1 // SPDX-License-Identifier: GPL-2.0-only
3 * linux/fs/nfs/direct.c
5 * Copyright (C) 2003 by Chuck Lever <cel@netapp.com>
7 * High-performance uncached I/O for the Linux NFS client
9 * There are important applications whose performance or correctness
10 * depends on uncached access to file data. Database clusters
11 * (multiple copies of the same instance running on separate hosts)
12 * implement their own cache coherency protocol that subsumes file
13 * system cache protocols. Applications that process datasets
14 * considerably larger than the client's memory do not always benefit
15 * from a local cache. A streaming video server, for instance, has no
16 * need to cache the contents of a file.
18 * When an application requests uncached I/O, all read and write requests
19 * are made directly to the server; data stored or fetched via these
20 * requests is not cached in the Linux page cache. The client does not
21 * correct unaligned requests from applications. All requested bytes are
22 * held on permanent storage before a direct write system call returns to
25 * Solaris implements an uncached I/O facility called directio() that
26 * is used for backups and sequential I/O to very large files. Solaris
27 * also supports uncaching whole NFS partitions with "-o forcedirectio,"
28 * an undocumented mount option.
30 * Designed by Jeff Kimmel, Chuck Lever, and Trond Myklebust, with
31 * help from Andrew Morton.
33 * 18 Dec 2001 Initial implementation for 2.4 --cel
34 * 08 Jul 2002 Version for 2.4.19, with bug fixes --trondmy
35 * 08 Jun 2003 Port to 2.5 APIs --cel
36 * 31 Mar 2004 Handle direct I/O without VFS support --cel
37 * 15 Sep 2004 Parallel async reads --cel
38 * 04 May 2005 support O_DIRECT with aio --cel
42 #include <linux/errno.h>
43 #include <linux/sched.h>
44 #include <linux/kernel.h>
45 #include <linux/file.h>
46 #include <linux/pagemap.h>
47 #include <linux/kref.h>
48 #include <linux/slab.h>
49 #include <linux/task_io_accounting_ops.h>
50 #include <linux/module.h>
52 #include <linux/nfs_fs.h>
53 #include <linux/nfs_page.h>
54 #include <linux/sunrpc/clnt.h>
56 #include <linux/uaccess.h>
57 #include <linux/atomic.h>
65 #define NFSDBG_FACILITY NFSDBG_VFS
67 static struct kmem_cache *nfs_direct_cachep;
69 static const struct nfs_pgio_completion_ops nfs_direct_write_completion_ops;
70 static const struct nfs_commit_completion_ops nfs_direct_commit_completion_ops;
71 static void nfs_direct_write_complete(struct nfs_direct_req *dreq);
72 static void nfs_direct_write_schedule_work(struct work_struct *work);
74 static inline void get_dreq(struct nfs_direct_req *dreq)
76 atomic_inc(&dreq->io_count);
79 static inline int put_dreq(struct nfs_direct_req *dreq)
81 return atomic_dec_and_test(&dreq->io_count);
85 nfs_direct_handle_truncated(struct nfs_direct_req *dreq,
86 const struct nfs_pgio_header *hdr,
89 if (!(test_bit(NFS_IOHDR_ERROR, &hdr->flags) ||
90 test_bit(NFS_IOHDR_EOF, &hdr->flags)))
92 if (dreq->max_count >= dreq_len) {
93 dreq->max_count = dreq_len;
94 if (dreq->count > dreq_len)
95 dreq->count = dreq_len;
97 if (test_bit(NFS_IOHDR_ERROR, &hdr->flags))
98 dreq->error = hdr->error;
99 else /* Clear outstanding error if this is EOF */
105 nfs_direct_count_bytes(struct nfs_direct_req *dreq,
106 const struct nfs_pgio_header *hdr)
108 loff_t hdr_end = hdr->io_start + hdr->good_bytes;
109 ssize_t dreq_len = 0;
111 if (hdr_end > dreq->io_start)
112 dreq_len = hdr_end - dreq->io_start;
114 nfs_direct_handle_truncated(dreq, hdr, dreq_len);
116 if (dreq_len > dreq->max_count)
117 dreq_len = dreq->max_count;
119 if (dreq->count < dreq_len)
120 dreq->count = dreq_len;
124 * nfs_swap_rw - NFS address space operation for swap I/O
125 * @iocb: target I/O control block
128 * Perform IO to the swap-file. This is much like direct IO.
