2 * linux/fs/nfs/direct.c
4 * Copyright (C) 2003 by Chuck Lever <cel@netapp.com>
6 * High-performance uncached I/O for the Linux NFS client
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.
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
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.
29 * Designed by Jeff Kimmel, Chuck Lever, and Trond Myklebust, with
30 * help from Andrew Morton.
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
41 #include <linux/errno.h>
42 #include <linux/sched.h>
43 #include <linux/kernel.h>
44 #include <linux/file.h>
45 #include <linux/pagemap.h>
46 #include <linux/kref.h>
48 #include <linux/nfs_fs.h>
49 #include <linux/nfs_page.h>
50 #include <linux/sunrpc/clnt.h>
52 #include <asm/system.h>
53 #include <asm/uaccess.h>
54 #include <asm/atomic.h>
59 #define NFSDBG_FACILITY NFSDBG_VFS
61 static struct kmem_cache
*nfs_direct_cachep
;
64 * This represents a set of asynchronous requests that we're waiting on
66 struct nfs_direct_req
{
67 struct kref kref
; /* release manager */
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 */
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 */
82 struct list_head rewrite_list
; /* saved nfs_write_data structs */
83 struct nfs_write_data
* commit_data
; /* special write_data for commits */
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 */
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
;
93 static inline void get_dreq(struct nfs_direct_req
*dreq
)
95 atomic_inc(&dreq
->io_count
);
98 static inline int put_dreq(struct nfs_direct_req
*dreq
)
100 return atomic_dec_and_test(&dreq
->io_count
);
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
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.
116 ssize_t
nfs_direct_IO(int rw
, struct kiocb
*iocb
, const struct iovec
*iov
, loff_t pos
, unsigned long nr_segs
)
118 dprintk("NFS: nfs_direct_IO (%s) off/no(%Ld/%lu) EINVAL\n",
119 iocb
->ki_filp
->f_path
.dentry
->d_name
.name
,
120 (long long) pos
, nr_segs
);
125 static void nfs_direct_dirty_pages(struct page
**pages
, unsigned int pgbase
, size_t count
)
132 pages
+= (pgbase
>> PAGE_SHIFT
);
133 npages
= (count
+ (pgbase
& ~PAGE_MASK
) + PAGE_SIZE
- 1) >> PAGE_SHIFT
;
134 for (i
= 0; i
< npages
; i
++) {
135 struct page
*page
= pages
[i
];
136 if (!PageCompound(page
))
137 set_page_dirty(page
);
141 static void nfs_direct_release_pages(struct page
**pages
, unsigned int npages
)
144 for (i
= 0; i
< npages
; i
++)
145 page_cache_release(pages
[i
]);
148 static inline struct nfs_direct_req
*nfs_direct_req_alloc(void)
150 struct nfs_direct_req
*dreq
;
152 dreq
= kmem_cache_alloc(nfs_direct_cachep
, GFP_KERNEL
);
156 kref_init(&dreq
->kref
);
157 kref_get(&dreq
->kref
);
158 init_completion(&dreq
->completion
);
159 INIT_LIST_HEAD(&dreq
->rewrite_list
);
162 spin_lock_init(&dreq
->lock
);
163 atomic_set(&dreq
->io_count
, 0);
171 static void nfs_direct_req_free(struct kref
*kref
)
173 struct nfs_direct_req
*dreq
= container_of(kref
, struct nfs_direct_req
, kref
);
175 if (dreq
->ctx
!= NULL
)
176 put_nfs_open_context(dreq
->ctx
);
177 kmem_cache_free(nfs_direct_cachep
, dreq
);
180 static void nfs_direct_req_release(struct nfs_direct_req
*dreq
)
182 kref_put(&dreq
->kref
, nfs_direct_req_free
);
186 * Collects and returns the final error value/byte-count.
188 static ssize_t
nfs_direct_wait(struct nfs_direct_req
*dreq
)
190 ssize_t result
= -EIOCBQUEUED
;
192 /* Async requests don't wait here */
196 result
= wait_for_completion_interruptible(&dreq
->completion
);
199 result
= dreq
->error
;
201 result
= dreq
->count
;
204 return (ssize_t
) result
;
208 * Synchronous I/O uses a stack-allocated iocb. Thus we can't trust
209 * the iocb is still valid here if this is a synchronous request.
