Merge branch 'master' of /home/trondmy/kernel/linux-2.6/ into merge_linus
[linux-2.6.git] / fs / nfs / direct.c
1 /*
2  * linux/fs/nfs/direct.c
3  *
4  * Copyright (C) 2003 by Chuck Lever <cel@netapp.com>
5  *
6  * High-performance uncached I/O for the Linux NFS client
7  *
8  * There are important applications whose performance or correctness
9  * depends on uncached access to file data.  Database clusters
10  * (multiple copies of the same instance running on separate hosts)
11  * implement their own cache coherency protocol that subsumes file
12  * system cache protocols.  Applications that process datasets
13  * considerably larger than the client's memory do not always benefit
14  * from a local cache.  A streaming video server, for instance, has no
15  * need to cache the contents of a file.
16  *
17  * When an application requests uncached I/O, all read and write requests
18  * are made directly to the server; data stored or fetched via these
19  * requests is not cached in the Linux page cache.  The client does not
20  * correct unaligned requests from applications.  All requested bytes are
21  * held on permanent storage before a direct write system call returns to
22  * an application.
23  *
24  * Solaris implements an uncached I/O facility called directio() that
25  * is used for backups and sequential I/O to very large files.  Solaris
26  * also supports uncaching whole NFS partitions with "-o forcedirectio,"
27  * an undocumented mount option.
28  *
29  * Designed by Jeff Kimmel, Chuck Lever, and Trond Myklebust, with
30  * help from Andrew Morton.
31  *
32  * 18 Dec 2001  Initial implementation for 2.4  --cel
33  * 08 Jul 2002  Version for 2.4.19, with bug fixes --trondmy
34  * 08 Jun 2003  Port to 2.5 APIs  --cel
35  * 31 Mar 2004  Handle direct I/O without VFS support  --cel
36  * 15 Sep 2004  Parallel async reads  --cel
37  * 04 May 2005  support O_DIRECT with aio  --cel
38  *
39  */
40
41 #include <linux/errno.h>
42 #include <linux/sched.h>
43 #include <linux/kernel.h>
44 #include <linux/smp_lock.h>
45 #include <linux/file.h>
46 #include <linux/pagemap.h>
47 #include <linux/kref.h>
48
49 #include <linux/nfs_fs.h>
50 #include <linux/nfs_page.h>
51 #include <linux/sunrpc/clnt.h>
52
53 #include <asm/system.h>
54 #include <asm/uaccess.h>
55 #include <asm/atomic.h>
56
57 #include "iostat.h"
58
59 #define NFSDBG_FACILITY         NFSDBG_VFS
60
61 static struct kmem_cache *nfs_direct_cachep;
62
63 /*
64  * This represents a set of asynchronous requests that we're waiting on
65  */
66 struct nfs_direct_req {
67         struct kref             kref;           /* release manager */
68
69         /* I/O parameters */
70         struct nfs_open_context *ctx;           /* file open context info */
71         struct kiocb *          iocb;           /* controlling i/o request */
72         struct inode *          inode;          /* target file of i/o */
73
74         /* completion state */
75         atomic_t                io_count;       /* i/os we're waiting for */
76         spinlock_t              lock;           /* protect completion state */
77         ssize_t                 count,          /* bytes actually processed */
78                                 error;          /* any reported error */
79         struct completion       completion;     /* wait for i/o completion */
80
81         /* commit state */
82         struct list_head        rewrite_list;   /* saved nfs_write_data structs */
83         struct nfs_write_data * commit_data;    /* special write_data for commits */
84         int                     flags;
85 #define NFS_ODIRECT_DO_COMMIT           (1)     /* an unstable reply was received */
86 #define NFS_ODIRECT_RESCHED_WRITES      (2)     /* write verification failed */
87         struct nfs_writeverf    verf;           /* unstable write verifier */
88 };
89
90 static void nfs_direct_write_complete(struct nfs_direct_req *dreq, struct inode *inode);
91 static const struct rpc_call_ops nfs_write_direct_ops;
92
93 static inline void get_dreq(struct nfs_direct_req *dreq)
94 {
95         atomic_inc(&dreq->io_count);
96 }
97
98 static inline int put_dreq(struct nfs_direct_req *dreq)
99 {
100         return atomic_dec_and_test(&dreq->io_count);
101 }
102
103 /**
104  * nfs_direct_IO - NFS address space operation for direct I/O
105  * @rw: direction (read or write)
106  * @iocb: target I/O control block
107  * @iov: array of vectors that define I/O buffer
108  * @pos: offset in file to begin the operation
109  * @nr_segs: size of iovec array
110  *
111  * The presence of this routine in the address space ops vector means
112  * the NFS client supports direct I/O.  However, we shunt off direct
113  * read and write requests before the VFS gets them, so this method
114  * should never be called.
