanding_credits + nblocks;
167
168         if (needed > journal->j_max_transaction_buffers) {
169                 /*
170                  * If the current transaction is already too large, then start
171                  * to commit it: we can then go back and attach this handle to
172                  * a new transaction.
173                  */
174                 DEFINE_WAIT(wait);
175
176                 jbd_debug(2, "Handle %p starting new commit...\n", handle);
177                 spin_unlock(&transaction->t_handle_lock);
178                 prepare_to_wait(&journal->j_wait_transaction_locked, &wait,
179                                 TASK_UNINTERRUPTIBLE);
180                 __log_start_commit(journal, transaction->t_tid);
181                 spin_unlock(&journal->j_state_lock);
182                 schedule();
183                 finish_wait(&journal->j_wait_transaction_locked, &wait);
184                 goto repeat;
185         }
186
187         /*
188          * The commit code assumes that it can get enough log space
189          * without forcing a checkpoint.  This is *critical* for
190          * correctness: a checkpoint of a buffer which is also
191          * associated with a committing transaction creates a deadlock,
192          * so commit simply cannot force through checkpoints.
193          *
194          * We must therefore ensure the necessary space in the journal
195          * *before* starting to dirty potentially checkpointed buffers
196          * in the new transaction.
197          *
198          * The worst part is, any transaction currently committing can
199          * reduce the free space arbitrarily.  Be careful to account for
200          * those buffers when checkpointing.
201          */
202
203         /*
204          * @@@ AKPM: This seems rather over-defensive.  We're giving commit
205          * a _lot_ of headroom: 1/4 of the journal plus the size of
206          * the committing transaction.  Really, we only need to give it
207          * committing_transaction->t_outstanding_credits plus "enough" for
208          * the log control blocks.
209          * Also, this test is inconsitent with the matching one in
210          * journal_extend().
211          */
212         if (__log_space_left(journal) < jbd_space_needed(journal)) {
213                 jbd_debug(2, "Handle %p waiting for checkpoint...\n", handle);
214                 spin_unlock(&transaction->t_handle_lock);
215                 __log_wait_for_space(journal);
216                 goto repeat_locked;
217         }
218
219         /* OK, account for the buffers that this operation expects to
220          * use and add the handle to the running transaction. */
221
222         handle->h_transaction = transaction;
223         transaction->t_outstanding_credits += nblocks;
224         transaction->t_updates++;
225         transaction->t_handle_count++;
226         jbd_debug(4, "Handle %p given %d credits (total %d, free %d)\n",
227                   handle, nblocks, transaction->t_outstanding_credits,
228                   __log_space_left(journal));
229         spin_unlock(&transaction->t_handle_lock);
230         spin_unlock(&journal->j_state_lock);
231 out:
232         if (unlikely(new_transaction))          /* It's usually NULL */
233                 kfree(new_transaction);
234         return ret;
235 }
236
237 static struct lock_class_key jbd_handle_key;
238
239 /* Allocate a new handle.  This should probably be in a slab... */
240 static handle_t *new_handle(int nblocks)
241 {
242         handle_t *handle = jbd_alloc_handle(GFP_NOFS);
243         if (!handle)
244                 return NULL;
245         memset(handle, 0, sizeof(*handle));
246         handle->h_buffer_credits = nblocks;
247         handle->h_ref = 1;
248
249         lockdep_init_map(&handle->h_lockdep_map, "jbd_handle", &jbd_handle_key, 0);
250
251         return handle;
252 }
253
254 /**
255  * handle_t *journal_start() - Obtain a new handle.
256  * @journal: Journal to start transaction on.
257  * @nblocks: number of block buffer we might modify
258  *
259  * We make sure that the transaction can guarantee at least nblocks of
260  * modified buffers in the log.  We block until the log can guarantee
261  * that much space.
262  *
263  * This function is visible to journal users (like ext3fs), so is not
264  * called with the journal already locked.
265  *
266  * Return a pointer to a newly allocated handle, or NULL on failure
267  */
268 handle_t *journal_start(journal_t *journal, int nblocks)
269 {
270         handle_t *handle = journal_current_handle();
271         int err;
272
273         if (!journal)
274                 return ERR_PTR(-EROFS);
275
276         if (handle) {
277                 J_ASSERT(handle->h_transaction->t_journal == journal);
278                 handle->h_ref++;
279                 return handle;
280         }
281
282         handle = new_handle(nblocks);
283         if (!handle)
284                 return ERR_PTR(-ENOMEM);
285
286         current->journal_info = handle;
287
288         err = start_this_handle(journal, handle);
289         if (err < 0) {
290                 jbd_free_handle(handle);
291                 current->journal_info = NULL;
292                 handle = ERR_PTR(err);
293                 goto out;
294         }
295
296         lock_map_acquire(&handle->h_lockdep_map);
297
298 out:
299         return handle;
300 }
301
302 /**
303  * int journal_extend() - extend buffer credits.
304  * @handle:  handle to 'extend'
305  * @nblocks: nr blocks to try to extend by.
306  *
307  * Some transactions, such as large extends and truncates, can be done
308  * atomically all at once or in several stages.  The operation requests
309  * a credit for a number of buffer modications in advance, but can
310  * extend its credit if it needs more.
311  *
312  * journal_extend tries to give the running handle more buffer credits.
313  * It does not guarantee that allocation - this is a best-effort only.
314  * The calling process MUST be able to deal cleanly with a failure to
315  * extend here.
316  *
317  * Return 0 on success, non-zero on failure.
318  *
319  * return code < 0 implies an error
320  * return code > 0 implies normal transaction-full status.
321  */
322 int journal_extend(handle_t *handle, int nblocks)
323 {
324         transaction_t *transaction = handle->h_transaction;
325         journal_t *journal = transaction->t_journal;
326         int result;
327         int wanted;
328
329         result = -EIO;
330         if (is_handle_aborted(handle))
331                 goto out;
332
333         result = 1;
334
335         spin_lock(&journal->j_state_lock);
336
337         /* Don't extend a locked-down transaction! */
338         if (handle->h_transaction->t_state != T_RUNNING) {
339                 jbd_debug(3, "denied handle %p %d blocks: "
340                           "transaction not running\n", handle, nblocks);
341                 goto error_out;
342         }
343
344         spin_lock(&transaction->t_handle_lock);
345         wanted = transaction->t_outstanding_credits + nblocks;
346
347         if (wanted > journal->j_max_transaction_buffers) {
348                 jbd_debug(3, "denied handle %p %d blocks: "
349                           "transaction too large\n", handle, nblocks);
350                 goto unlock;
351         }
352
353         if (wanted > __log_space_left(journal)) {
354                 jbd_debug(3, "denied handle %p %d blocks: "
355                           "insufficient log space\n", handle, nblocks);
356                 goto unlock;
357         }
358
359         handle->h_buffer_credits += nblocks;
360         transaction->t_outstanding_credits += nblocks;
361         result = 0;
362
363         jbd_debug(3, "extended handle %p by %d\n", handle, nblocks);
364 unlock:
365         spin_unlock(&transaction->t_handle_lock);
366 error_out:
367         spin_unlock(&journal->j_state_lock);
368 out:
369         return result;
370 }
371
372
373 /**
374  * int journal_restart() - restart a handle.
375  * @handle:  handle to restart
376  * @nblocks: nr credits requested
377  *
378  * Restart a handle for a multi-transaction filesystem
379  * operation.
380  *
381  * If the journal_extend() call above fails to grant new buffer credits
382  * to a running handle, a call to journal_restart will commit the
383  * handle's transaction so far and reattach the handle to a new
384  * transaction capabable of guaranteeing the requested number of
385  * credits.
386  */
387
388 int journal_restart(handle_t *handle, int nblocks)
389 {
390         transaction_t *transaction = handle->h_transaction;
391         journal_t *journal = transaction->t_journal;
392         int ret;
393
394         /* If we've had an abort of any type, don't even think about
395          * actually doing the restart! */
396         if (is_handle_aborted(handle))
397                 return 0;
398
399         /*
400          * First unlink the handle from its current transaction, and start the
401          * commit on that.
402          */
403         J_ASSERT(transaction->t_updates > 0);
404         J_ASSERT(journal_current_handle() == handle);
405
406         spin_lock(&journal->j_state_lock);
407         spin_lock(&transaction->t_handle_lock);
408         transaction->t_outstanding_credits -= handle->h_buffer_credits;
409         transaction->t_updates--;
410
411         if (!transaction->t_updates)
412                 wake_up(&journal->j_wait_updates);
413         spin_unlock(&transaction->t_handle_lock);
414
415         jbd_debug(2, "restarting handle %p\n", handle);
416         __log_start_commit(journal, transaction->t_tid);
417         spin_unlock(&journal->j_state_lock);
418
419         handle->h_buffer_credits = nblocks;
420         ret = start_this_handle(journal, handle);
421         return ret;
422 }
423
424
425 /**
426  * void journal_lock_updates () - establish a transaction barrier.
427  * @journal:  Journal to establish a barrier on.
428  *
429  * This locks out any further updates from being started, and blocks
430  * until all existing updates have completed, returning only once the
431  * journal is in a quiescent state with no updates running.
432  *
433  * The journal lock should not be held on entry.