211 static void nfs_direct_complete(struct nfs_direct_req
*dreq
)
214 long res
= (long) dreq
->error
;
216 res
= (long) dreq
->count
;
217 aio_complete(dreq
->iocb
, res
, 0);
219 complete_all(&dreq
->completion
);
221 nfs_direct_req_release(dreq
);
225 * We must hold a reference to all the pages in this direct read request
226 * until the RPCs complete. This could be long *after* we are woken up in
227 * nfs_direct_wait (for instance, if someone hits ^C on a slow server).
229 static void nfs_direct_read_result(struct rpc_task
*task
, void *calldata
)
231 struct nfs_read_data
*data
= calldata
;
232 struct nfs_direct_req
*dreq
= (struct nfs_direct_req
*) data
->req
;
234 if (nfs_readpage_result(task
, data
) != 0)
237 spin_lock(&dreq
->lock
);
238 if (unlikely(task
->tk_status
< 0)) {
239 dreq
->error
= task
->tk_status
;
240 spin_unlock(&dreq
->lock
);
242 dreq
->count
+= data
->res
.count
;
243 spin_unlock(&dreq
->lock
);
244 nfs_direct_dirty_pages(data
->pagevec
,
248 nfs_direct_release_pages(data
->pagevec
, data
->npages
);
251 nfs_direct_complete(dreq
);
254 static const struct rpc_call_ops nfs_read_direct_ops
= {
255 .rpc_call_done
= nfs_direct_read_result
,
256 .rpc_release
= nfs_readdata_release
,
260 * For each rsize'd chunk of the user's buffer, dispatch an NFS READ
261 * operation. If nfs_readdata_alloc() or get_user_pages() fails,
262 * bail and stop sending more reads. Read length accounting is
263 * handled automatically by nfs_direct_read_result(). Otherwise, if
264 * no requests have been sent, just return an error.
266 static ssize_t
nfs_direct_read_schedule(struct nfs_direct_req
*dreq
, unsigned long user_addr
, size_t count
, loff_t pos
)
268 struct nfs_open_context
*ctx
= dreq
->ctx
;
269 struct inode
*inode
= ctx
->path
.dentry
->d_inode
;
270 size_t rsize
= NFS_SERVER(inode
)->rsize
;
278 struct nfs_read_data
*data
;
281 pgbase
= user_addr
& ~PAGE_MASK
;
282 bytes
= min(rsize
,count
);
285 data
= nfs_readdata_alloc(nfs_page_array_len(pgbase
, bytes
));
289 down_read(¤t
->mm
->mmap_sem
);
290 result
= get_user_pages(current
, current
->mm
, user_addr
,
291 data
->npages
, 1, 0, data
->pagevec
, NULL
);
292 up_read(¤t
->mm
->mmap_sem
);
294 nfs_readdata_release(data
);
297 if ((unsigned)result
< data
->npages
) {
298 bytes
= result
* PAGE_SIZE
;
299 if (bytes
<= pgbase
) {
300 nfs_direct_release_pages(data
->pagevec
, result
);
301 nfs_readdata_release(data
);
305 data
->npages
= result
;
310 data
->req
= (struct nfs_page
*) dreq
;
312 data
->cred
= ctx
->cred
;
313 data
->args
.fh
= NFS_FH(inode
);
314 data
->args
.context
= ctx
;
315 data
->args
.offset
= pos
;
316 data
->args
.pgbase
= pgbase
;
317 data
->args
.pages
= data
->pagevec
;
318 data
->args
.count
= bytes
;
319 data
->res
.fattr
= &data
->fattr
;
321 data
->res
.count
= bytes
;
323 rpc_init_task(&data
->task
, NFS_CLIENT(inode
), RPC_TASK_ASYNC
,
324 &nfs_read_direct_ops
, data
);
325 NFS_PROTO(inode
)->read_setup(data
);
327 data
->task
.tk_cookie
= (unsigned long) inode
;
329 rpc_execute(&data
->task
);
331 dprintk("NFS: %5u initiated direct read call "
332 "(req %s/%Ld, %zu bytes @ offset %Lu)\n",
335 (long long)NFS_FILEID(inode
),
337 (unsigned long long)data
->args
.offset
);
342 /* FIXME: Remove this unnecessary math from final patch */
344 pgbase
&= ~PAGE_MASK
;
345 BUG_ON(pgbase
!= (user_addr
& ~PAGE_MASK
));
348 } while (count
!= 0);
351 nfs_direct_complete(dreq
);
355 return result
< 0 ? (ssize_t
