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