434  */
435 void journal_lock_updates(journal_t *journal)
436 {
437         DEFINE_WAIT(wait);
438
439         spin_lock(&journal->j_state_lock);
440         ++journal->j_barrier_count;
441
442         /* Wait until there are no running updates */
443         while (1) {
444                 transaction_t *transaction = journal->j_running_transaction;
445
446                 if (!transaction)
447                         break;
448
449                 spin_lock(&transaction->t_handle_lock);
450                 if (!transaction->t_updates) {
451                         spin_unlock(&transaction->t_handle_lock);
452                         break;
453                 }
454                 prepare_to_wait(&journal->j_wait_updates, &wait,
455                                 TASK_UNINTERRUPTIBLE);
456                 spin_unlock(&transaction->t_handle_lock);
457                 spin_unlock(&journal->j_state_lock);
458                 schedule();
459                 finish_wait(&journal->j_wait_updates, &wait);
460                 spin_lock(&journal->j_state_lock);
461         }
462         spin_unlock(&journal->j_state_lock);
463
464         /*
465          * We have now established a barrier against other normal updates, but
466          * we also need to barrier against other journal_lock_updates() calls
467          * to make sure that we serialise special journal-locked operations
468          * too.
469          */
470         mutex_lock(&journal->j_barrier);
471 }
472
473 /**
474  * void journal_unlock_updates (journal_t* journal) - release barrier
475  * @journal:  Journal to release the barrier on.
476  *
477  * Release a transaction barrier obtained with journal_lock_updates().
478  *
479  * Should be called without the journal lock held.
480  */
481 void journal_unlock_updates (journal_t *journal)
482 {
483         J_ASSERT(journal->j_barrier_count != 0);
484
485         mutex_unlock(&journal->j_barrier);
486         spin_lock(&journal->j_state_lock);
487         --journal->j_barrier_count;
488         spin_unlock(&journal->j_state_lock);
489         wake_up(&journal->j_wait_transaction_locked);
490 }
491
492 /*
493  * Report any unexpected dirty buffers which turn up.  Normally those
494  * indicate an error, but they can occur if the user is running (say)
495  * tune2fs to modify the live filesystem, so we need the option of
496  * continuing as gracefully as possible.  #
497  *
498  * The caller should already hold the journal lock and
499  * j_list_lock spinlock: most callers will need those anyway
500  * in order to probe the buffer's journaling state safely.
501  */
502 static void jbd_unexpected_dirty_buffer(struct journal_head *jh)
503 {
504         int jlist;
505
506         /* If this buffer is one which might reasonably be dirty
507          * --- ie. data, or not part of this journal --- then
508          * we're OK to leave it alone, but otherwise we need to
509          * move the dirty bit to the journal's own internal
510          * JBDDirty bit. */
511         jlist = jh->b_jlist;
512
513         if (jlist == BJ_Metadata || jlist == BJ_Reserved ||
514             jlist == BJ_Shadow || jlist == BJ_Forget) {
515                 struct buffer_head *bh = jh2bh(jh);
516
517                 if (test_clear_buffer_dirty(bh))
518                         set_buffer_jbddirty(bh);
519         }
520 }
521
522 /*
523  * If the buffer is already part of the current transaction, then there
524  * is nothing we need to do.  If it is already part of a prior
525  * transaction which we are still committing to disk, then we need to
526  * make sure that we do not overwrite the old copy: we do copy-out to
527  * preserve the copy going to disk.  We also account the buffer against
528  * the handle's metadata buffer credits (unless the buffer is already
529  * part of the transaction, that is).
530  *
531  */
532 static int
533 do_get_write_access(handle_t *handle, struct journal_head *jh,
534                         int force_copy)
535 {
536         struct buffer_head *bh;
537         transaction_t *transaction;
538         journal_t *journal;
539         int error;
540         char *frozen_buffer = NULL;
541         int need_copy = 0;
542
543         if (is_handle_aborted(handle))
544                 return -EROFS;
545
546         transaction = handle->h_transaction;
547         journal = transaction->t_journal;
548
549         jbd_debug(5, "buffer_head %p, force_copy %d\n", jh, force_copy);
550
551         JBUFFER_TRACE(jh, "entry");
552 repeat:
553         bh = jh2bh(jh);
554
555         /* @@@ Need to check for errors here at some point. */
556
557         lock_buffer(bh);
558         jbd_lock_bh_state(bh);
559
560         /* We now hold the buffer lock so it is safe to query the buffer
561          * state.  Is the buffer dirty?
562          *
563          * If so, there are two possibilities.  The buffer may be
564          * non-journaled, and undergoing a quite legitimate writeback.
565          * Otherwise, it is journaled, and we don't expect dirty buffers
566          * in that state (the buffers should be marked JBD_Dirty
567          * instead.)  So either the IO is being done under our own
568          * control and this is a bug, or it's a third party IO such as
569          * dump(8) (which may leave the buffer scheduled for read ---
570          * ie. locked but not dirty) or tune2fs (which may actually have
571          * the buffer dirtied, ugh.)  */
572
573         if (buffer_dirty(bh)) {
574                 /*
575                  * First question: is this buffer already part of the current
576                  * transaction or the existing committing transaction?
577                  */
578                 if (jh->b_transaction) {
579                         J_ASSERT_JH(jh,
580                                 jh->b_transaction == transaction ||
581                                 jh->b_transaction ==
582                                         journal->j_committing_transaction);
583                         if (jh->b_next_transaction)
584                                 J_ASSERT_JH(jh, jh->b_next_transaction ==
585                                                         transaction);
586                 }
587                 /*
588                  * In any case we need to clean the dirty flag and we must
589                  * do it under the buffer lock to be sure we don't race
590                  * with running write-out.
591                  */
592                 JBUFFER_TRACE(jh, "Unexpected dirty buffer");
593                 jbd_unexpected_dirty_buffer(jh);
594         }
595
596         unlock_buffer(bh);
597
598         error = -EROFS;
599         if (is_handle_aborted(handle)) {
600                 jbd_unlock_bh_state(bh);
601                 goto out;
602         }
603         error = 0;
604
605         /*
606          * The buffer is already part of this transaction if b_transaction or
607          * b_next_transaction points to it
608          */
609         if (jh->b_transaction == transaction ||
610             jh->b_next_transaction == transaction)
611                 goto done;
612
613         /*
614          * this is the first time this transaction is touching this buffer,
615          * reset the modified flag
616          */
617         jh->b_modified = 0;
618
619         /*
620          * If there is already a copy-out version of this buffer, then we don't
621          * need to make another one
622          */
623         if (jh->b_frozen_data) {
624                 JBUFFER_TRACE(jh, "has frozen data");
625                 J_ASSERT_JH(jh, jh->b_next_transaction == NULL);
626                 jh->b_next_transaction = transaction;
627                 goto done;
628         }
629
630         /* Is there data here we need to preserve? */
631
632         if (jh->b_transaction && jh->b_transaction != transaction) {
633                 JBUFFER_TRACE(jh, "owned by older transaction");
634                 J_ASSERT_JH(jh, jh->b_next_transaction == NULL);
635                 J_ASSERT_JH(jh, jh->b_transaction ==
636                                         journal->j_committing_transaction);
637
638                 /* There is one case we have to be very careful about.
639                  * If the committing transaction is currently writing
640                  * this buffer out to disk and has NOT made a copy-out,
641                  * then we cannot modify the buffer contents at all
642                  * right now.  The essence of copy-out is that it is the
643                  * extra copy, not the primary copy, which gets
644                  * journaled.  If the primary copy is already going to
645                  * disk then we cannot do copy-out here. */
646
647                 if (jh->b_jlist == BJ_Shadow) {
648                         DEFINE_WAIT_BIT(wait, &bh->b_state, BH_Unshadow);
649                         wait_queue_head_t *wqh;
650
651                         wqh = bit_waitqueue(&bh->b_state, BH_Unshadow);
652
653                         JBUFFER_TRACE(jh, "on shadow: sleep");
654                         jbd_unlock_bh_state(bh);
655                         /* commit wakes up all shadow buffers after IO */
656                         for ( ; ; ) {
657                                 prepare_to_wait(wqh, &wait.wait,
658                                                 TASK_UNINTERRUPTIBLE);
659                                 if (jh->b_jlist != BJ_Shadow)
660                                         break;
661                                 schedule();
662                         }
663                         finish_wait(wqh, &wait.wait);
664                         goto repeat;
665                 }
666
667                 /* Only do the copy if the currently-owning transaction
668                  * still needs it.  If it is on the Forget list, the
669                  * committing transaction is past that stage.  The
670                  * buffer had better remain locked during the kmalloc,
671                  * but that should be true --- we hold the journal lock
672                  * still and the buffer is already on the BUF_JOURNAL
673                  * list so won't be flushed.
674                  *
675                  * Subtle point, though: if this is a get_undo_access,
676                  * then we will be relying on the frozen_data to contain
677                  * the new value of the committed_data record after the
678                  * transaction, so we HAVE to force the frozen_data copy
679                  * in that case. */
680
681                 if (jh->b_jlist != BJ_Forget || force_copy) {
682                         JBUFFER_TRACE(jh, "generate frozen data");
683                         if (!frozen_buffer) {
684                                 JBUFFER_TRACE(jh, "allocate memory for buffer");
685                                 jbd_unlock_bh_state(bh);
686                                 frozen_buffer =
687                                         jbd_alloc(jh2bh(jh)->b_size,
688                                                          GFP_NOFS);
689                                 if (!frozen_buffer) {
690                                         printk(KERN_EMERG
691                                                "%s: OOM for frozen_buffer\n",
692                                                __func__);
693                                         JBUFFER_TRACE(jh, "oom!");
694                                         error = -ENOMEM;
695                                         jbd_lock_bh_state(bh);
696                                         goto done;
697                                 }
698                                 goto repeat;
699                         }
700                         jh->b_frozen_data = frozen_buffer;
701                         frozen_buffer = NULL;
702                         need_copy = 1;
703                 }
704                 jh->b_next_transaction = transaction;
705         }
706
707
708         /*
709          * Finally, if the buffer is not journaled right now, we need to make
710          * sure it doesn't get written to disk before the caller actually
711          * commits the new data
712          */
713         if (!jh->b_transaction) {
714                 JBUFFER_TRACE(jh, "no transaction");
715                 J_ASSERT_JH(jh, !jh->b_next_transaction);
716                 jh->b_transaction = transaction;
717                 JBUFFER_TRACE(jh, "file as BJ_Reserved");
718                 spin_lock(&journal->j_list_lock);
719                 __journal_file_buffer(jh, transaction, BJ_Reserved);
720                 spin_unlock(&journal->j_list_lock);
721         }
722
723 done:
724         if (need_copy) {
725                 struct page *page;
726                 int offset;
727                 char *source;
728
729                 J_EXPECT_JH(jh, buffer_uptodate(jh2bh(jh)),
730                             "Possible IO failure.\n");
731                 page = jh2bh(jh)->b_page;
732                 offset = ((unsigned long) jh2bh(jh)->b_data) & ~PAGE_MASK;
733                 source = kmap_atomic(page, KM_USER0);
734                 memcpy(jh->b_frozen_data, source+offset, jh2bh(jh)->b_size);
735                 kunmap_atomic(source, KM_USER0);
736         }
737         jbd_unlock_bh_state(bh);
738
739         /*
740          * If we are about to journal a buffer, then any revoke pending on it is
741          * no longer valid
742          */
743         journal_cancel_revoke(handle, jh);
744
745 out:
746         if (unlikely(frozen_buffer))    /* It's usually NULL */
747                 jbd_free(frozen_buffer, bh->b_size);
748
749         JBUFFER_TRACE(jh, "exit");
750         return error;
751 }
752
753 /**
754  * int journal_get_write_access() - notify intent to modify a buffer for metadata (not data) update.