115  */
116 ssize_t nfs_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov, loff_t pos, unsigned long nr_segs)
117 {
118         dprintk("NFS: nfs_direct_IO (%s) off/no(%Ld/%lu) EINVAL\n",
119                         iocb->ki_filp->f_dentry->d_name.name,
120                         (long long) pos, nr_segs);
121
122         return -EINVAL;
123 }
124
125 static void nfs_direct_dirty_pages(struct page **pages, int npages)
126 {
127         int i;
128         for (i = 0; i < npages; i++) {
129                 struct page *page = pages[i];
130                 if (!PageCompound(page))
131                         set_page_dirty_lock(page);
132         }
133 }
134
135 static void nfs_direct_release_pages(struct page **pages, int npages)
136 {
137         int i;
138         for (i = 0; i < npages; i++)
139                 page_cache_release(pages[i]);
140 }
141
142 static inline struct nfs_direct_req *nfs_direct_req_alloc(void)
143 {
144         struct nfs_direct_req *dreq;
145
146         dreq = kmem_cache_alloc(nfs_direct_cachep, GFP_KERNEL);
147         if (!dreq)
148                 return NULL;
149
150         kref_init(&dreq->kref);
151         kref_get(&dreq->kref);
152         init_completion(&dreq->completion);
153         INIT_LIST_HEAD(&dreq->rewrite_list);
154         dreq->iocb = NULL;
155         dreq->ctx = NULL;
156         spin_lock_init(&dreq->lock);
157         atomic_set(&dreq->io_count, 0);
158         dreq->count = 0;
159         dreq->error = 0;
160         dreq->flags = 0;
161
162         return dreq;
163 }
164
165 static void nfs_direct_req_release(struct kref *kref)
166 {
167         struct nfs_direct_req *dreq = container_of(kref, struct nfs_direct_req, kref);
168
169         if (dreq->ctx != NULL)
170                 put_nfs_open_context(dreq->ctx);
171         kmem_cache_free(nfs_direct_cachep, dreq);
172 }
173
174 /*
175  * Collects and returns the final error value/byte-count.
176  */
177 static ssize_t nfs_direct_wait(struct nfs_direct_req *dreq)
178 {
179         ssize_t result = -EIOCBQUEUED;
180
181         /* Async requests don't wait here */
182         if (dreq->iocb)
183                 goto out;
184
185         result = wait_for_completion_interruptible(&dreq->completion);
186
187         if (!result)
188                 result = dreq->error;
189         if (!result)
190                 result = dreq->count;
191
192 out:
193         kref_put(&dreq->kref, nfs_direct_req_release);
194         return (ssize_t) result;
195 }
196
197 /*
198  * Synchronous I/O uses a stack-allocated iocb.  Thus we can't trust
199  * the iocb is still valid here if this is a synchronous request.
200  */
201 static void nfs_direct_complete(struct nfs_direct_req *dreq)
202 {
203         if (dreq->iocb) {
204                 long res = (long) dreq->error;
205                 if (!res)
206                         res = (long) dreq->count;
207                 aio_complete(dreq->iocb, res, 0);
208         }
209         complete_all(&dreq->completion);
210
211         kref_put(&dreq->kref, nfs_direct_req_release);
212 }
213
214 /*
215  * We must hold a reference to all the pages in this direct read request
216  * until the RPCs complete.  This could be long *after* we are woken up in
217  * nfs_direct_wait (for instance, if someone hits ^C on a slow server).
