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>
47 #include <linux/slab.h>
48 #include <linux/task_io_accounting_ops.h>
49 #include <linux/module.h>
51 #include <linux/nfs_fs.h>
52 #include <linux/nfs_page.h>
53 #include <linux/sunrpc/clnt.h>
55 #include <asm/uaccess.h>
56 #include <linux/atomic.h>
62 #define NFSDBG_FACILITY NFSDBG_VFS
64 static struct kmem_cache *nfs_direct_cachep;
67 * This represents a set of asynchronous requests that we're waiting on
69 struct nfs_direct_req {
70 struct kref kref; /* release manager */
73 struct nfs_open_context *ctx; /* file open context info */
74 struct nfs_lock_context *l_ctx; /* Lock context info */
75 struct kiocb * iocb; /* controlling i/o request */
76 struct inode * inode; /* target file of i/o */
78 /* completion state */
79 atomic_t io_count; /* i/os we're waiting for */
80 spinlock_t lock; /* protect completion state */
81 ssize_t count, /* bytes actually processed */
82 bytes_left, /* bytes left to be sent */
83 error; /* any reported error */
84 struct completion completion; /* wait for i/o completion */
87 struct nfs_mds_commit_info mds_cinfo; /* Storage for cinfo */
88 struct pnfs_ds_commit_info ds_cinfo; /* Storage for cinfo */
89 struct work_struct work;
91 #define NFS_ODIRECT_DO_COMMIT (1) /* an unstable reply was received */
92 #define NFS_ODIRECT_RESCHED_WRITES (2) /* write verification failed */
93 struct nfs_writeverf verf; /* unstable write verifier */
96 static const struct nfs_pgio_completion_ops nfs_direct_write_completion_ops;
97 static const struct nfs_commit_completion_ops nfs_direct_commit_completion_ops;
98 static void nfs_direct_write_complete(struct nfs_direct_req *dreq, struct inode *inode);
99 static void nfs_direct_write_schedule_work(struct work_struct *work);
101 static inline void get_dreq(struct nfs_direct_req *dreq)
103 atomic_inc(&dreq->io_count);
106 static inline int put_dreq(struct nfs_direct_req *dreq)
108 return atomic_dec_and_test(&dreq->io_count);
112 * nfs_direct_IO - NFS address space operation for direct I/O
113 * @rw: direction (read or write)
114 * @iocb: target I/O control block
115 * @iov: array of vectors that define I/O buffer
116 * @pos: offset in file to begin the operation
117 * @nr_segs: size of iovec array
119 * The presence of this routine in the address space ops vector means
120 * the NFS client supports direct I/O. However, for most direct IO, we
121 * shunt off direct read and write requests before the VFS gets them,
122 * so this method is only ever called for swap.
124 ssize_t nfs_direct_IO(int rw, struct kiocb *iocb, struct iov_iter *iter, loff_t pos)
126 #ifndef CONFIG_NFS_SWAP
127 dprintk("NFS: nfs_direct_IO (%pD) off/no(%Ld/%lu) EINVAL\n",
128 iocb->ki_filp, (long long) pos, iter->nr_segs);
132 VM_BUG_ON(iocb->ki_nbytes != PAGE_SIZE);
134 if (rw == READ || rw == KERNEL_READ)
135 return nfs_file_direct_read(iocb, iter, pos,
136 rw == READ ? true : false);
137 return nfs_file_direct_write(iocb, iter, pos,
138 rw == WRITE ? true : false);
139 #endif /* CONFIG_NFS_SWAP */
142 static void nfs_direct_release_pages(struct page **pages, unsigned int npages)
145 for (i = 0; i < npages; i++)
146 page_cache_release(pages[i]);
149 void nfs_init_cinfo_from_dreq(struct nfs_commit_info *cinfo,
150 struct nfs_direct_req *dreq)
152 cinfo->lock = &dreq->lock;
153 cinfo->mds = &dreq->mds_cinfo;
154 cinfo->ds = &dreq->ds_cinfo;
156 cinfo->completion_ops = &nfs_direct_commit_completion_ops;
159 static inline struct nfs_direct_req *nfs_direct_req_alloc(void)
161 struct nfs_direct_req *dreq;
163 dreq = kmem_cache_zalloc(nfs_direct_cachep, GFP_KERNEL);
167 kref_init(&dreq->kref);
168 kref_get(&dreq->kref);
169 init_completion(&dreq->completion);
170 INIT_LIST_HEAD(&dreq->mds_cinfo.list);
171 INIT_WORK(&dreq->work, nfs_direct_write_schedule_work);
172 spin_lock_init(&dreq->lock);
177 static void nfs_direct_req_free(struct kref *kref)
179 struct nfs_direct_req *dreq = container_of(kref, struct nfs_direct_req, kref);
181 if (dreq->l_ctx != NULL)
182 nfs_put_lock_context(dreq->l_ctx);
183 if (dreq->ctx != NULL)
184 put_nfs_open_context(dreq->ctx);
185 kmem_cache_free(nfs_direct_cachep, dreq);
188 static void nfs_direct_req_release(struct nfs_direct_req *dreq)
190 kref_put(&dreq->kref, nfs_direct_req_free);
193 ssize_t nfs_dreq_bytes_left(struct nfs_direct_req *dreq)
195 return dreq->bytes_left;
197 EXPORT_SYMBOL_GPL(nfs_dreq_bytes_left);
200 * Collects and returns the final error value/byte-count.