755  * @handle: transaction to add buffer modifications to
756  * @bh:     bh to be used for metadata writes
757  *
758  * Returns an error code or 0 on success.
759  *
760  * In full data journalling mode the buffer may be of type BJ_AsyncData,
761  * because we're write()ing a buffer which is also part of a shared mapping.
762  */
763
764 int journal_get_write_access(handle_t *handle, struct buffer_head *bh)
765 {
766         struct journal_head *jh = journal_add_journal_head(bh);
767         int rc;
768
769         /* We do not want to get caught playing with fields which the
770          * log thread also manipulates.  Make sure that the buffer
771          * completes any outstanding IO before proceeding. */
772         rc = do_get_write_access(handle, jh, 0);
773         journal_put_journal_head(jh);
774         return rc;
775 }
776
777
778 /*
779  * When the user wants to journal a newly created buffer_head
780  * (ie. getblk() returned a new buffer and we are going to populate it
781  * manually rather than reading off disk), then we need to keep the
782  * buffer_head locked until it has been completely filled with new
783  * data.  In this case, we should be able to make the assertion that
784  * the bh is not already part of an existing transaction.
785  *
786  * The buffer should already be locked by the caller by this point.
787  * There is no lock ranking violation: it was a newly created,
788  * unlocked buffer beforehand. */
789
790 /**
791  * int journal_get_create_access () - notify intent to use newly created bh
792  * @handle: transaction to new buffer to
793  * @bh: new buffer.
794  *
795  * Call this if you create a new bh.
796  */
797 int journal_get_create_access(handle_t *handle, struct buffer_head *bh)
798 {
799         transaction_t *transaction = handle->h_transaction;
800         journal_t *journal = transaction->t_journal;
801         struct journal_head *jh = journal_add_journal_head(bh);
802         int err;
803
804         jbd_debug(5, "journal_head %p\n", jh);
805         err = -EROFS;
806         if (is_handle_aborted(handle))
807                 goto out;
808         err = 0;
809
810         JBUFFER_TRACE(jh, "entry");
811         /*
812          * The buffer may already belong to this transaction due to pre-zeroing
813          * in the filesystem's new_block code.  It may also be on the previous,
814          * committing transaction's lists, but it HAS to be in Forget state in
815          * that case: the transaction must have deleted the buffer for it to be
816          * reused here.
817          */
818         jbd_lock_bh_state(bh);
819         spin_lock(&journal->j_list_lock);
820         J_ASSERT_JH(jh, (jh->b_transaction == transaction ||
821                 jh->b_transaction == NULL ||
822                 (jh->b_transaction == journal->j_committing_transaction &&
823                           jh->b_jlist == BJ_Forget)));
824
825         J_ASSERT_JH(jh, jh->b_next_transaction == NULL);
826         J_ASSERT_JH(jh, buffer_locked(jh2bh(jh)));
827
828         if (jh->b_transaction == NULL) {
829                 jh->b_transaction = transaction;
830
831                 /* first access by this transaction */
832                 jh->b_modified = 0;
833
834                 JBUFFER_TRACE(jh, "file as BJ_Reserved");
835                 __journal_file_buffer(jh, transaction, BJ_Reserved);
836         } else if (jh->b_transaction == journal->j_committing_transaction) {
837                 /* first access by this transaction */
838                 jh->b_modified = 0;
839
840                 JBUFFER_TRACE(jh, "set next transaction");
841                 jh->b_next_transaction = transaction;
842         }
843         spin_unlock(&journal->j_list_lock);
844         jbd_unlock_bh_state(bh);
845
846         /*
847          * akpm: I added this.  ext3_alloc_branch can pick up new indirect
848          * blocks which contain freed but then revoked metadata.  We need
849          * to cancel the revoke in case we end up freeing it yet again
850          * and the reallocating as data - this would cause a second revoke,
851          * which hits an assertion error.
852          */
853         JBUFFER_TRACE(jh, "cancelling revoke");
854         journal_cancel_revoke(handle, jh);
855         journal_put_journal_head(jh);
856 out:
857         return err;
858 }
859
860 /**
861  * int journal_get_undo_access() - Notify intent to modify metadata with non-rewindable consequences
862  * @handle: transaction
863  * @bh: buffer to undo
864  *
865  * Sometimes there is a need to distinguish between metadata which has
866  * been committed to disk and that which has not.  The ext3fs code uses
867  * this for freeing and allocating space, we have to make sure that we
868  * do not reuse freed space until the deallocation has been committed,
869  * since if we overwrote that space we would make the delete
870  * un-rewindable in case of a crash.
871  *
872  * To deal with that, journal_get_undo_access requests write access to a
873  * buffer for parts of non-rewindable operations such as delete
874  * operations on the bitmaps.  The journaling code must keep a copy of
875  * the buffer's contents prior to the undo_access call until such time
876  * as we know that the buffer has definitely been committed to disk.
877  *
878  * We never need to know which transaction the committed data is part
879  * of, buffers touched here are guaranteed to be dirtied later and so
880  * will be committed to a new transaction in due course, at which point
881  * we can discard the old committed data pointer.
882  *
883  * Returns error number or 0 on success.
884  */
885 int journal_get_undo_access(handle_t *handle, struct buffer_head *bh)
886 {
887         int err;
888         struct journal_head *jh = journal_add_journal_head(bh);
889         char *committed_data = NULL;
890
891         JBUFFER_TRACE(jh, "entry");
892
893         /*
894          * Do this first --- it can drop the journal lock, so we want to
895          * make sure that obtaining the committed_data is done
896          * atomically wrt. completion of any outstanding commits.
897          */
898         err = do_get_write_access(handle, jh, 1);
899         if (err)
900                 goto out;
901
902 repeat:
903         if (!jh->b_committed_data) {
904                 committed_data = jbd_alloc(jh2bh(jh)->b_size, GFP_NOFS);
905                 if (!committed_data) {
906                         printk(KERN_EMERG "%s: No memory for committed data\n",
907                                 __func__);
908                         err = -ENOMEM;
909                         goto out;
910                 }
911         }
912
913         jbd_lock_bh_state(bh);
914         if (!jh->b_committed_data) {
915                 /* Copy out the current buffer contents into the
916                  * preserved, committed copy. */
917                 JBUFFER_TRACE(jh, "generate b_committed data");
918                 if (!committed_data) {
919                         jbd_unlock_bh_state(bh);
920                         goto repeat;
921                 }
922
923                 jh->b_committed_data = committed_data;
924                 committed_data = NULL;
925                 memcpy(jh->b_committed_data, bh->b_data, bh->b_size);
926         }
927         jbd_unlock_bh_state(bh);
928 out:
929         journal_put_journal_head(jh);
930         if (unlikely(committed_data))
931                 jbd_free(committed_data, bh->b_size);
932         return err;
933 }
934
935 /**
936  * int journal_dirty_data() - mark a buffer as containing dirty data to be flushed
937  * @handle: transaction
938  * @bh: bufferhead to mark
939  *
940  * Description:
941  * Mark a buffer as containing dirty data which needs to be flushed before
942  * we can commit the current transaction.
943  *
944  * The buffer is placed on the transaction's data list and is marked as
945  * belonging to the transaction.
946  *
947  * Returns error number or 0 on success.
948  *
949  * journal_dirty_data() can be called via page_launder->ext3_writepage
950  * by kswapd.
951  */
952 int journal_dirty_data(handle_t *handle, struct buffer_head *bh)
953 {
954         journal_t *journal = handle->h_transaction->t_journal;
955         int need_brelse = 0;
956         struct journal_head *jh;
957         int ret = 0;
958
959         if (is_handle_aborted(handle))
960                 return ret;
961
962         jh = journal_add_journal_head(bh);
963         JBUFFER_TRACE(jh, "entry");
964
965         /*
966          * The buffer could *already* be dirty.  Writeout can start
967          * at any time.
968          */
969         jbd_debug(4, "jh: %p, tid:%d\n", jh, handle->h_transaction->t_tid);
970
971         /*
972          * What if the buffer is already part of a running transaction?
973          *
974          * There are two cases:
975          * 1) It is part of the current running transaction.  Refile it,
976          *    just in case we have allocated it as metadata, deallocated
977          *    it, then reallocated it as data.
978          * 2) It is part of the previous, still-committing transaction.