218  */
219 static void nfs_direct_read_result(struct rpc_task *task, void *calldata)
220 {
221         struct nfs_read_data *data = calldata;
222         struct nfs_direct_req *dreq = (struct nfs_direct_req *) data->req;
223
224         if (nfs_readpage_result(task, data) != 0)
225                 return;
226
227         nfs_direct_dirty_pages(data->pagevec, data->npages);
228         nfs_direct_release_pages(data->pagevec, data->npages);
229
230         spin_lock(&dreq->lock);
231
232         if (likely(task->tk_status >= 0))
233                 dreq->count += data->res.count;
234         else
235                 dreq->error = task->tk_status;
236
237         spin_unlock(&dreq->lock);
238
239         if (put_dreq(dreq))
240                 nfs_direct_complete(dreq);
241 }
242
243 static const struct rpc_call_ops nfs_read_direct_ops = {
244         .rpc_call_done = nfs_direct_read_result,
245         .rpc_release = nfs_readdata_release,
246 };
247
248 /*
249  * For each rsize'd chunk of the user's buffer, dispatch an NFS READ
250  * operation.  If nfs_readdata_alloc() or get_user_pages() fails,
251  * bail and stop sending more reads.  Read length accounting is
252  * handled automatically by nfs_direct_read_result().  Otherwise, if
253  * no requests have been sent, just return an error.
254  */
255 static ssize_t nfs_direct_read_schedule(struct nfs_direct_req *dreq, unsigned long user_addr, size_t count, loff_t pos)
256 {
257         struct nfs_open_context *ctx = dreq->ctx;
258         struct inode *inode = ctx->dentry->d_inode;
259         size_t rsize = NFS_SERVER(inode)->rsize;
260         unsigned int pgbase;
261         int result;
262         ssize_t started = 0;
263
264         get_dreq(dreq);
265
266         do {
267                 struct nfs_read_data *data;
268                 size_t bytes;
269
270                 pgbase = user_addr & ~PAGE_MASK;
271                 bytes = min(rsize,count);
272
273                 result = -ENOMEM;
274                 data = nfs_readdata_alloc(pgbase + bytes);
275                 if (unlikely(!data))
276                         break;
277
278                 down_read(&current->mm->mmap_sem);
279                 result = get_user_pages(current, current->mm, user_addr,
280                                         data->npages, 1, 0, data->pagevec, NULL);
281                 up_read(&current->mm->mmap_sem);
282                 if (unlikely(result < data->npages)) {
283                         if (result > 0)
284                                 nfs_direct_release_pages(data->pagevec, result);
285                         nfs_readdata_release(data);
286                         break;
287                 }
288
289                 get_dreq(dreq);
290
291                 data->req = (struct nfs_page *) dreq;
292                 data->inode = inode;
293                 data->cred = ctx->cred;
294                 data->args.fh = NFS_FH(inode);
295                 data->args.context = ctx;
296                 data->args.offset = pos;
297                 data->args.pgbase = pgbase;
298                 data->args.pages = data->pagevec;
299                 data->args.count = bytes;
300                 data->res.fattr = &data->fattr;
301                 data->res.eof = 0;
302                 data->res.count = bytes;
303
304                 rpc_init_task(&data->task, NFS_CLIENT(inode), RPC_TASK_ASYNC,
305                                 &nfs_read_direct_ops, data);
306                 NFS_PROTO(inode)->read_setup(data);
307
308                 data->task.tk_cookie = (unsigned long) inode;
309
310                 rpc_execute(&data->task);
311
312                 dfprintk(VFS, "NFS: %5u initiated direct read call (req %s/%Ld, %zu bytes @ offset %Lu)\n",