130 int nfs_swap_rw(struct kiocb *iocb, struct iov_iter *iter)
134 VM_BUG_ON(iov_iter_count(iter) != PAGE_SIZE);
136 if (iov_iter_rw(iter) == READ)
137 ret = nfs_file_direct_read(iocb, iter, true);
139 ret = nfs_file_direct_write(iocb, iter, true);
145 static void nfs_direct_release_pages(struct page **pages, unsigned int npages)
148 for (i = 0; i < npages; i++)
152 void nfs_init_cinfo_from_dreq(struct nfs_commit_info *cinfo,
153 struct nfs_direct_req *dreq)
155 cinfo->inode = dreq->inode;
156 cinfo->mds = &dreq->mds_cinfo;
157 cinfo->ds = &dreq->ds_cinfo;
159 cinfo->completion_ops = &nfs_direct_commit_completion_ops;
162 static inline struct nfs_direct_req *nfs_direct_req_alloc(void)
164 struct nfs_direct_req *dreq;
166 dreq = kmem_cache_zalloc(nfs_direct_cachep, GFP_KERNEL);
170 kref_init(&dreq->kref);
171 kref_get(&dreq->kref);
172 init_completion(&dreq->completion);
173 INIT_LIST_HEAD(&dreq->mds_cinfo.list);
174 pnfs_init_ds_commit_info(&dreq->ds_cinfo);
175 INIT_WORK(&dreq->work, nfs_direct_write_schedule_work);
176 spin_lock_init(&dreq->lock);
181 static void nfs_direct_req_free(struct kref *kref)
183 struct nfs_direct_req *dreq = container_of(kref, struct nfs_direct_req, kref);
185 pnfs_release_ds_info(&dreq->ds_cinfo, dreq->inode);
186 if (dreq->l_ctx != NULL)
187 nfs_put_lock_context(dreq->l_ctx);
188 if (dreq->ctx != NULL)
189 put_nfs_open_context(dreq->ctx);
190 kmem_cache_free(nfs_direct_cachep, dreq);
193 static void nfs_direct_req_release(struct nfs_direct_req *dreq)
195 kref_put(&dreq->kref, nfs_direct_req_free);
198 ssize_t nfs_dreq_bytes_left(struct nfs_direct_req *dreq)
200 return dreq->bytes_left;
202 EXPORT_SYMBOL_GPL(nfs_dreq_bytes_left);
205 * Collects and returns the final error value/byte-count.
207 static ssize_t nfs_direct_wait(struct nfs_direct_req *dreq)
209 ssize_t result = -EIOCBQUEUED;
211 /* Async requests don't wait here */
215 result = wait_for_completion_killable(&dreq->completion);
218 result = dreq->count;
219 WARN_ON_ONCE(dreq->count < 0);
222 result = dreq->error;
225 return (ssize_t) result;
229 * Synchronous I/O uses a stack-allocated iocb. Thus we can't trust
230 * the iocb is still valid here if this is a synchronous request.