) result
: -EFAULT
;
358 static ssize_t
nfs_direct_read(struct kiocb
*iocb
, unsigned long user_addr
, size_t count
, loff_t pos
)
362 struct inode
*inode
= iocb
->ki_filp
->f_mapping
->host
;
363 struct rpc_clnt
*clnt
= NFS_CLIENT(inode
);
364 struct nfs_direct_req
*dreq
;
366 dreq
= nfs_direct_req_alloc();
371 dreq
->ctx
= get_nfs_open_context((struct nfs_open_context
*)iocb
->ki_filp
->private_data
);
372 if (!is_sync_kiocb(iocb
))
375 nfs_add_stats(inode
, NFSIOS_DIRECTREADBYTES
, count
);
376 rpc_clnt_sigmask(clnt
, &oldset
);
377 result
= nfs_direct_read_schedule(dreq
, user_addr
, count
, pos
);
379 result
= nfs_direct_wait(dreq
);
380 rpc_clnt_sigunmask(clnt
, &oldset
);
381 nfs_direct_req_release(dreq
);
386 static void nfs_direct_free_writedata(struct nfs_direct_req
*dreq
)
388 while (!list_empty(&dreq
->rewrite_list
)) {
389 struct nfs_write_data
*data
= list_entry(dreq
->rewrite_list
.next
, struct nfs_write_data
, pages
);
390 list_del(&data
->pages
);
391 nfs_direct_release_pages(data
->pagevec
, data
->npages
);
392 nfs_writedata_release(data
);
396 #if defined(CONFIG_NFS_V3) || defined(CONFIG_NFS_V4)
397 static void nfs_direct_write_reschedule(struct nfs_direct_req
*dreq
)
399 struct inode
*inode
= dreq
->inode
;
401 struct nfs_write_data
*data
;
406 list_for_each(p
, &dreq
->rewrite_list
) {
407 data
= list_entry(p
, struct nfs_write_data
, pages
);
414 nfs_fattr_init(&data
->fattr
);
415 data
->res
.count
= data
->args
.count
;
416 memset(&data
->verf
, 0, sizeof(data
->verf
));
419 * Reuse data->task; data->args should not have changed
420 * since the original request was sent.
422 rpc_init_task(&data
->task
, NFS_CLIENT(inode
), RPC_TASK_ASYNC
,
423 &nfs_write_direct_ops
, data
);
424 NFS_PROTO(inode
)->write_setup(data
, FLUSH_STABLE
);
426 data
->task
.tk_priority
= RPC_PRIORITY_NORMAL
;
427 data
->task
.tk_cookie
= (unsigned long) inode
;
430 * We're called via an RPC callback, so BKL is already held.
432 rpc_execute(&data
->task
);
434 dprintk("NFS: %5u rescheduled direct write call (req %s/%Ld, %u bytes @ offset %Lu)\n",
437 (long long)NFS_FILEID(inode
),
439 (unsigned long long)data
->args
.offset
);
443 nfs_direct_write_complete(dreq
, inode
);
446 static void nfs_direct_commit_result(struct rpc_task
*task
, void *calldata
)
448 struct nfs_write_data
*data
= calldata
;
449 struct nfs_direct_req
*dreq
= (struct nfs_direct_req
*) data
->req
;
451 /* Call the NFS version-specific code */
452 if (NFS_PROTO(data
->inode
)->commit_done(task
, data
) != 0)
454 if (unlikely(task
->tk_status
< 0)) {
455 dprintk("NFS: %5u commit failed with error %d.\n",
456 task
->tk_pid
, task
->tk_status
);
457 dreq
->flags
= NFS_ODIRECT_RESCHED_WRITES
;
458 } else if (memcmp(&dreq
->verf
, &data
->verf
, sizeof(data
->verf
))) {
459 dprintk("NFS: %5u commit verify failed\n", task
->tk_pid
);
460 dreq
->flags
= NFS_ODIRECT_RESCHED_WRITES
;
463 dprintk("NFS: %5u commit returned %d\n", task
->tk_pid
, task
->tk_status
);
464 nfs_direct_write_complete(dreq
, data
->inode
);
467 static const struct rpc_call_ops nfs_commit_direct_ops
= {
468 .rpc_call_done
= nfs_direct_commit_result
,
469 .rpc_release
= nfs_commit_release
,
472 static void nfs_direct_commit_schedule(struct nfs_direct_req
*dreq
)
474 struct nfs_write_data
*data
= dreq
->commit_data
;
476 data
->inode
= dreq
->inode
;
477 data
->cred
= dreq
->ctx
->cred
;
479 data
->args
.fh
= NFS_FH(data
->inode
);
480 data
->args