313                                 data->task.tk_pid,
314                                 inode->i_sb->s_id,
315                                 (long long)NFS_FILEID(inode),
316                                 bytes,
317                                 (unsigned long long)data->args.offset);
318
319                 started += bytes;
320                 user_addr += bytes;
321                 pos += bytes;
322                 /* FIXME: Remove this unnecessary math from final patch */
323                 pgbase += bytes;
324                 pgbase &= ~PAGE_MASK;
325                 BUG_ON(pgbase != (user_addr & ~PAGE_MASK));
326
327                 count -= bytes;
328         } while (count != 0);
329
330         if (put_dreq(dreq))
331                 nfs_direct_complete(dreq);
332
333         if (started)
334                 return 0;
335         return result < 0 ? (ssize_t) result : -EFAULT;
336 }
337
338 static ssize_t nfs_direct_read(struct kiocb *iocb, unsigned long user_addr, size_t count, loff_t pos)
339 {
340         ssize_t result = 0;
341         sigset_t oldset;
342         struct inode *inode = iocb->ki_filp->f_mapping->host;
343         struct rpc_clnt *clnt = NFS_CLIENT(inode);
344         struct nfs_direct_req *dreq;
345
346         dreq = nfs_direct_req_alloc();
347         if (!dreq)
348                 return -ENOMEM;
349
350         dreq->inode = inode;
351         dreq->ctx = get_nfs_open_context((struct nfs_open_context *)iocb->ki_filp->private_data);
352         if (!is_sync_kiocb(iocb))
353                 dreq->iocb = iocb;
354
355         nfs_add_stats(inode, NFSIOS_DIRECTREADBYTES, count);
356         rpc_clnt_sigmask(clnt, &oldset);
357         result = nfs_direct_read_schedule(dreq, user_addr, count, pos);
358         if (!result)
359                 result = nfs_direct_wait(dreq);
360         rpc_clnt_sigunmask(clnt, &oldset);
361
362         return result;
363 }
364
365 static void nfs_direct_free_writedata(struct nfs_direct_req *dreq)
366 {
367         while (!list_empty(&dreq->rewrite_list)) {
368                 struct nfs_write_data *data = list_entry(dreq->rewrite_list.next, struct nfs_write_data, pages);
369                 list_del(&data->pages);
370                 nfs_direct_release_pages(data->pagevec, data->npages);
371                 nfs_writedata_release(data);
372         }
373 }
374
375 #if defined(CONFIG_NFS_V3) || defined(CONFIG_NFS_V4)
376 static void nfs_direct_write_reschedule(struct nfs_direct_req *dreq)
377 {
378         struct inode *inode = dreq->inode;
379         struct list_head *p;
380         struct nfs_write_data *data;
381
382         dreq->count = 0;
383         get_dreq(dreq);
384
385         list_for_each(p, &dreq->rewrite_list) {
386                 data = list_entry(p, struct nfs_write_data, pages);
387
388                 get_dreq(dreq);
389
390                 /*
391                  * Reset data->res.
392                  */
393                 nfs_fattr_init(&data->fattr);
394                 data->res.count = data->args.count;
395                 memset(&data->verf, 0, sizeof(data->verf));
396
397                 /*
398                  * Reuse data->task; data->args should not have changed
399                  * since the original request was sent.
400                  */
401                 rpc_init_task(&data->task, NFS_CLIENT(inode), RPC_TASK_ASYNC,
402                                 &nfs_write_direct_ops, data);
403                 NFS_PROTO(inode)->write_setup(data, FLUSH_STABLE);
404
405                 data->task.tk_priority = RPC_PRIORITY_NORMAL;
406                 data->task.tk_cookie = (unsigned long) inode;
407
408                 /*
409                  * We're called via an RPC callback, so BKL is already held.