232 static void nfs_direct_complete(struct nfs_direct_req *dreq)
234 struct inode *inode = dreq->inode;
236 inode_dio_end(inode);
239 long res = (long) dreq->error;
240 if (dreq->count != 0) {
241 res = (long) dreq->count;
242 WARN_ON_ONCE(dreq->count < 0);
244 dreq->iocb->ki_complete(dreq->iocb, res);
247 complete(&dreq->completion);
249 nfs_direct_req_release(dreq);
252 static void nfs_direct_read_completion(struct nfs_pgio_header *hdr)
254 unsigned long bytes = 0;
255 struct nfs_direct_req *dreq = hdr->dreq;
257 spin_lock(&dreq->lock);
258 if (test_bit(NFS_IOHDR_REDO, &hdr->flags)) {
259 spin_unlock(&dreq->lock);
263 nfs_direct_count_bytes(dreq, hdr);
264 spin_unlock(&dreq->lock);
266 while (!list_empty(&hdr->pages)) {
267 struct nfs_page *req = nfs_list_entry(hdr->pages.next);
268 struct page *page = req->wb_page;
270 if (!PageCompound(page) && bytes < hdr->good_bytes &&
271 (dreq->flags == NFS_ODIRECT_SHOULD_DIRTY))
272 set_page_dirty(page);
273 bytes += req->wb_bytes;
274 nfs_list_remove_request(req);
275 nfs_release_request(req);
279 nfs_direct_complete(dreq);
283 static void nfs_read_sync_pgio_error(struct list_head *head, int error)
285 struct nfs_page *req;
287 while (!list_empty(head)) {
288 req = nfs_list_entry(head->next);
289 nfs_list_remove_request(req);
290 nfs_release_request(req);
294 static void nfs_direct_pgio_init(struct nfs_pgio_header *hdr)
299 static const struct nfs_pgio_completion_ops nfs_direct_read_completion_ops = {
300 .error_cleanup = nfs_read_sync_pgio_error,
301 .init_hdr = nfs_direct_pgio_init,
302 .completion = nfs_direct_read_completion,
306 * For each rsize'd chunk of the user's buffer, dispatch an NFS READ
307 * operation. If nfs_readdata_alloc() or get_user_pages() fails,
308 * bail and stop sending more reads. Read length accounting is
309 * handled automatically by nfs_direct_read_result(). Otherwise, if
310 * no requests have been sent, just return an error.
313 static ssize_t nfs_direct_read_schedule_iovec(struct nfs_direct_req *dreq,
314 struct iov_iter *iter,
317 struct nfs_pageio_descriptor desc;
318 struct inode *inode = dreq->inode;
319 ssize_t result = -EINVAL;
320 size_t requested_bytes = 0;
321 size_t rsize = max_t(size_t, NFS_SERVER(inode)->rsize, PAGE_SIZE);
323 nfs_pageio_init_read(&desc, dreq->inode, false,
324 &nfs_direct_read_completion_ops);
327 inode_dio_begin(inode);
329 while (iov_iter_count(iter)) {
330 struct page **pagevec;
335 result = iov_iter_get_pages_alloc2(iter, &pagevec,
341 npages = (result + pgbase + PAGE_SIZE - 1) / PAGE_SIZE;
342 for (i = 0; i < npages; i++) {
343 struct nfs_page *req;
344 unsigned int req_len = min_t(size_t, bytes, PAGE_SIZE - pgbase);
345 /* XXX do we need to do the eof zeroing found in async_filler? */
346 req = nfs_create_request(dreq->ctx, pagevec[i],
349 result = PTR_ERR(req);
352 req->wb_index = pos >> PAGE_SHIFT;
353 req->wb_offset = pos & ~PAGE_MASK;
354 if (!nfs_pageio_add_request(&desc, req)) {
355 result = desc.pg_error;
356 nfs_release_request(req);
361 requested_bytes += req_len;
363 dreq->bytes_left -= req_len;
365 nfs_direct_release_pages(pagevec, npages);
371 nfs_pageio_complete(&desc);
374 * If no bytes were started, return the error, and let the
375 * generic layer handle the completion.
377 if (requested_bytes == 0) {
378 inode_dio_end(inode);
379 nfs_direct_req_release(dreq);
380 return result < 0 ? result : -EIO;
384 nfs_direct_complete(dreq);
385 return requested_bytes;
389 * nfs_file_direct_read - file direct read operation for NFS files
390 * @iocb: target I/O control block
391 * @iter: vector of user buffers into which to read data
392 * @swap: flag indicating this is swap IO, not O_DIRECT IO
394 * We use this function for direct reads instead of calling
395 * generic_file_aio_read() in order to avoid gfar's check to see if
396 * the request starts before the end of the file. For that check
397 * to work, we must generate a GETATTR before each direct read, and
398 * even then there is a window between the GETATTR and the subsequent
399 * READ where the file size could change. Our preference is simply
400 * to do all reads the application wants, and the server will take
401 * care of managing the end of file boundary.