979          *    If all we want to do is to guarantee that the buffer will be
980          *    written to disk before this new transaction commits, then
981          *    being sure that the *previous* transaction has this same
982          *    property is sufficient for us!  Just leave it on its old
983          *    transaction.
984          *
985          * In case (2), the buffer must not already exist as metadata
986          * --- that would violate write ordering (a transaction is free
987          * to write its data at any point, even before the previous
988          * committing transaction has committed).  The caller must
989          * never, ever allow this to happen: there's nothing we can do
990          * about it in this layer.
991          */
992         jbd_lock_bh_state(bh);
993         spin_lock(&journal->j_list_lock);
994
995         /* Now that we have bh_state locked, are we really still mapped? */
996         if (!buffer_mapped(bh)) {
997                 JBUFFER_TRACE(jh, "unmapped buffer, bailing out");
998                 goto no_journal;
999         }
1000
1001         if (jh->b_transaction) {
1002                 JBUFFER_TRACE(jh, "has transaction");
1003                 if (jh->b_transaction != handle->h_transaction) {
1004                         JBUFFER_TRACE(jh, "belongs to older transaction");
1005                         J_ASSERT_JH(jh, jh->b_transaction ==
1006                                         journal->j_committing_transaction);
1007
1008                         /* @@@ IS THIS TRUE  ? */
1009                         /*
1010                          * Not any more.  Scenario: someone does a write()
1011                          * in data=journal mode.  The buffer's transaction has
1012                          * moved into commit.  Then someone does another
1013                          * write() to the file.  We do the frozen data copyout
1014                          * and set b_next_transaction to point to j_running_t.
1015                          * And while we're in that state, someone does a
1016                          * writepage() in an attempt to pageout the same area
1017                          * of the file via a shared mapping.  At present that
1018                          * calls journal_dirty_data(), and we get right here.
1019                          * It may be too late to journal the data.  Simply
1020                          * falling through to the next test will suffice: the
1021                          * data will be dirty and wil be checkpointed.  The
1022                          * ordering comments in the next comment block still
1023                          * apply.
1024                          */
1025                         //J_ASSERT_JH(jh, jh->b_next_transaction == NULL);
1026
1027                         /*
1028                          * If we're journalling data, and this buffer was
1029                          * subject to a write(), it could be metadata, forget
1030                          * or shadow against the committing transaction.  Now,
1031                          * someone has dirtied the same darn page via a mapping
1032                          * and it is being writepage()'d.
1033                          * We *could* just steal the page from commit, with some
1034                          * fancy locking there.  Instead, we just skip it -
1035                          * don't tie the page's buffers to the new transaction
1036                          * at all.
1037                          * Implication: if we crash before the writepage() data
1038                          * is written into the filesystem, recovery will replay
1039                          * the write() data.
1040                          */
1041                         if (jh->b_jlist != BJ_None &&
1042                                         jh->b_jlist != BJ_SyncData &&
1043                                         jh->b_jlist != BJ_Locked) {
1044                                 JBUFFER_TRACE(jh, "Not stealing");
1045                                 goto no_journal;
1046                         }
1047
1048                         /*
1049                          * This buffer may be undergoing writeout in commit.  We
1050                          * can't return from here and let the caller dirty it
1051                          * again because that can cause the write-out loop in
1052                          * commit to never terminate.
1053                          */
1054                         if (buffer_dirty(bh)) {
1055                                 get_bh(bh);
1056                                 spin_unlock(&journal->j_list_lock);
1057                                 jbd_unlock_bh_state(bh);
1058                                 need_brelse = 1;
1059                                 sync_dirty_buffer(bh);
1060                                 jbd_lock_bh_state(bh);
1061                                 spin_lock(&journal->j_list_lock);
1062                                 /* Since we dropped the lock... */
1063                                 if (!buffer_mapped(bh)) {
1064                                         JBUFFER_TRACE(jh, "buffer got unmapped");
1065                                         goto no_journal;
1066                                 }
1067                                 /* The buffer may become locked again at any
1068                                    time if it is redirtied */
1069                         }
1070
1071                         /*
1072                          * We cannot remove the buffer with io error from the
1073                          * committing transaction, because otherwise it would
1074                          * miss the error and the commit would not abort.
1075                          */
1076                         if (unlikely(!buffer_uptodate(bh))) {
1077                                 ret = -EIO;
1078                                 goto no_journal;
1079                         }
1080
1081                         if (jh->b_transaction != NULL) {
1082                                 JBUFFER_TRACE(jh, "unfile from commit");
1083                                 __journal_temp_unlink_buffer(jh);
1084                                 /* It still points to the committing
1085                                  * transaction; move it to this one so
1086                                  * that the refile assert checks are
1087                                  * happy. */
1088                                 jh->b_transaction = handle->h_transaction;
1089                         }
1090                         /* The buffer will be refiled below */
1091
1092                 }
1093                 /*
1094                  * Special case --- the buffer might actually have been
1095                  * allocated and then immediately deallocated in the previous,
1096                  * committing transaction, so might still be left on that
1097                  * transaction's metadata lists.
1098                  */
1099                 if (jh->b_jlist != BJ_SyncData && jh->b_jlist != BJ_Locked) {
1100                         JBUFFER_TRACE(jh, "not on correct data list: unfile");
1101                         J_ASSERT_JH(jh, jh->b_jlist != BJ_Shadow);
1102                         __journal_temp_unlink_buffer(jh);
1103                         jh->b_transaction = handle->h_transaction;
1104                         JBUFFER_TRACE(jh, "file as data");
1105                         __journal_file_buffer(jh, handle->h_transaction,
1106                                                 BJ_SyncData);
1107                 }
1108         } else {
1109                 JBUFFER_TRACE(jh, "not on a transaction");
1110                 __journal_file_buffer(jh, handle->h_transaction, BJ_SyncData);
1111         }
1112 no_journal:
1113         spin_unlock(&journal->j_list_lock);
1114         jbd_unlock_bh_state(bh);
1115         if (need_brelse) {
1116                 BUFFER_TRACE(bh, "brelse");
1117                 __brelse(bh);
1118         }
1119         JBUFFER_TRACE(jh, "exit");
1120         journal_put_journal_head(jh);
1121         return ret;
1122 }
1123
1124 /**
1125  * int journal_dirty_metadata() - mark a buffer as containing dirty metadata
1126  * @handle: transaction to add buffer to.
1127  * @bh: buffer to mark
1128  *
1129  * Mark dirty metadata which needs to be journaled as part of the current
1130  * transaction.
1131  *
1132  * The buffer is placed on the transaction's metadata list and is marked
1133  * as belonging to the transaction.
1134  *
1135  * Returns error number or 0 on success.
1136  *
1137  * Special care needs to be taken if the buffer already belongs to the
1138  * current committing transaction (in which case we should have frozen
1139  * data present for that commit).  In that case, we don't relink the
1140  * buffer: that only gets done when the old transaction finally
1141  * completes its commit.
1142  */
1143 int journal_dirty_metadata(handle_t *handle, struct buffer_head *bh)
1144 {
1145         transaction_t *transaction = handle->h_transaction;
1146         journal_t *journal = transaction->t_journal;
1147         struct journal_head *jh = bh2jh(bh);
1148
1149         jbd_debug(5, "journal_head %p\n", jh);
1150         JBUFFER_TRACE(jh, "entry");
1151         if (is_handle_aborted(handle))
1152                 goto out;
1153
1154         jbd_lock_bh_state(bh);
1155
1156         if (jh->b_modified == 0) {
1157                 /*
1158                  * This buffer's got modified and becoming part
1159                  * of the transaction. This needs to be done
1160                  * once a transaction -bzzz
1161                  */
1162                 jh->b_modified = 1;
1163                 J_ASSERT_JH(jh, handle->h_buffer_credits > 0);
1164                 handle->h_buffer_credits--;
1165         }
1166
1167         /*
1168          * fastpath, to avoid expensive locking.  If this buffer is already
1169          * on the running transaction's metadata list there is nothing to do.
1170          * Nobody can take it off again because there is a handle open.
1171          * I _think_ we're OK here with SMP barriers - a mistaken decision will
1172          * result in this test being false, so we go in and take the locks.
1173          */
1174         if (jh->b_transaction == transaction && jh->b_jlist == BJ_Metadata) {
1175                 JBUFFER_TRACE(jh, "fastpath");
1176                 J_ASSERT_JH(jh, jh->b_transaction ==
1177                                         journal->j_running_transaction);
1178                 goto out_unlock_bh;
1179         }
1180
1181         set_buffer_jbddirty(bh);
1182
1183         /*
1184          * Metadata already on the current transaction list doesn't
1185          * need to be filed.  Metadata on another transaction's list must
1186          * be committing, and will be refiled once the commit completes:
1187          * leave it alone for now.
1188          */
1189         if (jh->b_transaction != transaction) {
1190                 JBUFFER_TRACE(jh, "already on other transaction");
1191                 J_ASSERT_JH(jh, jh->b_transaction ==
1192                                         journal->j_committing_transaction);
1193                 J_ASSERT_JH(jh, jh->b_next_transaction == transaction);
1194                 /* And this case is illegal: we can't reuse another
1195                  * transaction's data buffer, ever. */
1196                 goto out_unlock_bh;
1197         }
1198
1199         /* That test should have eliminated the following case: */
1200         J_ASSERT_JH(jh, jh->b_frozen_data == NULL);
1201
1202         JBUFFER_TRACE(jh, "file as BJ_Metadata");
1203         spin_lock(&journal->j_list_lock);
1204         __journal_file_buffer(jh, handle->h_transaction, BJ_Metadata);
1205         spin_unlock(&journal->j_list_lock);
1206 out_unlock_bh:
1207         jbd_unlock_bh_state(bh);
1208 out:
1209         JBUFFER_TRACE(jh, "exit");
1210         return 0;
1211 }
1212
1213 /*
1214  * journal_release_buffer: undo a get_write_access without any buffer
1215  * updates, if the update decided in the end that it didn't need access.