410                  */
411                 rpc_execute(&data->task);
412
413                 dprintk("NFS: %5u rescheduled direct write call (req %s/%Ld, %u bytes @ offset %Lu)\n",
414                                 data->task.tk_pid,
415                                 inode->i_sb->s_id,
416                                 (long long)NFS_FILEID(inode),
417                                 data->args.count,
418                                 (unsigned long long)data->args.offset);
419         }
420
421         if (put_dreq(dreq))
422                 nfs_direct_write_complete(dreq, inode);
423 }
424
425 static void nfs_direct_commit_result(struct rpc_task *task, void *calldata)
426 {
427         struct nfs_write_data *data = calldata;
428         struct nfs_direct_req *dreq = (struct nfs_direct_req *) data->req;
429
430         /* Call the NFS version-specific code */
431         if (NFS_PROTO(data->inode)->commit_done(task, data) != 0)
432                 return;
433         if (unlikely(task->tk_status < 0)) {
434                 dreq->error = task->tk_status;
435                 dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
436         }
437         if (memcmp(&dreq->verf, &data->verf, sizeof(data->verf))) {
438                 dprintk("NFS: %5u commit verify failed\n", task->tk_pid);
439                 dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
440         }
441
442         dprintk("NFS: %5u commit returned %d\n", task->tk_pid, task->tk_status);
443         nfs_direct_write_complete(dreq, data->inode);
444 }
445
446 static const struct rpc_call_ops nfs_commit_direct_ops = {
447         .rpc_call_done = nfs_direct_commit_result,
448         .rpc_release = nfs_commit_release,
449 };
450
451 static void nfs_direct_commit_schedule(struct nfs_direct_req *dreq)
452 {
453         struct nfs_write_data *data = dreq->commit_data;
454
455         data->inode = dreq->inode;
456         data->cred = dreq->ctx->cred;
457
458         data->args.fh = NFS_FH(data->inode);
459         data->args.offset = 0;
460         data->args.count = 0;
461         data->res.count = 0;
462         data->res.fattr = &data->fattr;
463         data->res.verf = &data->verf;
464
465         rpc_init_task(&data->task, NFS_CLIENT(dreq->inode), RPC_TASK_ASYNC,
466                                 &nfs_commit_direct_ops, data);
467         NFS_PROTO(data->inode)->commit_setup(data, 0);
468
469         data->task.tk_priority = RPC_PRIORITY_NORMAL;
470         data->task.tk_cookie = (unsigned long)data->inode;
471         /* Note: task.tk_ops->rpc_release will free dreq->commit_data */
472         dreq->commit_data = NULL;
473
474         dprintk("NFS: %5u initiated commit call\n", data->task.tk_pid);
475
476         rpc_execute(&data->task);
477 }
478
479 static void nfs_direct_write_complete(struct nfs_direct_req *dreq, struct inode *inode)
480 {
481         int flags = dreq->flags;
482
483         dreq->flags = 0;
484         switch (flags) {
485                 case NFS_ODIRECT_DO_COMMIT:
486                         nfs_direct_commit_schedule(dreq);
487                         break;
488                 case NFS_ODIRECT_RESCHED_WRITES:
489                         nfs_direct_write_reschedule(dreq);
490                         break;
491                 default:
492                         nfs_end_data_update(inode);
493                         if (dreq->commit_data != NULL)
494                                 nfs_commit_free(dreq->commit_data);
495                         nfs_direct_free_writedata(dreq);
496                         nfs_zap_mapping(inode, inode->i_mapping);
497                         nfs_direct_complete(dreq);
498         }
499 }
500
501 static void nfs_alloc_commit_data(struct nfs_direct_req *dreq)
502 {
503         dreq->commit_data = nfs_commit_alloc();
504         if (dreq->commit_data != NULL)
505                 dreq->commit_data->req = (struct nfs_page *) dreq;
506 }
507 #else
508 static inline void nfs_alloc_commit_data(struct nfs_direct_req *dreq)
509 {
510         dreq->commit_data = NULL;
511 }
512
513 static void nfs_direct_write_complete(struct nfs_direct_req *dreq, struct inode *inode)
514 {
515         nfs_end_data_update(inode);
516         nfs_direct_free_writedata(dreq);
517         nfs_zap_mapping(inode, inode->i_mapping);
518         nfs_direct_complete(dreq);
519 }
520 #endif
521
522 static void nfs_direct_write_result(struct rpc_task *task, void *calldata)
523 {
524         struct nfs_write_data *data = calldata;
525         struct nfs_direct_req *dreq = (struct nfs_direct_req *) data->req;
526         int status = task->tk_status;
527
528         if (nfs_writeback_done(task, data) != 0)
529                 return;
530
531         spin_lock(&dreq->lock);
532
533         if (unlikely(status < 0)) {
534                 dreq->error = status;
535                 goto out_unlock;
536         }
537
538         dreq->count += data->res.count;
539
540         if (data->res.verf->committed != NFS_FILE_SYNC) {
541                 switch (dreq->flags) {
542                         case 0:
543                                 memcpy(&dreq->verf, &data->verf, sizeof(dreq->verf));
544                                 dreq->flags = NFS_ODIRECT_DO_COMMIT;
545                                 break;
546                         case NFS_ODIRECT_DO_COMMIT:
547                                 if (memcmp(&dreq->verf, &data->verf, sizeof(dreq->verf))) {
548                                         dprintk("NFS: %5u write verify failed\n", task->tk_pid);
549                                         dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
550                                 }
551                 }
552         }
553 out_unlock:
554         spin_unlock(&dreq->lock);
555 }
556
557 /*
558  * NB: Return the value of the first error return code.  Subsequent
559  *     errors after the first one are ignored.