.offset
= 0;
481 data
->args
.count
= 0;
483 data
->res
.fattr
= &data
->fattr
;
484 data
->res
.verf
= &data
->verf
;
486 rpc_init_task(&data
->task
, NFS_CLIENT(dreq
->inode
), RPC_TASK_ASYNC
,
487 &nfs_commit_direct_ops
, data
);
488 NFS_PROTO(data
->inode
)->commit_setup(data
, 0);
490 data
->task
.tk_priority
= RPC_PRIORITY_NORMAL
;
491 data
->task
.tk_cookie
= (unsigned long)data
->inode
;
492 /* Note: task.tk_ops->rpc_release will free dreq->commit_data */
493 dreq
->commit_data
= NULL
;
495 dprintk("NFS: %5u initiated commit call\n", data
->task
.tk_pid
);
497 rpc_execute(&data
->task
);
500 static void nfs_direct_write_complete(struct nfs_direct_req
*dreq
, struct inode
*inode
)
502 int flags
= dreq
->flags
;
506 case NFS_ODIRECT_DO_COMMIT
:
507 nfs_direct_commit_schedule(dreq
);
509 case NFS_ODIRECT_RESCHED_WRITES
:
510 nfs_direct_write_reschedule(dreq
);
513 nfs_end_data_update(inode
);
514 if (dreq
->commit_data
!= NULL
)
515 nfs_commit_free(dreq
->commit_data
);
516 nfs_direct_free_writedata(dreq
);
517 nfs_zap_mapping(inode
, inode
->i_mapping
);
518 nfs_direct_complete(dreq
);
522 static void nfs_alloc_commit_data(struct nfs_direct_req
*dreq
)
524 dreq
->commit_data
= nfs_commit_alloc();
525 if (dreq
->commit_data
!= NULL
)
526 dreq
->commit_data
->req
= (struct nfs_page
*) dreq
;
529 static inline void nfs_alloc_commit_data(struct nfs_direct_req
*dreq
)
531 dreq
->commit_data
= NULL
;
534 static void nfs_direct_write_complete(struct nfs_direct_req
*dreq
, struct inode
*inode
)
536 nfs_end_data_update(inode
);
537 nfs_direct_free_writedata(dreq
);
538 nfs_zap_mapping(inode
, inode
->i_mapping
);
539 nfs_direct_complete(dreq
);
543 static void nfs_direct_write_result(struct rpc_task
*task
, void *calldata
)
545 struct nfs_write_data
*data
= calldata
;
546 struct nfs_direct_req
*dreq
= (struct nfs_direct_req
*) data
->req
;
547 int status
= task
->tk_status
;
549 if (nfs_writeback_done(task
, data
) != 0)
552 spin_lock(&dreq
->lock
);
554 if (unlikely(dreq
->error
!= 0))
556 if (unlikely(status
< 0)) {
557 /* An error has occured, so we should not commit */
559 dreq
->error
= status
;
562 dreq
->count
+= data
->res
.count
;
564 if (data
->res
.verf
->committed
!= NFS_FILE_SYNC
) {
565 switch (dreq
->flags
) {
567 memcpy(&dreq
->verf
, &data
->verf
, sizeof(dreq
->verf
));
568 dreq
->flags
= NFS_ODIRECT_DO_COMMIT
;
570 case NFS_ODIRECT_DO_COMMIT
:
571 if (memcmp(&dreq
->verf
, &data
->verf
, sizeof(dreq
->verf
))) {
572 dprintk("NFS: %5u write verify failed\n", task
->tk_pid
);
573 dreq
->flags
= NFS_ODIRECT_RESCHED_WRITES
;
578 spin_unlock(&dreq
->lock
);
582 * NB: Return the value of the first error return code. Subsequent
583 * errors after the first one are ignored.
585 static void nfs_direct_write_release(void *calldata
)
587 struct nfs_write_data
*data
= calldata
;
588 struct nfs_direct_req
*dreq
= (struct nfs_direct_req
*) data
->req
;
591 nfs_direct_write_complete(dreq
, data
->inode
);
594 static const struct rpc_call_ops nfs_write_direct_ops
= {
595 .rpc_call_done
= nfs_direct_write_result
,
596 .rpc_release
= nfs_direct_write_release
,
600 * For each wsize'd chunk of the user's buffer, dispatch an NFS WRITE
601 * operation. If nfs_writedata_alloc() or get_user_pages() fails,
602 * bail and stop sending more writes. Write length accounting is
603 * handled automatically by nfs_direct_write_result(). Otherwise, if
604 * no requests have been sent, just return an error.