1216  *
1217  */
1218 void
1219 journal_release_buffer(handle_t *handle, struct buffer_head *bh)
1220 {
1221         BUFFER_TRACE(bh, "entry");
1222 }
1223
1224 /**
1225  * void journal_forget() - bforget() for potentially-journaled buffers.
1226  * @handle: transaction handle
1227  * @bh:     bh to 'forget'
1228  *
1229  * We can only do the bforget if there are no commits pending against the
1230  * buffer.  If the buffer is dirty in the current running transaction we
1231  * can safely unlink it.
1232  *
1233  * bh may not be a journalled buffer at all - it may be a non-JBD
1234  * buffer which came off the hashtable.  Check for this.
1235  *
1236  * Decrements bh->b_count by one.
1237  *
1238  * Allow this call even if the handle has aborted --- it may be part of
1239  * the caller's cleanup after an abort.
1240  */
1241 int journal_forget (handle_t *handle, struct buffer_head *bh)
1242 {
1243         transaction_t *transaction = handle->h_transaction;
1244         journal_t *journal = transaction->t_journal;
1245         struct journal_head *jh;
1246         int drop_reserve = 0;
1247         int err = 0;
1248         int was_modified = 0;
1249
1250         BUFFER_TRACE(bh, "entry");
1251
1252         jbd_lock_bh_state(bh);
1253         spin_lock(&journal->j_list_lock);
1254
1255         if (!buffer_jbd(bh))
1256                 goto not_jbd;
1257         jh = bh2jh(bh);
1258
1259         /* Critical error: attempting to delete a bitmap buffer, maybe?
1260          * Don't do any jbd operations, and return an error. */
1261         if (!J_EXPECT_JH(jh, !jh->b_committed_data,
1262                          "inconsistent data on disk")) {
1263                 err = -EIO;
1264                 goto not_jbd;
1265         }
1266
1267         /* keep track of wether or not this transaction modified us */
1268         was_modified = jh->b_modified;
1269
1270         /*
1271          * The buffer's going from the transaction, we must drop
1272          * all references -bzzz
1273          */
1274         jh->b_modified = 0;
1275
1276         if (jh->b_transaction == handle->h_transaction) {
1277                 J_ASSERT_JH(jh, !jh->b_frozen_data);
1278
1279                 /* If we are forgetting a buffer which is already part
1280                  * of this transaction, then we can just drop it from
1281                  * the transaction immediately. */
1282                 clear_buffer_dirty(bh);
1283                 clear_buffer_jbddirty(bh);
1284
1285                 JBUFFER_TRACE(jh, "belongs to current transaction: unfile");
1286
1287                 /*
1288                  * we only want to drop a reference if this transaction
1289                  * modified the buffer
1290                  */
1291                 if (was_modified)
1292                         drop_reserve = 1;
1293
1294                 /*
1295                  * We are no longer going to journal this buffer.
1296                  * However, the commit of this transaction is still
1297                  * important to the buffer: the delete that we are now
1298                  * processing might obsolete an old log entry, so by
1299                  * committing, we can satisfy the buffer's checkpoint.
1300                  *
1301                  * So, if we have a checkpoint on the buffer, we should
1302                  * now refile the buffer on our BJ_Forget list so that
1303                  * we know to remove the checkpoint after we commit.
1304                  */
1305
1306                 if (jh->b_cp_transaction) {
1307                         __journal_temp_unlink_buffer(jh);
1308                         __journal_file_buffer(jh, transaction, BJ_Forget);
1309                 } else {
1310                         __journal_unfile_buffer(jh);
1311                         journal_remove_journal_head(bh);
1312                         __brelse(bh);
1313                         if (!buffer_jbd(bh)) {
1314                                 spin_unlock(&journal->j_list_lock);
1315                                 jbd_unlock_bh_state(bh);
1316                                 __bforget(bh);
1317                                 goto drop;
1318                         }
1319                 }
1320         } else if (jh->b_transaction) {
1321                 J_ASSERT_JH(jh, (jh->b_transaction ==
1322                                  journal->j_committing_transaction));
1323                 /* However, if the buffer is still owned by a prior
1324                  * (committing) transaction, we can't drop it yet... */
1325                 JBUFFER_TRACE(jh, "belongs to older transaction");
1326                 /* ... but we CAN drop it from the new transaction if we
1327                  * have also modified it since the original commit. */
1328
1329                 if (jh->b_next_transaction) {
1330                         J_ASSERT(jh->b_next_transaction == transaction);
1331                         jh->b_next_transaction = NULL;
1332
1333                         /*
1334                          * only drop a reference if this transaction modified
1335                          * the buffer
1336                          */
1337                         if (was_modified)
1338                                 drop_reserve = 1;
1339                 }
1340         }
1341
1342 not_jbd:
1343         spin_unlock(&journal->j_list_lock);
1344         jbd_unlock_bh_state(bh);
1345         __brelse(bh);
1346 drop:
1347         if (drop_reserve) {
1348                 /* no need to reserve log space for this block -bzzz */
1349                 handle->h_buffer_credits++;
1350         }
1351         return err;
1352 }
1353
1354 /**
1355  * int journal_stop() - complete a transaction
1356  * @handle: tranaction to complete.
1357  *
1358  * All done for a particular handle.
1359  *
1360  * There is not much action needed here.  We just return any remaining
1361  * buffer credits to the transaction and remove the handle.  The only
1362  * complication is that we need to start a commit operation if the
1363  * filesystem is marked for synchronous update.
1364  *
1365  * journal_stop itself will not usually return an error, but it may
1366  * do so in unusual circumstances.  In particular, expect it to
1367  * return -EIO if a journal_abort has been executed since the
1368  * transaction began.
1369  */
1370 int journal_stop(handle_t *handle)
1371 {
1372         transaction_t *transaction = handle->h_transaction;
1373         journal_t *journal = transaction->t_journal;
1374         int err;
1375         pid_t pid;
1376
1377         J_ASSERT(journal_current_handle() == handle);
1378
1379         if (is_handle_aborted(handle))
1380                 err = -EIO;
1381         else {
1382                 J_ASSERT(transaction->t_updates > 0);
1383                 err = 0;
1384         }
1385
1386         if (--handle->h_ref > 0) {
1387                 jbd_debug(4, "h_ref %d -> %d\n", handle->h_ref + 1,
1388                           handle->h_ref);
1389                 return err;
1390         }
1391
1392         jbd_debug(4, "Handle %p going down\n", handle);
1393
1394         /*
1395          * Implement synchronous transaction batching.  If the handle
1396          * was synchronous, don't force a commit immediately.  Let's
1397          * yield and let another thread piggyback onto this transaction.
1398          * Keep doing that while new threads continue to arrive.
1399          * It doesn't cost much - we're about to run a commit and sleep
1400          * on IO anyway.  Speeds up many-threaded, many-dir operations
1401          * by 30x or more...
1402          *
1403          * We try and optimize the sleep time against what the underlying disk
1404          * can do, instead of having a static sleep time.  This is usefull for
1405          * the case where our storage is so fast that it is more optimal to go
1406          * ahead and force a flush and wait for the transaction to be committed
1407          * than it is to wait for an arbitrary amount of time for new writers to
1408          * join the transaction.  We acheive this by measuring how long it takes
1409          * to commit a transaction, and compare it with how long this
1410          * transaction has been running, and if run time < commit time then we
1411          * sleep for the delta and commit.  This greatly helps super fast disks
1412          * that would see slowdowns as more threads started doing fsyncs.
1413          *
1414          * But don't do this if this process was the most recent one to
1415          * perform a synchronous write.  We do this to detect the case where a
1416          * single process is doing a stream of sync writes.  No point in waiting
1417          * for joiners in that case.
1418          */
1419         pid = current->pid;
1420         if (handle->h_sync && journal->j_last_sync_writer != pid) {
1421                 u64 commit_time, trans_time;
1422
1423                 journal->j_last_sync_writer = pid;
1424
1425                 spin_lock(&journal->j_state_lock);
1426                 commit_time = journal->j_average_commit_time;
1427                 spin_unlock(&journal->j_state_lock);
1428
1429                 trans_time = ktime_to_ns(ktime_sub(ktime_get(),
1430                                                    transaction->t_start_time));
1431
1432                 commit_time = min_t(u64, commit_time,
1433                                     1000*jiffies_to_usecs(1));
1434
1435                 if (trans_time < commit_time) {
1436                         ktime_t expires = ktime_add_ns(ktime_get(),
1437                                                        commit_time);
1438                         set_current_state(TASK_UNINTERRUPTIBLE);
1439                         schedule_hrtimeout(&expires, HRTIMER_MODE_ABS);
1440                 }
1441         }
1442
1443         current->journal_info = NULL;
1444         spin_lock(&journal->j_state_lock);
1445         spin_lock(&transaction->t_handle_lock);
1446         transaction->t_outstanding_credits -= handle->h_buffer_credits;
1447         transaction->t_updates--;
1448         if (!transaction->t_updates) {
1449                 wake_up(&journal->j_wait_updates);
1450                 if (journal->j_barrier_count)
1451                         wake_up(&journal->j_wait_transaction_locked);
1452         }
1453
1454         /*
1455          * If the handle is marked SYNC, we need to set another commit
1456          * going!  We also want to force a commit if the current
1457          * transaction is occupying too much of the log, or if the
1458          * transaction is too old now.