560  */
561 static void nfs_direct_write_release(void *calldata)
562 {
563         struct nfs_write_data *data = calldata;
564         struct nfs_direct_req *dreq = (struct nfs_direct_req *) data->req;
565
566         if (put_dreq(dreq))
567                 nfs_direct_write_complete(dreq, data->inode);
568 }
569
570 static const struct rpc_call_ops nfs_write_direct_ops = {
571         .rpc_call_done = nfs_direct_write_result,
572         .rpc_release = nfs_direct_write_release,
573 };
574
575 /*
576  * For each wsize'd chunk of the user's buffer, dispatch an NFS WRITE
577  * operation.  If nfs_writedata_alloc() or get_user_pages() fails,
578  * bail and stop sending more writes.  Write length accounting is
579  * handled automatically by nfs_direct_write_result().  Otherwise, if
580  * no requests have been sent, just return an error.
581  */
582 static ssize_t nfs_direct_write_schedule(struct nfs_direct_req *dreq, unsigned long user_addr, size_t count, loff_t pos, int sync)
583 {
584         struct nfs_open_context *ctx = dreq->ctx;
585         struct inode *inode = ctx->dentry->d_inode;
586         size_t wsize = NFS_SERVER(inode)->wsize;
587         unsigned int pgbase;
588         int result;
589         ssize_t started = 0;
590
591         get_dreq(dreq);
592
593         do {
594                 struct nfs_write_data *data;
595                 size_t bytes;
596
597                 pgbase = user_addr & ~PAGE_MASK;
598                 bytes = min(wsize,count);
599
600                 result = -ENOMEM;
601                 data = nfs_writedata_alloc(pgbase + bytes);
602                 if (unlikely(!data))
603                         break;
604
605                 down_read(&current->mm->mmap_sem);
606                 result = get_user_pages(current, current->mm, user_addr,
607                                         data->npages, 0, 0, data->pagevec, NULL);
608                 up_read(&current->mm->mmap_sem);
609                 if (unlikely(result < data->npages)) {
610                         if (result > 0)
611                                 nfs_direct_release_pages(data->pagevec, result);
612                         nfs_writedata_release(data);
613                         break;
614                 }
615
616                 get_dreq(dreq);
617
618                 list_move_tail(&data->pages, &dreq->rewrite_list);
619
620                 data->req = (struct nfs_page *) dreq;
621                 data->inode = inode;
622                 data->cred = ctx->cred;
623                 data->args.fh = NFS_FH(inode);
624                 data->args.context = ctx;
625                 data->args.offset = pos;
626                 data->args.pgbase = pgbase;
627                 data->args.pages = data->pagevec;
628                 data->args.count = bytes;
629                 data->res.fattr = &data->fattr;
630                 data->res.count = bytes;
631                 data->res.verf = &data->verf;
632
633                 rpc_init_task(&data->task, NFS_CLIENT(inode), RPC_TASK_ASYNC,
634                                 &nfs_write_direct_ops, data);
635                 NFS_PROTO(inode)->write_setup(data, sync);
636
637                 data->task.tk_priority = RPC_PRIORITY_NORMAL;
638                 data->task.tk_cookie = (unsigned long) inode;
639
640                 rpc_execute(&data->task);
641