403 * This function also eliminates unnecessarily updating the file's
404 * atime locally, as the NFS server sets the file's atime, and this
405 * client must read the updated atime from the server back into its
408 ssize_t nfs_file_direct_read(struct kiocb *iocb, struct iov_iter *iter,
411 struct file *file = iocb->ki_filp;
412 struct address_space *mapping = file->f_mapping;
413 struct inode *inode = mapping->host;
414 struct nfs_direct_req *dreq;
415 struct nfs_lock_context *l_ctx;
416 ssize_t result, requested;
417 size_t count = iov_iter_count(iter);
418 nfs_add_stats(mapping->host, NFSIOS_DIRECTREADBYTES, count);
420 dfprintk(FILE, "NFS: direct read(%pD2, %zd@%Ld)\n",
421 file, count, (long long) iocb->ki_pos);
427 task_io_account_read(count);
430 dreq = nfs_direct_req_alloc();
435 dreq->bytes_left = dreq->max_count = count;
436 dreq->io_start = iocb->ki_pos;
437 dreq->ctx = get_nfs_open_context(nfs_file_open_context(iocb->ki_filp));
438 l_ctx = nfs_get_lock_context(dreq->ctx);
440 result = PTR_ERR(l_ctx);
441 nfs_direct_req_release(dreq);
445 if (!is_sync_kiocb(iocb))
448 if (user_backed_iter(iter))
449 dreq->flags = NFS_ODIRECT_SHOULD_DIRTY;
452 nfs_start_io_direct(inode);
454 NFS_I(inode)->read_io += count;
455 requested = nfs_direct_read_schedule_iovec(dreq, iter, iocb->ki_pos);
458 nfs_end_io_direct(inode);
461 result = nfs_direct_wait(dreq);
464 iocb->ki_pos += result;
466 iov_iter_revert(iter, requested);
472 nfs_direct_req_release(dreq);
477 static void nfs_direct_join_group(struct list_head *list, struct inode *inode)
479 struct nfs_page *req, *subreq;
481 list_for_each_entry(req, list, wb_list) {
482 if (req->wb_head != req)
484 subreq = req->wb_this_page;
489 * Remove subrequests from this list before freeing
490 * them in the call to nfs_join_page_group().
492 if (!list_empty(&subreq->wb_list)) {
493 nfs_list_remove_request(subreq);
494 nfs_release_request(subreq);
496 } while ((subreq = subreq->wb_this_page) != req);
497 nfs_join_page_group(req, inode);
502 nfs_direct_write_scan_commit_list(struct inode *inode,
503 struct list_head *list,
504 struct nfs_commit_info *cinfo)
506 mutex_lock(&NFS_I(cinfo->inode)->commit_mutex);
507 pnfs_recover_commit_reqs(list, cinfo);
508 nfs_scan_commit_list(&cinfo->mds->list, list, cinfo, 0);
509 mutex_unlock(&NFS_I(cinfo->inode)->commit_mutex);
512 static void nfs_direct_write_reschedule(struct nfs_direct_req *dreq)
514 struct nfs_pageio_descriptor desc;
515 struct nfs_page *req, *tmp;
517 struct nfs_commit_info cinfo;
520 nfs_init_cinfo_from_dreq(&cinfo, dreq);
521 nfs_direct_write_scan_commit_list(dreq->inode, &reqs, &cinfo);
523 nfs_direct_join_group(&reqs, dreq->inode);
527 list_for_each_entry(req, &reqs, wb_list)
528 dreq->max_count += req->wb_bytes;
529 nfs_clear_pnfs_ds_commit_verifiers(&dreq->ds_cinfo);
532 nfs_pageio_init_write(&desc, dreq->inode, FLUSH_STABLE, false,
533 &nfs_direct_write_completion_ops);
536 list_for_each_entry_safe(req, tmp, &reqs, wb_list) {
537 /* Bump the transmission count */
539 if (!nfs_pageio_add_request(&desc, req)) {
540 nfs_list_move_request(req, &failed);
541 spin_lock(&cinfo.inode->i_lock);
543 if (desc.pg_error < 0)
544 dreq->error = desc.pg_error;
547 spin_unlock(&cinfo.inode->i_lock);
549 nfs_release_request(req);
551 nfs_pageio_complete(&desc);
553 while (!list_empty(&failed)) {
554 req = nfs_list_entry(failed.next);
555 nfs_list_remove_request(req);
556 nfs_unlock_and_release_request(req);
560 nfs_direct_write_complete(dreq);