202 static ssize_t nfs_direct_wait(struct nfs_direct_req *dreq)
204 ssize_t result = -EIOCBQUEUED;
206 /* Async requests don't wait here */
210 result = wait_for_completion_killable(&dreq->completion);
213 result = dreq->error;
215 result = dreq->count;
218 return (ssize_t) result;
222 * Synchronous I/O uses a stack-allocated iocb. Thus we can't trust
223 * the iocb is still valid here if this is a synchronous request.
225 static void nfs_direct_complete(struct nfs_direct_req *dreq, bool write)
227 struct inode *inode = dreq->inode;
229 if (dreq->iocb && write) {
230 loff_t pos = dreq->iocb->ki_pos + dreq->count;
232 spin_lock(&inode->i_lock);
233 if (i_size_read(inode) < pos)
234 i_size_write(inode, pos);
235 spin_unlock(&inode->i_lock);
239 nfs_zap_mapping(inode, inode->i_mapping);
241 inode_dio_done(inode);
244 long res = (long) dreq->error;
246 res = (long) dreq->count;
247 aio_complete(dreq->iocb, res, 0);
250 complete_all(&dreq->completion);
252 nfs_direct_req_release(dreq);
255 static void nfs_direct_readpage_release(struct nfs_page *req)
257 dprintk("NFS: direct read done (%s/%llu %d@%lld)\n",
258 req->wb_context->dentry->d_inode->i_sb->s_id,
259 (unsigned long long)NFS_FILEID(req->wb_context->dentry->d_inode),
261 (long long)req_offset(req));
262 nfs_release_request(req);
265 static void nfs_direct_read_completion(struct nfs_pgio_header *hdr)
267 unsigned long bytes = 0;
268 struct nfs_direct_req *dreq = hdr->dreq;
270 if (test_bit(NFS_IOHDR_REDO, &hdr->flags))
273 spin_lock(&dreq->lock);
274 if (test_bit(NFS_IOHDR_ERROR, &hdr->flags) && (hdr->good_bytes == 0))
275 dreq->error = hdr->error;
277 dreq->count += hdr->good_bytes;
278 spin_unlock(&dreq->lock);
280 while (!list_empty(&hdr->pages)) {
281 struct nfs_page *req = nfs_list_entry(hdr->pages.next);
282 struct page *page = req->wb_page;
284 if (!PageCompound(page) && bytes < hdr->good_bytes)
285 set_page_dirty(page);
286 bytes += req->wb_bytes;
287 nfs_list_remove_request(req);
288 nfs_direct_readpage_release(req);
292 nfs_direct_complete(dreq, false);
296 static void nfs_read_sync_pgio_error(struct list_head *head)
298 struct nfs_page *req;
300 while (!list_empty(head)) {
301 req = nfs_list_entry(head->next);
302 nfs_list_remove_request(req);
303 nfs_release_request(req);
307 static void nfs_direct_pgio_init(struct nfs_pgio_header *hdr)
312 static const struct nfs_pgio_completion_ops nfs_direct_read_completion_ops = {
313 .error_cleanup = nfs_read_sync_pgio_error,
314 .init_hdr = nfs_direct_pgio_init,
315 .completion = nfs_direct_read_completion,
319 * For each rsize'd chunk of the user's buffer, dispatch an NFS READ
320 * operation. If nfs_readdata_alloc() or get_user_pages() fails,
321 * bail and stop sending more reads. Read length accounting is
322 * handled automatically by nfs_direct_read_result(). Otherwise, if
323 * no requests have been sent, just return an error.