1459          */
1460         if (handle->h_sync ||
1461                         transaction->t_outstanding_credits >
1462                                 journal->j_max_transaction_buffers ||
1463                         time_after_eq(jiffies, transaction->t_expires)) {
1464                 /* Do this even for aborted journals: an abort still
1465                  * completes the commit thread, it just doesn't write
1466                  * anything to disk. */
1467                 tid_t tid = transaction->t_tid;
1468
1469                 spin_unlock(&transaction->t_handle_lock);
1470                 jbd_debug(2, "transaction too old, requesting commit for "
1471                                         "handle %p\n", handle);
1472                 /* This is non-blocking */
1473                 __log_start_commit(journal, transaction->t_tid);
1474                 spin_unlock(&journal->j_state_lock);
1475
1476                 /*
1477                  * Special case: JFS_SYNC synchronous updates require us
1478                  * to wait for the commit to complete.
1479                  */
1480                 if (handle->h_sync && !(current->flags & PF_MEMALLOC))
1481                         err = log_wait_commit(journal, tid);
1482         } else {
1483                 spin_unlock(&transaction->t_handle_lock);
1484                 spin_unlock(&journal->j_state_lock);
1485         }
1486
1487         lock_map_release(&handle->h_lockdep_map);
1488
1489         jbd_free_handle(handle);
1490         return err;
1491 }
1492
1493 /**
1494  * int journal_force_commit() - force any uncommitted transactions
1495  * @journal: journal to force
1496  *
1497  * For synchronous operations: force any uncommitted transactions
1498  * to disk.  May seem kludgy, but it reuses all the handle batching
1499  * code in a very simple manner.
1500  */
1501 int journal_force_commit(journal_t *journal)
1502 {
1503         handle_t *handle;
1504         int ret;
1505
1506         handle = journal_start(journal, 1);
1507         if (IS_ERR(handle)) {
1508                 ret = PTR_ERR(handle);
1509         } else {
1510                 handle->h_sync = 1;
1511                 ret = journal_stop(handle);
1512         }
1513         return ret;
1514 }
1515
1516 /*
1517  *
1518  * List management code snippets: various functions for manipulating the
1519  * transaction buffer lists.
1520  *
1521  */
1522
1523 /*
1524  * Append a buffer to a transaction list, given the transaction's list head
1525  * pointer.
1526  *
1527  * j_list_lock is held.
1528  *
1529  * jbd_lock_bh_state(jh2bh(jh)) is held.
1530  */
1531
1532 static inline void
1533 __blist_add_buffer(struct journal_head **list, struct journal_head *jh)
1534 {
1535         if (!*list) {
1536                 jh->b_tnext = jh->b_tprev = jh;
1537                 *list = jh;
1538         } else {
1539                 /* Insert at the tail of the list to preserve order */
1540                 struct journal_head *first = *list, *last = first->b_tprev;
1541                 jh->b_tprev = last;
1542                 jh->b_tnext = first;
1543                 last->b_tnext = first->b_tprev = jh;
1544         }
1545 }
1546
1547 /*
1548  * Remove a buffer from a transaction list, given the transaction's list
1549  * head pointer.
1550  *
1551  * Called with j_list_lock held, and the journal may not be locked.
1552  *
1553  * jbd_lock_bh_state(jh2bh(jh)) is held.
1554  */
1555
1556 static inline void
1557 __blist_del_buffer(struct journal_head **list, struct journal_head *jh)
1558 {
1559         if (*list == jh) {
1560                 *list = jh->b_tnext;
1561                 if (*list == jh)
1562                         *list = NULL;
1563         }
1564         jh->b_tprev->b_tnext = jh->b_tnext;
1565         jh->b_tnext->b_tprev = jh->b_tprev;
1566 }
1567
1568 /*
1569  * Remove a buffer from the appropriate transaction list.
1570  *
1571  * Note that this function can *change* the value of
1572  * bh->b_transaction->t_sync_datalist, t_buffers, t_forget,
1573  * t_iobuf_list, t_shadow_list, t_log_list or t_reserved_list.  If the caller
1574  * is holding onto a copy of one of thee pointers, it could go bad.
1575  * Generally the caller needs to re-read the pointer from the transaction_t.
1576  *
1577  * Called under j_list_lock.  The journal may not be locked.
1578  */
1579 static void __journal_temp_unlink_buffer(struct journal_head *jh)
1580 {
1581         struct journal_head **list = NULL;
1582         transaction_t *transaction;
1583         struct buffer_head *bh = jh2bh(jh);
1584
1585         J_ASSERT_JH(jh, jbd_is_locked_bh_state(bh));
1586         transaction = jh->b_transaction;
1587         if (transaction)
1588                 assert_spin_locked(&transaction->t_journal->j_list_lock);
1589
1590         J_ASSERT_JH(jh, jh->b_jlist < BJ_Types);
1591         if (jh->b_jlist != BJ_None)
1592                 J_ASSERT_JH(jh, transaction != NULL);
1593
1594         switch (jh->b_jlist) {
1595         case BJ_None:
1596                 return;
1597         case BJ_SyncData:
1598                 list = &transaction->t_sync_datalist;
1599                 break;
1600         case BJ_Metadata:
1601                 transaction->t_nr_buffers--;
1602                 J_ASSERT_JH(jh, transaction->t_nr_buffers >= 0);
1603                 list = &transaction->t_buffers;
1604                 break;
1605         case BJ_Forget:
1606                 list = &transaction->t_forget;
1607                 break;
1608         case BJ_IO:
1609                 list = &transaction->t_iobuf_list;
1610                 break;
1611         case BJ_Shadow:
1612                 list = &transaction->t_shadow_list;
1613                 break;
1614         case BJ_LogCtl:
1615                 list = &transaction->t_log_list;
1616                 break;
1617         case BJ_Reserved:
1618                 list = &transaction->t_reserved_list;
1619                 break;
1620         case BJ_Locked:
1621                 list = &transaction->t_locked_list;
1622                 break;
1623         }
1624
1625         __blist_del_buffer(list, jh);
1626         jh->b_jlist = BJ_None;
1627         if (test_clear_buffer_jbddirty(bh))
1628                 mark_buffer_dirty(bh);  /* Expose it to the VM */
1629 }
1630
1631 void __journal_unfile_buffer(struct journal_head *jh)
1632 {
1633         __journal_temp_unlink_buffer(jh);
1634         jh->b_transaction = NULL;
1635 }
1636
1637 void journal_unfile_buffer(journal_t *journal, struct journal_head *jh)
1638 {
1639         jbd_lock_bh_state(jh2bh(jh));
1640         spin_lock(&journal->j_list_lock);
1641         __journal_unfile_buffer(jh);
1642         spin_unlock(&journal->j_list_lock);
1643         jbd_unlock_bh_state(jh2bh(jh));
1644 }
1645
1646 /*
1647  * Called from journal_try_to_free_buffers().
1648  *
1649  * Called under jbd_lock_bh_state(bh)
1650  */
1651 static void
1652 __journal_try_to_free_buffer(journal_t *journal, struct buffer_head *bh)
1653 {
1654         struct journal_head *jh;
1655
1656         jh = bh2jh(bh);
1657
1658         if (buffer_locked(bh) || buffer_dirty(bh))
1659                 goto out;
1660
1661         if (jh->b_next_transaction != NULL)
1662                 goto out;
1663
1664         spin_lock(&journal->j_list_lock);
1665         if (jh->b_transaction != NULL && jh->b_cp_transaction == NULL) {
1666                 if (jh->b_jlist == BJ_SyncData || jh->b_jlist == BJ_Locked) {
1667                         /* A written-back ordered data buffer */
1668                         JBUFFER_TRACE(jh, "release data");
1669                         __journal_unfile_buffer(jh);
1670                         journal_remove_journal_head(bh);
1671                         __brelse(bh);
1672                 }
1673         } else if (jh->b_cp_transaction != NULL && jh->b_transaction == NULL) {
1674                 /* written-back checkpointed metadata buffer */
1675                 if (jh->b_jlist == BJ_None) {
1676                         JBUFFER_TRACE(jh, "remove from checkpoint list");
1677                         __journal_remove_checkpoint(jh);
1678                         journal_remove_journal_head(bh);
1679                         __brelse(bh);
1680                 }
1681         }
1682         spin_unlock(&journal->j_list_lock);
1683 out:
1684         return;
1685 }
1686
1687 /*
1688  * journal_try_to_free_buffers() could race with journal_commit_transaction()
1689  * The latter might still hold the a count on buffers when inspecting
1690  * them on t_syncdata_list or t_locked_list.
1691  *
1692  * journal_try_to_free_buffers() will call this function to
1693  * wait for the current transaction to finish syncing data buffers, before
1694  * tryinf to free that buffer.
1695  *
1696  * Called with journal->j_state_lock held.
1697  */
1698 static void journal_wait_for_transaction_sync_data(journal_t *journal)
1699 {
1700         transaction_t *transaction = NULL;
1701         tid_t tid;
1702
1703         spin_lock(&journal->j_state_lock);
1704         transaction = journal->j_committing_transaction;
1705
1706         if (!transaction) {
1707                 spin_unlock(&journal->j_state_lock);
1708                 return;
1709         }
1710
1711         tid = transaction->t_tid;
1712         spin_unlock(&journal->j_state_lock);
1713         log_wait_commit(journal, tid);
1714 }
1715
1716 /**
1717  * int journal_try_to_free_buffers() - try to free page buffers.
1718  * @journal: journal for operation
1719  * @page: to try and free
1720  * @gfp_mask: we use the mask to detect how hard should we try to release
1721  * buffers. If __GFP_WAIT and __GFP_FS is set, we wait for commit code to
1722  * release the buffers.
1723  *
1724  *
1725  * For all the buffers on this page,
1726  * if they are fully written out ordered data, move them onto BUF_CLEAN
1727  * so try_to_free_buffers() can reap them.
1728  *
1729  * This function returns non-zero if we wish try_to_free_buffers()
1730  * to be called. We do this if the page is releasable by try_to_free_buffers().