606 static ssize_t
nfs_direct_write_schedule(struct nfs_direct_req
*dreq
, unsigned long user_addr
, size_t count
, loff_t pos
, int sync
)
608 struct nfs_open_context
*ctx
= dreq
->ctx
;
609 struct inode
*inode
= ctx
->path
.dentry
->d_inode
;
610 size_t wsize
= NFS_SERVER(inode
)->wsize
;
618 struct nfs_write_data
*data
;
621 pgbase
= user_addr
& ~PAGE_MASK
;
622 bytes
= min(wsize
,count
);
625 data
= nfs_writedata_alloc(nfs_page_array_len(pgbase
, bytes
));
629 down_read(¤t
->mm
->mmap_sem
);
630 result
= get_user_pages(current
, current
->mm
, user_addr
,
631 data
->npages
, 0, 0, data
->pagevec
, NULL
);
632 up_read(¤t
->mm
->mmap_sem
);
634 nfs_writedata_release(data
);
637 if ((unsigned)result
< data
->npages
) {
638 bytes
= result
* PAGE_SIZE
;
639 if (bytes
<= pgbase
) {
640 nfs_direct_release_pages(data
->pagevec
, result
);
641 nfs_writedata_release(data
);
645 data
->npages
= result
;
650 list_move_tail(&data
->pages
, &dreq
->rewrite_list
);
652 data
->req
= (struct nfs_page
*) dreq
;
654 data
->cred
= ctx
->cred
;
655 data
->args
.fh
= NFS_FH(inode
);
656 data
->args
.context
= ctx
;
657 data
->args
.offset
= pos
;
658 data
->args
.pgbase
= pgbase
;
659 data
->args
.pages
= data
->pagevec
;
660 data
->args
.count
= bytes
;
661 data
->res
.fattr
= &data
->fattr
;
662 data
->res
.count
= bytes
;
663 data
->res
.verf
= &data
->verf
;
665 rpc_init_task(&data
->task
, NFS_CLIENT(inode
), RPC_TASK_ASYNC
,
666 &nfs_write_direct_ops
, data
);
667 NFS_PROTO(inode
)->write_setup(data
, sync
);
669 data
->task
.tk_priority
= RPC_PRIORITY_NORMAL
;
670 data
->task
.tk_cookie
= (unsigned long) inode
;
672 rpc_execute(&data
->task
);
674 dprintk("NFS: %5u initiated direct write call "
675 "(req %s/%Ld, %zu bytes @ offset %Lu)\n",
678 (long long)NFS_FILEID(inode
),
680 (unsigned long long)data
->args
.offset
);
686 /* FIXME: Remove this useless math from the final patch */
688 pgbase
&= ~PAGE_MASK
;
689 BUG_ON(pgbase
!= (user_addr
& ~PAGE_MASK
));
692 } while (count
!= 0);
695 nfs_direct_write_complete(dreq
, inode
);
699 return result
< 0 ? (ssize_t
) result
: -EFAULT
;
702 static ssize_t
nfs_direct_write(struct kiocb
*iocb
, unsigned long user_addr
, size_t count
, loff_t pos
)
706 struct inode
*inode
= iocb
->ki_filp
->f_mapping
->host
;
707 struct rpc_clnt
*clnt
= NFS_CLIENT(inode
);
708 struct nfs_direct_req
*dreq
;
709 size_t wsize
= NFS_SERVER(inode
)->wsize
;
712 dreq
= nfs_direct_req_alloc();
715 nfs_alloc_commit_data(dreq
);
717 if (dreq
->commit_data
== NULL
|| count
< wsize
)
721 dreq
->ctx
= get_nfs_open_context((struct nfs_open_context
*)iocb
->ki_filp
->private_data
);
722 if (!is_sync_kiocb(iocb
))
725 nfs_add_stats(inode
, NFSIOS_DIRECTWRITTENBYTES
, count
);
727 nfs_begin_data_update(inode
);
729 rpc_clnt_sigmask(clnt
, &oldset
);
730 result
= nfs_direct_write_schedule(dreq
, user_addr
, count
, pos
, sync
);
732 result
= nfs_direct_wait(dreq
);
733 rpc_clnt_sigunmask(clnt
, &oldset
);
734 nfs_direct_req_release(dreq
);
740 * nfs_file_direct_read - file direct read operation for NFS files
741 * @iocb: target I/O control block
742 * @iov: vector of user buffers into which to read data
743 * @nr_segs: size of iov vector
744 * @pos: byte offset in file where reading starts
746 * We use this function for direct reads instead of calling
747 * generic_file_aio_read() in order to avoid gfar's check to see if
748 * the request starts before the end of the file. For that check
749 * to work, we must generate a GETATTR before each direct read, and
750 * even then there is a window between the GETATTR and the subsequent
751 * READ where the file size could change. Our preference is simply
752 * to do all reads the application wants, and the server will take
753 * care of managing the end of file boundary.