326 static ssize_t nfs_direct_read_schedule_iovec(struct nfs_direct_req *dreq,
327 struct iov_iter *iter,
330 struct nfs_pageio_descriptor desc;
331 struct inode *inode = dreq->inode;
332 ssize_t result = -EINVAL;
333 size_t requested_bytes = 0;
334 size_t rsize = max_t(size_t, NFS_SERVER(inode)->rsize, PAGE_SIZE);
336 NFS_PROTO(dreq->inode)->read_pageio_init(&desc, dreq->inode,
337 &nfs_direct_read_completion_ops);
340 atomic_inc(&inode->i_dio_count);
342 while (iov_iter_count(iter)) {
343 struct page **pagevec;
348 result = iov_iter_get_pages_alloc(iter, &pagevec,
354 iov_iter_advance(iter, bytes);
355 npages = (result + pgbase + PAGE_SIZE - 1) / PAGE_SIZE;
356 for (i = 0; i < npages; i++) {
357 struct nfs_page *req;
358 unsigned int req_len = min_t(size_t, bytes, PAGE_SIZE - pgbase);
359 /* XXX do we need to do the eof zeroing found in async_filler? */
360 req = nfs_create_request(dreq->ctx, dreq->inode,
364 result = PTR_ERR(req);
367 req->wb_index = pos >> PAGE_SHIFT;
368 req->wb_offset = pos & ~PAGE_MASK;
369 if (!nfs_pageio_add_request(&desc, req)) {
370 result = desc.pg_error;
371 nfs_release_request(req);
376 requested_bytes += req_len;
378 dreq->bytes_left -= req_len;
380 nfs_direct_release_pages(pagevec, npages);
386 nfs_pageio_complete(&desc);
389 * If no bytes were started, return the error, and let the
390 * generic layer handle the completion.
392 if (requested_bytes == 0) {
393 inode_dio_done(inode);
394 nfs_direct_req_release(dreq);
395 return result < 0 ? result : -EIO;
399 nfs_direct_complete(dreq, false);
404 * nfs_file_direct_read - file direct read operation for NFS files
405 * @iocb: target I/O control block
406 * @iter: vector of user buffers into which to read data
407 * @pos: byte offset in file where reading starts
409 * We use this function for direct reads instead of calling
410 * generic_file_aio_read() in order to avoid gfar's check to see if
411 * the request starts before the end of the file. For that check
412 * to work, we must generate a GETATTR before each direct read, and
413 * even then there is a window between the GETATTR and the subsequent
414 * READ where the file size could change. Our preference is simply
415 * to do all reads the application wants, and the server will take
416 * care of managing the end of file boundary.
418 * This function also eliminates unnecessarily updating the file's
419 * atime locally, as the NFS server sets the file's atime, and this
420 * client must read the updated atime from the server back into its
423 ssize_t nfs_file_direct_read(struct kiocb *iocb, struct iov_iter *iter,
424 loff_t pos, bool uio)
426 struct file *file = iocb->ki_filp;
427 struct address_space *mapping = file->f_mapping;
428 struct inode *inode = mapping->host;
429 struct nfs_direct_req *dreq;
430 struct nfs_lock_context *l_ctx;
431 ssize_t result = -EINVAL;
432 size_t count = iov_iter_count(iter);
433 nfs_add_stats(mapping->host, NFSIOS_DIRECTREADBYTES, count);
435 dfprintk(FILE, "NFS: direct read(%pD2, %zd@%Ld)\n",
436 file, count, (long long) pos);
442 mutex_lock(&inode->i_mutex);
443 result = nfs_sync_mapping(mapping);
447 task_io_account_read(count);
450 dreq = nfs_direct_req_alloc();
455 dreq->bytes_left = count;
456 dreq->ctx = get_nfs_open_context(nfs_file_open_context(iocb->ki_filp));
457 l_ctx = nfs_get_lock_context(dreq->ctx);
459 result = PTR_ERR(l_ctx);
463 if (!is_sync_kiocb(iocb))
466 NFS_I(inode)->read_io += count;
467 result = nfs_direct_read_schedule_iovec(dreq, iter, pos);
469 mutex_unlock(&inode->i_mutex);
472 result = nfs_direct_wait(dreq);
474 iocb->ki_pos = pos + result;
477 nfs_direct_req_release(dreq);
481 nfs_direct_req_release(dreq);
483 mutex_unlock(&inode->i_mutex);