1731  * We also do it if the page has locked or dirty buffers and the caller wants
1732  * us to perform sync or async writeout.
1733  *
1734  * This complicates JBD locking somewhat.  We aren't protected by the
1735  * BKL here.  We wish to remove the buffer from its committing or
1736  * running transaction's ->t_datalist via __journal_unfile_buffer.
1737  *
1738  * This may *change* the value of transaction_t->t_datalist, so anyone
1739  * who looks at t_datalist needs to lock against this function.
1740  *
1741  * Even worse, someone may be doing a journal_dirty_data on this
1742  * buffer.  So we need to lock against that.  journal_dirty_data()
1743  * will come out of the lock with the buffer dirty, which makes it
1744  * ineligible for release here.
1745  *
1746  * Who else is affected by this?  hmm...  Really the only contender
1747  * is do_get_write_access() - it could be looking at the buffer while
1748  * journal_try_to_free_buffer() is changing its state.  But that
1749  * cannot happen because we never reallocate freed data as metadata
1750  * while the data is part of a transaction.  Yes?
1751  *
1752  * Return 0 on failure, 1 on success
1753  */
1754 int journal_try_to_free_buffers(journal_t *journal,
1755                                 struct page *page, gfp_t gfp_mask)
1756 {
1757         struct buffer_head *head;
1758         struct buffer_head *bh;
1759         int ret = 0;
1760
1761         J_ASSERT(PageLocked(page));
1762
1763         head = page_buffers(page);
1764         bh = head;
1765         do {
1766                 struct journal_head *jh;
1767
1768                 /*
1769                  * We take our own ref against the journal_head here to avoid
1770                  * having to add tons of locking around each instance of
1771                  * journal_remove_journal_head() and journal_put_journal_head().
1772                  */
1773                 jh = journal_grab_journal_head(bh);
1774                 if (!jh)
1775                         continue;
1776
1777                 jbd_lock_bh_state(bh);
1778                 __journal_try_to_free_buffer(journal, bh);
1779                 journal_put_journal_head(jh);
1780                 jbd_unlock_bh_state(bh);
1781                 if (buffer_jbd(bh))
1782                         goto busy;
1783         } while ((bh = bh->b_this_page) != head);
1784
1785         ret = try_to_free_buffers(page);
1786
1787         /*
1788          * There are a number of places where journal_try_to_free_buffers()
1789          * could race with journal_commit_transaction(), the later still
1790          * holds the reference to the buffers to free while processing them.
1791          * try_to_free_buffers() failed to free those buffers. Some of the
1792          * caller of releasepage() request page buffers to be dropped, otherwise
1793          * treat the fail-to-free as errors (such as generic_file_direct_IO())
1794          *
1795          * So, if the caller of try_to_release_page() wants the synchronous
1796          * behaviour(i.e make sure buffers are dropped upon return),
1797          * let's wait for the current transaction to finish flush of
1798          * dirty data buffers, then try to free those buffers again,
1799          * with the journal locked.
1800          */
1801         if (ret == 0 && (gfp_mask & __GFP_WAIT) && (gfp_mask & __GFP_FS)) {
1802                 journal_wait_for_transaction_sync_data(journal);
1803                 ret = try_to_free_buffers(page);
1804         }
1805
1806 busy:
1807         return ret;
1808 }
1809
1810 /*
1811  * This buffer is no longer needed.  If it is on an older transaction's
1812  * checkpoint list we need to record it on this transaction's forget list
1813  * to pin this buffer (and hence its checkpointing transaction) down until
1814  * this transaction commits.  If the buffer isn't on a checkpoint list, we
1815  * release it.
1816  * Returns non-zero if JBD no longer has an interest in the buffer.
1817  *
1818  * Called under j_list_lock.
1819  *
1820  * Called under jbd_lock_bh_state(bh).
1821  */
1822 static int __dispose_buffer(struct journal_head *jh, transaction_t *transaction)
1823 {
1824         int may_free = 1;
1825         struct buffer_head *bh = jh2bh(jh);
1826
1827         __journal_unfile_buffer(jh);
1828
1829         if (jh->b_cp_transaction) {
1830                 JBUFFER_TRACE(jh, "on running+cp transaction");
1831                 __journal_file_buffer(jh, transaction, BJ_Forget);
1832                 clear_buffer_jbddirty(bh);
1833                 may_free = 0;
1834         } else {
1835                 JBUFFER_TRACE(jh, "on running transaction");
1836                 journal_remove_journal_head(bh);
1837                 __brelse(bh);
1838         }
1839         return may_free;
1840 }
1841
1842 /*
1843  * journal_invalidatepage
1844  *
1845  * This code is tricky.  It has a number of cases to deal with.
1846  *
1847  * There are two invariants which this code relies on:
1848  *
1849  * i_size must be updated on disk before we start calling invalidatepage on the
1850  * data.
1851  *
1852  *  This is done in ext3 by defining an ext3_setattr method which
1853  *  updates i_size before truncate gets going.  By maintaining this
1854  *  invariant, we can be sure that it is safe to throw away any buffers
1855  *  attached to the current transaction: once the transaction commits,
1856  *  we know that the data will not be needed.
1857  *
1858  *  Note however that we can *not* throw away data belonging to the
1859  *  previous, committing transaction!
1860  *
1861  * Any disk blocks which *are* part of the previous, committing
1862  * transaction (and which therefore cannot be discarded immediately) are
1863  * not going to be reused in the new running transaction
1864  *
1865  *  The bitmap committed_data images guarantee this: any block which is
1866  *  allocated in one transaction and removed in the next will be marked
1867  *  as in-use in the committed_data bitmap, so cannot be reused until
1868  *  the next transaction to delete the block commits.  This means that
1869  *  leaving committing buffers dirty is quite safe: the disk blocks
1870  *  cannot be reallocated to a different file and so buffer aliasing is
1871  *  not possible.
1872  *
1873  *
1874  * The above applies mainly to ordered data mode.  In writeback mode we
1875  * don't make guarantees about the order in which data hits disk --- in
1876  * particular we don't guarantee that new dirty data is flushed before
1877  * transaction commit --- so it is always safe just to discard data
1878  * immediately in that mode.  --sct
1879  */
1880
1881 /*
1882  * The journal_unmap_buffer helper function returns zero if the buffer
1883  * concerned remains pinned as an anonymous buffer belonging to an older
1884  * transaction.
1885  *
1886  * We're outside-transaction here.  Either or both of j_running_transaction
1887  * and j_committing_transaction may be NULL.
1888  */
1889 static int journal_unmap_buffer(journal_t *journal, struct buffer_head *bh)
1890 {
1891         transaction_t *transaction;
1892         struct journal_head *jh;
1893         int may_free = 1;
1894         int ret;
1895
1896         BUFFER_TRACE(bh, "entry");
1897
1898         /*
1899          * It is safe to proceed here without the j_list_lock because the
1900          * buffers cannot be stolen by try_to_free_buffers as long as we are
1901          * holding the page lock. --sct
1902          */
1903
1904         if (!buffer_jbd(bh))
1905                 goto zap_buffer_unlocked;
1906
1907         spin_lock(&journal->j_state_lock);
1908         jbd_lock_bh_state(bh);
1909         spin_lock(&journal->j_list_lock);
1910
1911         jh = journal_grab_journal_head(bh);
1912         if (!jh)
1913                 goto zap_buffer_no_jh;
1914
1915         transaction = jh->b_transaction;
1916         if (transaction == NULL) {
1917                 /* First case: not on any transaction.  If it
1918                  * has no checkpoint link, then we can zap it:
1919                  * it's a writeback-mode buffer so we don't care
1920                  * if it hits disk safely. */
1921                 if (!jh->b_cp_transaction) {
1922                         JBUFFER_TRACE(jh, "not on any transaction: zap");
1923                         goto zap_buffer;
1924                 }
1925
1926                 if (!buffer_dirty(bh)) {
1927                         /* bdflush has written it.  We can drop it now */
1928                         goto zap_buffer;
1929                 }
1930
1931                 /* OK, it must be in the journal but still not
1932                  * written fully to disk: it's metadata or
1933                  * journaled data... */
1934
1935                 if (journal->j_running_transaction) {
1936                         /* ... and once the current transaction has
1937                          * committed, the buffer won't be needed any
1938                          * longer. */
1939                         JBUFFER_TRACE(jh, "checkpointed: add to BJ_Forget");
1940                         ret = __dispose_buffer(jh,
1941                                         journal->j_running_transaction);
1942                         journal_put_journal_head(jh);
1943                         spin_unlock(&journal->j_list_lock);
1944                         jbd_unlock_bh_state(bh);
1945                         spin_unlock(&journal->j_state_lock);
1946                         return ret;
1947                 } else {
1948                         /* There is no currently-running transaction. So the
1949                          * orphan record which we wrote for this file must have
1950                          * passed into commit.  We must attach this buffer to
1951                          * the committing transaction, if it exists. */
1952                         if (journal->j_committing_transaction) {
1953                                 JBUFFER_TRACE(jh, "give to committing trans");
1954                                 ret = __dispose_buffer(jh,
1955                                         journal->j_committing_transaction);
1956                                 journal_put_journal_head(jh);
1957                                 spin_unlock(&journal->j_list_lock);
1958                                 jbd_unlock_bh_state(bh);
1959                                 spin_unlock(&journal->j_state_lock);
1960                                 return ret;
1961                         } else {
1962                                 /* The orphan record's transaction has
1963                                  * committed.  We can cleanse this buffer */
1964                                 clear_buffer_jbddirty(bh);
1965                                 goto zap_buffer;
1966                         }
1967                 }
1968         } else if (transaction == journal->j_committing_transaction) {
1969                 JBUFFER_TRACE(jh, "on committing transaction");
1970                 if (jh->b_jlist == BJ_Locked) {
1971                         /*
1972                          * The buffer is on the committing transaction's locked
1973                          * list.  We have the buffer locked, so I/O has
1974                          * completed.  So we can nail the buffer now.