642                 dfprintk(VFS, "NFS: %5u initiated direct write call (req %s/%Ld, %zu bytes @ offset %Lu)\n",
643                                 data->task.tk_pid,
644                                 inode->i_sb->s_id,
645                                 (long long)NFS_FILEID(inode),
646                                 bytes,
647                                 (unsigned long long)data->args.offset);
648
649                 started += bytes;
650                 user_addr += bytes;
651                 pos += bytes;
652
653                 /* FIXME: Remove this useless math from the final patch */
654                 pgbase += bytes;
655                 pgbase &= ~PAGE_MASK;
656                 BUG_ON(pgbase != (user_addr & ~PAGE_MASK));
657
658                 count -= bytes;
659         } while (count != 0);
660
661         if (put_dreq(dreq))
662                 nfs_direct_write_complete(dreq, inode);
663
664         if (started)
665                 return 0;
666         return result < 0 ? (ssize_t) result : -EFAULT;
667 }
668
669 static ssize_t nfs_direct_write(struct kiocb *iocb, unsigned long user_addr, size_t count, loff_t pos)
670 {
671         ssize_t result = 0;
672         sigset_t oldset;
673         struct inode *inode = iocb->ki_filp->f_mapping->host;
674         struct rpc_clnt *clnt = NFS_CLIENT(inode);
675         struct nfs_direct_req *dreq;
676         size_t wsize = NFS_SERVER(inode)->wsize;
677         int sync = 0;
678
679         dreq = nfs_direct_req_alloc();
680         if (!dreq)
681                 return -ENOMEM;
682         nfs_alloc_commit_data(dreq);
683
684         if (dreq->commit_data == NULL || count < wsize)
685                 sync = FLUSH_STABLE;
686
687         dreq->inode = inode;
688         dreq->ctx = get_nfs_open_context((struct nfs_open_context *)iocb->ki_filp->private_data);
689         if (!is_sync_kiocb(iocb))
690                 dreq->iocb = iocb;
691
692         nfs_add_stats(inode, NFSIOS_DIRECTWRITTENBYTES, count);
693
694         nfs_begin_data_update(inode);
695
696         rpc_clnt_sigmask(clnt, &oldset);
697         result = nfs_direct_write_schedule(dreq, user_addr, count, pos, sync);
698         if (!result)
699                 result = nfs_direct_wait(dreq);
700         rpc_clnt_sigunmask(clnt, &oldset);
701
702         return result;
703 }
704
705 /**
706  * nfs_file_direct_read - file direct read operation for NFS files
707  * @iocb: target I/O control block
708  * @iov: vector of user buffers into which to read data
709  * @nr_segs: size of iov vector
710  * @pos: byte offset in file where reading starts
711  *
712  * We use this function for direct reads instead of calling
713  * generic_file_aio_read() in order to avoid gfar's check to see if
714  * the request starts before the end of the file.  For that check
715  * to work, we must generate a GETATTR before each direct read, and
716  * even then there is a window between the GETATTR and the subsequent
717  * READ where the file size could change.  Our preference is simply
718  * to do all reads the application wants, and the server will take
719  * care of managing the end of file boundary.
720  *
721  * This function also eliminates unnecessarily updating the file's
722  * atime locally, as the NFS server sets the file's atime, and this
723  * client must read the updated atime from the server back into its
724  * cache.