488 #if IS_ENABLED(CONFIG_NFS_V3) || IS_ENABLED(CONFIG_NFS_V4)
489 static void nfs_direct_write_reschedule(struct nfs_direct_req *dreq)
491 struct nfs_pageio_descriptor desc;
492 struct nfs_page *req, *tmp;
494 struct nfs_commit_info cinfo;
497 nfs_init_cinfo_from_dreq(&cinfo, dreq);
498 pnfs_recover_commit_reqs(dreq->inode, &reqs, &cinfo);
499 spin_lock(cinfo.lock);
500 nfs_scan_commit_list(&cinfo.mds->list, &reqs, &cinfo, 0);
501 spin_unlock(cinfo.lock);
506 NFS_PROTO(dreq->inode)->write_pageio_init(&desc, dreq->inode, FLUSH_STABLE,
507 &nfs_direct_write_completion_ops);
510 list_for_each_entry_safe(req, tmp, &reqs, wb_list) {
511 if (!nfs_pageio_add_request(&desc, req)) {
512 nfs_list_remove_request(req);
513 nfs_list_add_request(req, &failed);
514 spin_lock(cinfo.lock);
517 spin_unlock(cinfo.lock);
519 nfs_release_request(req);
521 nfs_pageio_complete(&desc);
523 while (!list_empty(&failed)) {
524 req = nfs_list_entry(failed.next);
525 nfs_list_remove_request(req);
526 nfs_unlock_and_release_request(req);
530 nfs_direct_write_complete(dreq, dreq->inode);
533 static void nfs_direct_commit_complete(struct nfs_commit_data *data)
535 struct nfs_direct_req *dreq = data->dreq;
536 struct nfs_commit_info cinfo;
537 struct nfs_page *req;
538 int status = data->task.tk_status;
540 nfs_init_cinfo_from_dreq(&cinfo, dreq);
542 dprintk("NFS: %5u commit failed with error %d.\n",
543 data->task.tk_pid, status);
544 dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
545 } else if (memcmp(&dreq->verf, &data->verf, sizeof(data->verf))) {
546 dprintk("NFS: %5u commit verify failed\n", data->task.tk_pid);
547 dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
550 dprintk("NFS: %5u commit returned %d\n", data->task.tk_pid, status);
551 while (!list_empty(&data->pages)) {
552 req = nfs_list_entry(data->pages.next);
553 nfs_list_remove_request(req);
554 if (dreq->flags == NFS_ODIRECT_RESCHED_WRITES) {
555 /* Note the rewrite will go through mds */
556 nfs_mark_request_commit(req, NULL, &cinfo);
558 nfs_release_request(req);
559 nfs_unlock_and_release_request(req);
562 if (atomic_dec_and_test(&cinfo.mds->rpcs_out))
563 nfs_direct_write_complete(dreq, data->inode);
566 static void nfs_direct_error_cleanup(struct nfs_inode *nfsi)
568 /* There is no lock to clear */
571 static const struct nfs_commit_completion_ops nfs_direct_commit_completion_ops = {
572 .completion = nfs_direct_commit_complete,
573 .error_cleanup = nfs_direct_error_cleanup,
576 static void nfs_direct_commit_schedule(struct nfs_direct_req *dreq)
579 struct nfs_commit_info cinfo;
582 nfs_init_cinfo_from_dreq(&cinfo, dreq);
583 nfs_scan_commit(dreq->inode, &mds_list, &cinfo);
584 res = nfs_generic_commit_list(dreq->inode, &mds_list, 0, &cinfo);
585 if (res < 0) /* res == -ENOMEM */
586 nfs_direct_write_reschedule(dreq);
589 static void nfs_direct_write_schedule_work(struct work_struct *work)
591 struct nfs_direct_req *dreq = container_of(work, struct nfs_direct_req, work);
592 int flags = dreq->flags;
596 case NFS_ODIRECT_DO_COMMIT:
597 nfs_direct_commit_schedule(dreq);
599 case NFS_ODIRECT_RESCHED_WRITES:
600 nfs_direct_write_reschedule(dreq);
603 nfs_direct_complete(dreq, true);
607 static void nfs_direct_write_complete(struct nfs_direct_req *dreq, struct inode *inode)
609 schedule_work(&dreq->work); /* Calls nfs_direct_write_schedule_work */
613 static void nfs_direct_write_schedule_work(struct work_struct *work)
617 static void nfs_direct_write_complete(struct nfs_direct_req *dreq, struct inode *inode)
619 nfs_direct_complete(dreq, true);
623 static void nfs_direct_write_completion(struct nfs_pgio_header *hdr)
625 struct nfs_direct_req *dreq = hdr->dreq;
626 struct nfs_commit_info cinfo;