563 static void nfs_direct_commit_complete(struct nfs_commit_data *data)
565 const struct nfs_writeverf *verf = data->res.verf;
566 struct nfs_direct_req *dreq = data->dreq;
567 struct nfs_commit_info cinfo;
568 struct nfs_page *req;
569 int status = data->task.tk_status;
571 trace_nfs_direct_commit_complete(dreq);
574 /* Errors in commit are fatal */
575 dreq->error = status;
578 dreq->flags = NFS_ODIRECT_DONE;
580 status = dreq->error;
583 nfs_init_cinfo_from_dreq(&cinfo, dreq);
585 while (!list_empty(&data->pages)) {
586 req = nfs_list_entry(data->pages.next);
587 nfs_list_remove_request(req);
588 if (status >= 0 && !nfs_write_match_verf(verf, req)) {
589 dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
591 * Despite the reboot, the write was successful,
595 nfs_mark_request_commit(req, NULL, &cinfo, 0);
596 } else /* Error or match */
597 nfs_release_request(req);
598 nfs_unlock_and_release_request(req);
601 if (nfs_commit_end(cinfo.mds))
602 nfs_direct_write_complete(dreq);
605 static void nfs_direct_resched_write(struct nfs_commit_info *cinfo,
606 struct nfs_page *req)
608 struct nfs_direct_req *dreq = cinfo->dreq;
610 trace_nfs_direct_resched_write(dreq);
612 spin_lock(&dreq->lock);
613 if (dreq->flags != NFS_ODIRECT_DONE)
614 dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
615 spin_unlock(&dreq->lock);
616 nfs_mark_request_commit(req, NULL, cinfo, 0);
619 static const struct nfs_commit_completion_ops nfs_direct_commit_completion_ops = {
620 .completion = nfs_direct_commit_complete,
621 .resched_write = nfs_direct_resched_write,
624 static void nfs_direct_commit_schedule(struct nfs_direct_req *dreq)
627 struct nfs_commit_info cinfo;
630 nfs_init_cinfo_from_dreq(&cinfo, dreq);
631 nfs_scan_commit(dreq->inode, &mds_list, &cinfo);
632 res = nfs_generic_commit_list(dreq->inode, &mds_list, 0, &cinfo);
633 if (res < 0) /* res == -ENOMEM */
634 nfs_direct_write_reschedule(dreq);
637 static void nfs_direct_write_clear_reqs(struct nfs_direct_req *dreq)
639 struct nfs_commit_info cinfo;
640 struct nfs_page *req;
643 nfs_init_cinfo_from_dreq(&cinfo, dreq);
644 nfs_direct_write_scan_commit_list(dreq->inode, &reqs, &cinfo);
646 while (!list_empty(&reqs)) {
647 req = nfs_list_entry(reqs.next);
648 nfs_list_remove_request(req);
649 nfs_release_request(req);
650 nfs_unlock_and_release_request(req);
654 static void nfs_direct_write_schedule_work(struct work_struct *work)
656 struct nfs_direct_req *dreq = container_of(work, struct nfs_direct_req, work);
657 int flags = dreq->flags;
661 case NFS_ODIRECT_DO_COMMIT:
662 nfs_direct_commit_schedule(dreq);
664 case NFS_ODIRECT_RESCHED_WRITES:
665 nfs_direct_write_reschedule(dreq);
668 nfs_direct_write_clear_reqs(dreq);
669 nfs_zap_mapping(dreq->inode, dreq->inode->i_mapping);
670 nfs_direct_complete(dreq);
674 static void nfs_direct_write_complete(struct nfs_direct_req *dreq)
676 trace_nfs_direct_write_complete(dreq);
677 queue_work(nfsiod_workqueue, &dreq->work); /* Calls nfs_direct_write_schedule_work */
680 static void nfs_direct_write_completion(struct nfs_pgio_header *hdr)
682 struct nfs_direct_req *dreq = hdr->dreq;
683 struct nfs_commit_info cinfo;
684 struct nfs_page *req = nfs_list_entry(hdr->pages.next);
685 int flags = NFS_ODIRECT_DONE;
687 trace_nfs_direct_write_completion(dreq);
689 nfs_init_cinfo_from_dreq(&cinfo, dreq);
691 spin_lock(&dreq->lock);
692 if (test_bit(NFS_IOHDR_REDO, &hdr->flags)) {
693 spin_unlock(&dreq->lock);
697 nfs_direct_count_bytes(dreq, hdr);
698 if (test_bit(NFS_IOHDR_UNSTABLE_WRITES, &hdr->flags)) {