1975                          */
1976                         may_free = __dispose_buffer(jh, transaction);
1977                         goto zap_buffer;
1978                 }
1979                 /*
1980                  * If it is committing, we simply cannot touch it.  We
1981                  * can remove it's next_transaction pointer from the
1982                  * running transaction if that is set, but nothing
1983                  * else. */
1984                 set_buffer_freed(bh);
1985                 if (jh->b_next_transaction) {
1986                         J_ASSERT(jh->b_next_transaction ==
1987                                         journal->j_running_transaction);
1988                         jh->b_next_transaction = NULL;
1989                 }
1990                 journal_put_journal_head(jh);
1991                 spin_unlock(&journal->j_list_lock);
1992                 jbd_unlock_bh_state(bh);
1993                 spin_unlock(&journal->j_state_lock);
1994                 return 0;
1995         } else {
1996                 /* Good, the buffer belongs to the running transaction.
1997                  * We are writing our own transaction's data, not any
1998                  * previous one's, so it is safe to throw it away
1999                  * (remember that we expect the filesystem to have set
2000                  * i_size already for this truncate so recovery will not
2001                  * expose the disk blocks we are discarding here.) */
2002                 J_ASSERT_JH(jh, transaction == journal->j_running_transaction);
2003                 JBUFFER_TRACE(jh, "on running transaction");
2004                 may_free = __dispose_buffer(jh, transaction);
2005         }
2006
2007 zap_buffer:
2008         journal_put_journal_head(jh);
2009 zap_buffer_no_jh:
2010         spin_unlock(&journal->j_list_lock);
2011         jbd_unlock_bh_state(bh);
2012         spin_unlock(&journal->j_state_lock);
2013 zap_buffer_unlocked:
2014         clear_buffer_dirty(bh);
2015         J_ASSERT_BH(bh, !buffer_jbddirty(bh));
2016         clear_buffer_mapped(bh);
2017         clear_buffer_req(bh);
2018         clear_buffer_new(bh);
2019         bh->b_bdev = NULL;
2020         return may_free;
2021 }
2022
2023 /**
2024  * void journal_invalidatepage() - invalidate a journal page
2025  * @journal: journal to use for flush
2026  * @page:    page to flush
2027  * @offset:  length of page to invalidate.
2028  *
2029  * Reap page buffers containing data after offset in page.
2030  */
2031 void journal_invalidatepage(journal_t *journal,
2032                       struct page *page,
2033                       unsigned long offset)
2034 {
2035         struct buffer_head *head, *bh, *next;
2036         unsigned int curr_off = 0;
2037         int may_free = 1;
2038
2039         if (!PageLocked(page))
2040                 BUG();
2041         if (!page_has_buffers(page))
2042                 return;
2043
2044         /* We will potentially be playing with lists other than just the
2045          * data lists (especially for journaled data mode), so be
2046          * cautious in our locking. */
2047
2048         head = bh = page_buffers(page);
2049         do {
2050                 unsigned int next_off = curr_off + bh->b_size;
2051                 next = bh->b_this_page;
2052
2053                 if (offset <= curr_off) {
2054                         /* This block is wholly outside the truncation point */
2055                         lock_buffer(bh);
2056                         may_free &= journal_unmap_buffer(journal, bh);
2057                         unlock_buffer(bh);
2058                 }
2059                 curr_off = next_off;
2060                 bh = next;
2061
2062         } while (bh != head);
2063
2064         if (!offset) {
2065                 if (may_free && try_to_free_buffers(page))
2066                         J_ASSERT(!page_has_buffers(page));
2067         }
2068 }
2069
2070 /*
2071  * File a buffer on the given transaction list.
2072  */
2073 void __journal_file_buffer(struct journal_head *jh,
2074                         transaction_t *transaction, int jlist)
2075 {
2076         struct journal_head **list = NULL;
2077         int was_dirty = 0;
2078         struct buffer_head *bh = jh2bh(jh);
2079
2080         J_ASSERT_JH(jh, jbd_is_locked_bh_state(bh));
2081         assert_spin_locked(&transaction->t_journal->j_list_lock);
2082
2083         J_ASSERT_JH(jh, jh->b_jlist < BJ_Types);
2084         J_ASSERT_JH(jh, jh->b_transaction == transaction ||
2085                                 jh->b_transaction == NULL);
2086
2087         if (jh->b_transaction && jh->b_jlist == jlist)
2088                 return;
2089
2090         /* The following list of buffer states needs to be consistent
2091          * with __jbd_unexpected_dirty_buffer()'s handling of dirty
2092          * state. */
2093
2094         if (jlist == BJ_Metadata || jlist == BJ_Reserved ||
2095             jlist == BJ_Shadow || jlist == BJ_Forget) {
2096                 if (test_clear_buffer_dirty(bh) ||
2097                     test_clear_buffer_jbddirty(bh))
2098                         was_dirty = 1;
2099         }
2100
2101         if (jh->b_transaction)
2102                 __journal_temp_unlink_buffer(jh);
2103         jh->b_transaction = transaction;
2104
2105         switch (jlist) {
2106         case BJ_None:
2107                 J_ASSERT_JH(jh, !jh->b_committed_data);
2108                 J_ASSERT_JH(jh, !jh->b_frozen_data);
2109                 return;
2110         case BJ_SyncData:
2111                 list = &transaction->t_sync_datalist;
2112                 break;
2113         case BJ_Metadata:
2114                 transaction->t_nr_buffers++;
2115                 list = &transaction->t_buffers;
2116                 break;
2117         case BJ_Forget:
2118                 list = &transaction->t_forget;
2119                 break;
2120         case BJ_IO:
2121                 list = &transaction->t_iobuf_list;
2122                 break;
2123         case BJ_Shadow:
2124                 list = &transaction->t_shadow_list;
2125                 break;
2126         case BJ_LogCtl:
2127                 list = &transaction->t_log_list;
2128                 break;
2129         case BJ_Reserved:
2130                 list = &transaction->t_reserved_list;
2131                 break;
2132         case BJ_Locked:
2133                 list =  &transaction->t_locked_list;
2134                 break;
2135         }
2136
2137         __blist_add_buffer(list, jh);
2138         jh->b_jlist = jlist;
2139
2140         if (was_dirty)
2141                 set_buffer_jbddirty(bh);
2142 }
2143
2144 void journal_file_buffer(struct journal_head *jh,
2145                                 transaction_t *transaction, int jlist)
2146 {
2147         jbd_lock_bh_state(jh2bh(jh));
2148         spin_lock(&transaction->t_journal->j_list_lock);
2149         __journal_file_buffer(jh, transaction, jlist);
2150         spin_unlock(&transaction->t_journal->j_list_lock);
2151         jbd_unlock_bh_state(jh2bh(jh));
2152 }
2153
2154 /*
2155  * Remove a buffer from its current buffer list in preparation for
2156  * dropping it from its current transaction entirely.  If the buffer has
2157  * already started to be used by a subsequent transaction, refile the
2158  * buffer on that transaction's metadata list.
2159  *
2160  * Called under journal->j_list_lock
2161  *
2162  * Called under jbd_lock_bh_state(jh2bh(jh))
2163  */
2164 void __journal_refile_buffer(struct journal_head *jh)
2165 {
2166         int was_dirty;
2167         struct buffer_head *bh = jh2bh(jh);
2168
2169         J_ASSERT_JH(jh, jbd_is_locked_bh_state(bh));
2170         if (jh->b_transaction)
2171                 assert_spin_locked(&jh->b_transaction->t_journal->j_list_lock);
2172
2173         /* If the buffer is now unused, just drop it. */
2174         if (jh->b_next_transaction == NULL) {
2175                 __journal_unfile_buffer(jh);
2176                 return;
2177         }
2178
2179         /*
2180          * It has been modified by a later transaction: add it to the new
2181          * transaction's metadata list.
2182          */
2183
2184         was_dirty = test_clear_buffer_jbddirty(bh);
2185         __journal_temp_unlink_buffer(jh);
2186         jh->b_transaction = jh->b_next_transaction;
2187         jh->b_next_transaction = NULL;
2188         __journal_file_buffer(jh, jh->b_transaction,
2189                                 jh->b_modified ? BJ_Metadata : BJ_Reserved);
2190         J_ASSERT_JH(jh, jh->b_transaction->t_state == T_RUNNING);
2191
2192         if (was_dirty)
2193                 set_buffer_jbddirty(bh);
2194 }
2195
2196 /*
2197  * For the unlocked version of this call, also make sure that any
2198  * hanging journal_head is cleaned up if necessary.
2199  *
2200  * __journal_refile_buffer is usually called as part of a single locked
2201  * operation on a buffer_head, in which the caller is probably going to
2202  * be hooking the journal_head onto other lists.  In that case it is up
2203  * to the caller to remove the journal_head if necessary.  For the
2204  * unlocked journal_refile_buffer call, the caller isn't going to be
2205  * doing anything else to the buffer so we need to do the cleanup
2206  * ourselves to avoid a jh leak.
2207  *
2208  * *** The journal_head may be freed by this call! ***
2209  */
2210 void journal_refile_buffer(journal_t *journal, struct journal_head *jh)
2211 {
2212         struct buffer_head *bh = jh2bh(jh);
2213
2214         jbd_lock_bh_state(bh);
2215         spin_lock(&journal->j_list_lock);
2216
2217         __journal_refile_buffer(jh);
2218         jbd_unlock_bh_state(bh);
2219         journal_remove_journal_head(bh);
2220
2221         spin_unlock(&journal->j_list_lock);
2222         __brelse(bh);
2223 }