628 struct nfs_page *req = nfs_list_entry(hdr->pages.next);
630 if (test_bit(NFS_IOHDR_REDO, &hdr->flags))
633 nfs_init_cinfo_from_dreq(&cinfo, dreq);
635 spin_lock(&dreq->lock);
637 if (test_bit(NFS_IOHDR_ERROR, &hdr->flags)) {
639 dreq->error = hdr->error;
641 if (dreq->error != 0)
642 bit = NFS_IOHDR_ERROR;
644 dreq->count += hdr->good_bytes;
645 if (test_bit(NFS_IOHDR_NEED_RESCHED, &hdr->flags)) {
646 dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
647 bit = NFS_IOHDR_NEED_RESCHED;
648 } else if (test_bit(NFS_IOHDR_NEED_COMMIT, &hdr->flags)) {
649 if (dreq->flags == NFS_ODIRECT_RESCHED_WRITES)
650 bit = NFS_IOHDR_NEED_RESCHED;
651 else if (dreq->flags == 0) {
652 memcpy(&dreq->verf, hdr->verf,
654 bit = NFS_IOHDR_NEED_COMMIT;
655 dreq->flags = NFS_ODIRECT_DO_COMMIT;
656 } else if (dreq->flags == NFS_ODIRECT_DO_COMMIT) {
657 if (memcmp(&dreq->verf, hdr->verf, sizeof(dreq->verf))) {
658 dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
659 bit = NFS_IOHDR_NEED_RESCHED;
661 bit = NFS_IOHDR_NEED_COMMIT;
665 spin_unlock(&dreq->lock);
667 while (!list_empty(&hdr->pages)) {
668 req = nfs_list_entry(hdr->pages.next);
669 nfs_list_remove_request(req);
671 case NFS_IOHDR_NEED_RESCHED:
672 case NFS_IOHDR_NEED_COMMIT:
673 kref_get(&req->wb_kref);
674 nfs_mark_request_commit(req, hdr->lseg, &cinfo);
676 nfs_unlock_and_release_request(req);
681 nfs_direct_write_complete(dreq, hdr->inode);
685 static void nfs_write_sync_pgio_error(struct list_head *head)
687 struct nfs_page *req;
689 while (!list_empty(head)) {
690 req = nfs_list_entry(head->next);
691 nfs_list_remove_request(req);
692 nfs_unlock_and_release_request(req);
696 static const struct nfs_pgio_completion_ops nfs_direct_write_completion_ops = {
697 .error_cleanup = nfs_write_sync_pgio_error,
698 .init_hdr = nfs_direct_pgio_init,
699 .completion = nfs_direct_write_completion,
704 * NB: Return the value of the first error return code. Subsequent
705 * errors after the first one are ignored.
708 * For each wsize'd chunk of the user's buffer, dispatch an NFS WRITE
709 * operation. If nfs_writedata_alloc() or get_user_pages() fails,
710 * bail and stop sending more writes. Write length accounting is
711 * handled automatically by nfs_direct_write_result(). Otherwise, if
712 * no requests have been sent, just return an error.
714 static ssize_t nfs_direct_write_schedule_iovec(struct nfs_direct_req *dreq,
715 struct iov_iter *iter,
718 struct nfs_pageio_descriptor desc;
719 struct inode *inode = dreq->inode;
721 size_t requested_bytes = 0;
722 size_t wsize = max_t(size_t, NFS_SERVER(inode)->wsize, PAGE_SIZE);
724 NFS_PROTO(inode)->write_pageio_init(&desc, inode, FLUSH_COND_STABLE,
725 &nfs_direct_write_completion_ops);
728 atomic_inc(&inode->i_dio_count);
730 NFS_I(inode)->write_io += iov_iter_count(iter);
731 while (iov_iter_count(iter)) {
732 struct page **pagevec;
737 result = iov_iter_get_pages_alloc(iter, &pagevec,
743 iov_iter_advance(iter, bytes);
744 npages = (result + pgbase + PAGE_SIZE - 1) / PAGE_SIZE;
745 for (i = 0; i < npages; i++) {
746 struct nfs_page *req;
747 unsigned int req_len = min_t(size_t, bytes, PAGE_SIZE - pgbase);
749 req = nfs_create_request(dreq->ctx, inode,
753 result = PTR_ERR(req);
756 nfs_lock_request(req);
757 req->wb_index = pos >> PAGE_SHIFT;
758 req->wb_offset = pos & ~PAGE_MASK;
759 if (!nfs_pageio_add_request(&desc, req)) {
760 result = desc.pg_error;
761 nfs_unlock_and_release_request(req);
766 requested_bytes += req_len;
768 dreq->bytes_left -= req_len;
770 nfs_direct_release_pages(pagevec, npages);
775 nfs_pageio_complete(&desc);
778 * If no bytes were started, return the error, and let the
779 * generic layer handle the completion.