700 dreq->flags = NFS_ODIRECT_DO_COMMIT;
703 spin_unlock(&dreq->lock);
705 while (!list_empty(&hdr->pages)) {
707 req = nfs_list_entry(hdr->pages.next);
708 nfs_list_remove_request(req);
709 if (flags == NFS_ODIRECT_DO_COMMIT) {
710 kref_get(&req->wb_kref);
711 memcpy(&req->wb_verf, &hdr->verf.verifier,
712 sizeof(req->wb_verf));
713 nfs_mark_request_commit(req, hdr->lseg, &cinfo,
715 } else if (flags == NFS_ODIRECT_RESCHED_WRITES) {
716 kref_get(&req->wb_kref);
717 nfs_mark_request_commit(req, NULL, &cinfo, 0);
719 nfs_unlock_and_release_request(req);
724 nfs_direct_write_complete(dreq);
728 static void nfs_write_sync_pgio_error(struct list_head *head, int error)
730 struct nfs_page *req;
732 while (!list_empty(head)) {
733 req = nfs_list_entry(head->next);
734 nfs_list_remove_request(req);
735 nfs_unlock_and_release_request(req);
739 static void nfs_direct_write_reschedule_io(struct nfs_pgio_header *hdr)
741 struct nfs_direct_req *dreq = hdr->dreq;
743 trace_nfs_direct_write_reschedule_io(dreq);
745 spin_lock(&dreq->lock);
746 if (dreq->error == 0) {
747 dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
748 /* fake unstable write to let common nfs resend pages */
749 hdr->verf.committed = NFS_UNSTABLE;
750 hdr->good_bytes = hdr->args.offset + hdr->args.count -
753 spin_unlock(&dreq->lock);
756 static const struct nfs_pgio_completion_ops nfs_direct_write_completion_ops = {
757 .error_cleanup = nfs_write_sync_pgio_error,
758 .init_hdr = nfs_direct_pgio_init,
759 .completion = nfs_direct_write_completion,
760 .reschedule_io = nfs_direct_write_reschedule_io,
765 * NB: Return the value of the first error return code. Subsequent
766 * errors after the first one are ignored.
769 * For each wsize'd chunk of the user's buffer, dispatch an NFS WRITE
770 * operation. If nfs_writedata_alloc() or get_user_pages() fails,
771 * bail and stop sending more writes. Write length accounting is
772 * handled automatically by nfs_direct_write_result(). Otherwise, if
773 * no requests have been sent, just return an error.
775 static ssize_t nfs_direct_write_schedule_iovec(struct nfs_direct_req *dreq,
776 struct iov_iter *iter,
777 loff_t pos, int ioflags)
779 struct nfs_pageio_descriptor desc;
780 struct inode *inode = dreq->inode;
782 size_t requested_bytes = 0;
783 size_t wsize = max_t(size_t, NFS_SERVER(inode)->wsize, PAGE_SIZE);
785 trace_nfs_direct_write_schedule_iovec(dreq);
787 nfs_pageio_init_write(&desc, inode, ioflags, false,
788 &nfs_direct_write_completion_ops);
791 inode_dio_begin(inode);
793 NFS_I(inode)->write_io += iov_iter_count(iter);
794 while (iov_iter_count(iter)) {
795 struct page **pagevec;
800 result = iov_iter_get_pages_alloc2(iter, &pagevec,
806 npages = (result + pgbase + PAGE_SIZE - 1) / PAGE_SIZE;
807 for (i = 0; i < npages; i++) {
808 struct nfs_page *req;
809 unsigned int req_len = min_t(size_t, bytes, PAGE_SIZE - pgbase);
811 req = nfs_create_request(dreq->ctx, pagevec[i],
814 result = PTR_ERR(req);
818 if (desc.pg_error < 0) {
819 nfs_free_request(req);
820 result = desc.pg_error;
824 nfs_lock_request(req);
825 req->wb_index = pos >> PAGE_SHIFT;
826 req->wb_offset = pos & ~PAGE_MASK;
827 if (!nfs_pageio_add_request(&desc, req)) {
828 result = desc.pg_error;
829 nfs_unlock_and_release_request(req);
834 requested_bytes += req_len;
836 dreq->bytes_left -= req_len;
838 nfs_direct_release_pages(pagevec, npages);
843 nfs_pageio_complete(&desc);
846 * If no bytes were started, return the error, and let the
847 * generic layer handle the completion.