725  */
726 ssize_t nfs_file_direct_read(struct kiocb *iocb, const struct iovec *iov,
727                                 unsigned long nr_segs, loff_t pos)
728 {
729         ssize_t retval = -EINVAL;
730         struct file *file = iocb->ki_filp;
731         struct address_space *mapping = file->f_mapping;
732         /* XXX: temporary */
733         const char __user *buf = iov[0].iov_base;
734         size_t count = iov[0].iov_len;
735
736         dprintk("nfs: direct read(%s/%s, %lu@%Ld)\n",
737                 file->f_dentry->d_parent->d_name.name,
738                 file->f_dentry->d_name.name,
739                 (unsigned long) count, (long long) pos);
740
741         if (nr_segs != 1)
742                 return -EINVAL;
743
744         if (count < 0)
745                 goto out;
746         retval = -EFAULT;
747         if (!access_ok(VERIFY_WRITE, buf, count))
748                 goto out;
749         retval = 0;
750         if (!count)
751                 goto out;
752
753         retval = nfs_sync_mapping(mapping);
754         if (retval)
755                 goto out;
756
757         retval = nfs_direct_read(iocb, (unsigned long) buf, count, pos);
758         if (retval > 0)
759                 iocb->ki_pos = pos + retval;
760
761 out:
762         return retval;
763 }
764
765 /**
766  * nfs_file_direct_write - file direct write operation for NFS files
767  * @iocb: target I/O control block
768  * @iov: vector of user buffers from which to write data
769  * @nr_segs: size of iov vector
770  * @pos: byte offset in file where writing starts
771  *
772  * We use this function for direct writes instead of calling
773  * generic_file_aio_write() in order to avoid taking the inode
774  * semaphore and updating the i_size.  The NFS server will set
775  * the new i_size and this client must read the updated size
776  * back into its cache.  We let the server do generic write
777  * parameter checking and report problems.
778  *
779  * We also avoid an unnecessary invocation of generic_osync_inode(),
780  * as it is fairly meaningless to sync the metadata of an NFS file.
781  *
782  * We eliminate local atime updates, see direct read above.
783  *
784  * We avoid unnecessary page cache invalidations for normal cached
785  * readers of this file.
786  *
787  * Note that O_APPEND is not supported for NFS direct writes, as there
788  * is no atomic O_APPEND write facility in the NFS protocol.
789  */
790 ssize_t nfs_file_direct_write(struct kiocb *iocb, const struct iovec *iov,
791                                 unsigned long nr_segs, loff_t pos)
792 {
793         ssize_t retval;
794         struct file *file = iocb->ki_filp;
795         struct address_space *mapping = file->f_mapping;
796         /* XXX: temporary */
797         const char __user *buf = iov[0].iov_base;
798         size_t count = iov[0].iov_len;
799
800         dfprintk(VFS, "nfs: direct write(%s/%s, %lu@%Ld)\n",
801                 file->f_dentry->d_parent->d_name.name,
802                 file->f_dentry->d_name.name,
803                 (unsigned long) count, (long long) pos);
804
805         if (nr_segs != 1)
806                 return -EINVAL;
807
808         retval = generic_write_checks(file, &pos, &count, 0);
809         if (retval)
810                 goto out;
811
812         retval = -EINVAL;
813         if ((ssize_t) count < 0)
814                 goto out;
815         retval = 0;
816         if (!count)
817                 goto out;
818
819         retval = -EFAULT;
820         if (!access_ok(VERIFY_READ, buf, count))
821                 goto out;
822
823         retval = nfs_sync_mapping(mapping);
824         if (retval)
825                 goto out;
826
827         retval = nfs_direct_write(iocb, (unsigned long) buf, count, pos);
828
829         if (retval > 0)
830                 iocb->ki_pos = pos + retval;
831
832 out:
833         return retval;
834 }
835
836 /**
837  * nfs_init_directcache - create a slab cache for nfs_direct_req structures
838  *
839  */
840 int __init nfs_init_directcache(void)
841 {
842         nfs_direct_cachep = kmem_cache_create("nfs_direct_cache",
843                                                 sizeof(struct nfs_direct_req),
844                                                 0, (SLAB_RECLAIM_ACCOUNT|
845                                                         SLAB_MEM_SPREAD),
846                                                 NULL, NULL);
847         if (nfs_direct_cachep == NULL)
848                 return -ENOMEM;
849
850         return 0;
851 }
852
853 /**
854  * nfs_destroy_directcache - destroy the slab cache for nfs_direct_req structures
855  *
856  */
857 void nfs_destroy_directcache(void)
858 {
859         kmem_cache_destroy(nfs_direct_cachep);
860 }