755 * This function also eliminates unnecessarily updating the file's
756 * atime locally, as the NFS server sets the file's atime, and this
757 * client must read the updated atime from the server back into its
760 ssize_t
nfs_file_direct_read(struct kiocb
*iocb
, const struct iovec
*iov
,
761 unsigned long nr_segs
, loff_t pos
)
763 ssize_t retval
= -EINVAL
;
764 struct file
*file
= iocb
->ki_filp
;
765 struct address_space
*mapping
= file
->f_mapping
;
767 const char __user
*buf
= iov
[0].iov_base
;
768 size_t count
= iov
[0].iov_len
;
770 dprintk("nfs: direct read(%s/%s, %lu@%Ld)\n",
771 file
->f_path
.dentry
->d_parent
->d_name
.name
,
772 file
->f_path
.dentry
->d_name
.name
,
773 (unsigned long) count
, (long long) pos
);
779 if (!access_ok(VERIFY_WRITE
, buf
, count
))
785 retval
= nfs_sync_mapping(mapping
);
789 retval
= nfs_direct_read(iocb
, (unsigned long) buf
, count
, pos
);
791 iocb
->ki_pos
= pos
+ retval
;
798 * nfs_file_direct_write - file direct write operation for NFS files
799 * @iocb: target I/O control block
800 * @iov: vector of user buffers from which to write data
801 * @nr_segs: size of iov vector
802 * @pos: byte offset in file where writing starts
804 * We use this function for direct writes instead of calling
805 * generic_file_aio_write() in order to avoid taking the inode
806 * semaphore and updating the i_size. The NFS server will set
807 * the new i_size and this client must read the updated size
808 * back into its cache. We let the server do generic write
809 * parameter checking and report problems.
811 * We also avoid an unnecessary invocation of generic_osync_inode(),
812 * as it is fairly meaningless to sync the metadata of an NFS file.
814 * We eliminate local atime updates, see direct read above.
816 * We avoid unnecessary page cache invalidations for normal cached
817 * readers of this file.
819 * Note that O_APPEND is not supported for NFS direct writes, as there
820 * is no atomic O_APPEND write facility in the NFS protocol.
822 ssize_t
nfs_file_direct_write(struct kiocb
*iocb
, const struct iovec
*iov
,
823 unsigned long nr_segs
, loff_t pos
)
825 ssize_t retval
= -EINVAL
;
826 struct file
*file
= iocb
->ki_filp
;
827 struct address_space
*mapping
= file
->f_mapping
;
829 const char __user
*buf
= iov
[0].iov_base
;
830 size_t count
= iov
[0].iov_len
;
832 dprintk("nfs: direct write(%s/%s, %lu@%Ld)\n",
833 file
->f_path
.dentry
->d_parent
->d_name
.name
,
834 file
->f_path
.dentry
->d_name
.name
,
835 (unsigned long) count
, (long long) pos
);
840 retval
= generic_write_checks(file
, &pos
, &count
, 0);
845 if ((ssize_t
) count
< 0)
852 if (!access_ok(VERIFY_READ
, buf
, count
))
855 retval
= nfs_sync_mapping(mapping
);
859 retval
= nfs_direct_write(iocb
, (unsigned long) buf
, count
, pos
);
862 iocb
->ki_pos
= pos
+ retval
;
869 * nfs_init_directcache - create a slab cache for nfs_direct_req structures
872 int __init
nfs_init_directcache(void)
874 nfs_direct_cachep
= kmem_cache_create("nfs_direct_cache",
875 sizeof(struct nfs_direct_req
),
876 0, (SLAB_RECLAIM_ACCOUNT
|
879 if (nfs_direct_cachep
== NULL
)
886 * nfs_destroy_directcache - destroy the slab cache for nfs_direct_req structures
889 void nfs_destroy_directcache(void)
891 kmem_cache_destroy(nfs_direct_cachep
);