849 if (requested_bytes == 0) {
850 inode_dio_end(inode);
851 nfs_direct_req_release(dreq);
852 return result < 0 ? result : -EIO;
856 nfs_direct_write_complete(dreq);
857 return requested_bytes;
861 * nfs_file_direct_write - file direct write operation for NFS files
862 * @iocb: target I/O control block
863 * @iter: vector of user buffers from which to write data
864 * @swap: flag indicating this is swap IO, not O_DIRECT IO
866 * We use this function for direct writes instead of calling
867 * generic_file_aio_write() in order to avoid taking the inode
868 * semaphore and updating the i_size. The NFS server will set
869 * the new i_size and this client must read the updated size
870 * back into its cache. We let the server do generic write
871 * parameter checking and report problems.
873 * We eliminate local atime updates, see direct read above.
875 * We avoid unnecessary page cache invalidations for normal cached
876 * readers of this file.
878 * Note that O_APPEND is not supported for NFS direct writes, as there
879 * is no atomic O_APPEND write facility in the NFS protocol.
881 ssize_t nfs_file_direct_write(struct kiocb *iocb, struct iov_iter *iter,
884 ssize_t result, requested;
886 struct file *file = iocb->ki_filp;
887 struct address_space *mapping = file->f_mapping;
888 struct inode *inode = mapping->host;
889 struct nfs_direct_req *dreq;
890 struct nfs_lock_context *l_ctx;
893 dfprintk(FILE, "NFS: direct write(%pD2, %zd@%Ld)\n",
894 file, iov_iter_count(iter), (long long) iocb->ki_pos);
897 /* bypass generic checks */
898 result = iov_iter_count(iter);
900 result = generic_write_checks(iocb, iter);
904 nfs_add_stats(mapping->host, NFSIOS_DIRECTWRITTENBYTES, count);
907 end = (pos + iov_iter_count(iter) - 1) >> PAGE_SHIFT;
909 task_io_account_write(count);
912 dreq = nfs_direct_req_alloc();
917 dreq->bytes_left = dreq->max_count = count;
918 dreq->io_start = pos;
919 dreq->ctx = get_nfs_open_context(nfs_file_open_context(iocb->ki_filp));
920 l_ctx = nfs_get_lock_context(dreq->ctx);
922 result = PTR_ERR(l_ctx);
923 nfs_direct_req_release(dreq);
927 if (!is_sync_kiocb(iocb))
929 pnfs_init_ds_commit_info_ops(&dreq->ds_cinfo, inode);
932 requested = nfs_direct_write_schedule_iovec(dreq, iter, pos,
935 nfs_start_io_direct(inode);
937 requested = nfs_direct_write_schedule_iovec(dreq, iter, pos,
940 if (mapping->nrpages) {
941 invalidate_inode_pages2_range(mapping,
942 pos >> PAGE_SHIFT, end);
945 nfs_end_io_direct(inode);
949 result = nfs_direct_wait(dreq);
952 iocb->ki_pos = pos + result;
953 /* XXX: should check the generic_write_sync retval */
954 generic_write_sync(iocb, result);
956 iov_iter_revert(iter, requested);
960 nfs_fscache_invalidate(inode, FSCACHE_INVAL_DIO_WRITE);
962 nfs_direct_req_release(dreq);
968 * nfs_init_directcache - create a slab cache for nfs_direct_req structures
971 int __init nfs_init_directcache(void)
973 nfs_direct_cachep = kmem_cache_create("nfs_direct_cache",
974 sizeof(struct nfs_direct_req),
975 0, (SLAB_RECLAIM_ACCOUNT|
978 if (nfs_direct_cachep == NULL)
985 * nfs_destroy_directcache - destroy the slab cache for nfs_direct_req structures
988 void nfs_destroy_directcache(void)
990 kmem_cache_destroy(nfs_direct_cachep);