781 if (requested_bytes == 0) {
782 inode_dio_done(inode);
783 nfs_direct_req_release(dreq);
784 return result < 0 ? result : -EIO;
788 nfs_direct_write_complete(dreq, dreq->inode);
793 * nfs_file_direct_write - file direct write operation for NFS files
794 * @iocb: target I/O control block
795 * @iter: vector of user buffers from which to write data
796 * @pos: byte offset in file where writing starts
798 * We use this function for direct writes instead of calling
799 * generic_file_aio_write() in order to avoid taking the inode
800 * semaphore and updating the i_size. The NFS server will set
801 * the new i_size and this client must read the updated size
802 * back into its cache. We let the server do generic write
803 * parameter checking and report problems.
805 * We eliminate local atime updates, see direct read above.
807 * We avoid unnecessary page cache invalidations for normal cached
808 * readers of this file.
810 * Note that O_APPEND is not supported for NFS direct writes, as there
811 * is no atomic O_APPEND write facility in the NFS protocol.
813 ssize_t nfs_file_direct_write(struct kiocb *iocb, struct iov_iter *iter,
814 loff_t pos, bool uio)
816 ssize_t result = -EINVAL;
817 struct file *file = iocb->ki_filp;
818 struct address_space *mapping = file->f_mapping;
819 struct inode *inode = mapping->host;
820 struct nfs_direct_req *dreq;
821 struct nfs_lock_context *l_ctx;
823 size_t count = iov_iter_count(iter);
824 end = (pos + count - 1) >> PAGE_CACHE_SHIFT;
826 nfs_add_stats(mapping->host, NFSIOS_DIRECTWRITTENBYTES, count);
828 dfprintk(FILE, "NFS: direct write(%pD2, %zd@%Ld)\n",
829 file, count, (long long) pos);
831 result = generic_write_checks(file, &pos, &count, 0);
836 if ((ssize_t) count < 0)
842 mutex_lock(&inode->i_mutex);
844 result = nfs_sync_mapping(mapping);
848 if (mapping->nrpages) {
849 result = invalidate_inode_pages2_range(mapping,
850 pos >> PAGE_CACHE_SHIFT, end);
855 task_io_account_write(count);
858 dreq = nfs_direct_req_alloc();
863 dreq->bytes_left = count;
864 dreq->ctx = get_nfs_open_context(nfs_file_open_context(iocb->ki_filp));
865 l_ctx = nfs_get_lock_context(dreq->ctx);
867 result = PTR_ERR(l_ctx);
871 if (!is_sync_kiocb(iocb))
874 result = nfs_direct_write_schedule_iovec(dreq, iter, pos);
876 if (mapping->nrpages) {
877 invalidate_inode_pages2_range(mapping,
878 pos >> PAGE_CACHE_SHIFT, end);
881 mutex_unlock(&inode->i_mutex);
884 result = nfs_direct_wait(dreq);
886 struct inode *inode = mapping->host;
888 iocb->ki_pos = pos + result;
889 spin_lock(&inode->i_lock);
890 if (i_size_read(inode) < iocb->ki_pos)
891 i_size_write(inode, iocb->ki_pos);
892 spin_unlock(&inode->i_lock);
895 nfs_direct_req_release(dreq);
899 nfs_direct_req_release(dreq);
901 mutex_unlock(&inode->i_mutex);
907 * nfs_init_directcache - create a slab cache for nfs_direct_req structures
910 int __init nfs_init_directcache(void)
912 nfs_direct_cachep = kmem_cache_create("nfs_direct_cache",
913 sizeof(struct nfs_direct_req),
914 0, (SLAB_RECLAIM_ACCOUNT|
917 if (nfs_direct_cachep == NULL)
924 * nfs_destroy_directcache - destroy the slab cache for nfs_direct_req structures
927 void nfs_destroy_directcache(void)
929 kmem_cache_destroy(nfs_direct_cachep);