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_page_create_from_page(dreq->ctx, pagevec[i],
347 pgbase, pos, req_len);
349 result = PTR_ERR(req);
352 if (!nfs_pageio_add_request(&desc, req)) {
353 result = desc.pg_error;
354 nfs_release_request(req);
359 requested_bytes += req_len;
361 dreq->bytes_left -= req_len;
363 nfs_direct_release_pages(pagevec, npages);
369 nfs_pageio_complete(&desc);
372 * If no bytes were started, return the error, and let the
373 * generic layer handle the completion.
375 if (requested_bytes == 0) {
376 inode_dio_end(inode);
377 nfs_direct_req_release(dreq);
378 return result < 0 ? result : -EIO;
382 nfs_direct_complete(dreq);
383 return requested_bytes;
387 * nfs_file_direct_read - file direct read operation for NFS files
388 * @iocb: target I/O control block
389 * @iter: vector of user buffers into which to read data
390 * @swap: flag indicating this is swap IO, not O_DIRECT IO
392 * We use this function for direct reads instead of calling
393 * generic_file_aio_read() in order to avoid gfar's check to see if
394 * the request starts before the end of the file. For that check
395 * to work, we must generate a GETATTR before each direct read, and
396 * even then there is a window between the GETATTR and the subsequent
397 * READ where the file size could change. Our preference is simply
398 * to do all reads the application wants, and the server will take
399 * care of managing the end of file boundary.
401 * This function also eliminates unnecessarily updating the file's
402 * atime locally, as the NFS server sets the file's atime, and this
403 * client must read the updated atime from the server back into its
406 ssize_t nfs_file_direct_read(struct kiocb *iocb, struct iov_iter *iter,
409 struct file *file = iocb->ki_filp;
410 struct address_space *mapping = file->f_mapping;
411 struct inode *inode = mapping->host;
412 struct nfs_direct_req *dreq;
413 struct nfs_lock_context *l_ctx;
414 ssize_t result, requested;
415 size_t count = iov_iter_count(iter);
416 nfs_add_stats(mapping->host, NFSIOS_DIRECTREADBYTES, count);
418 dfprintk(FILE, "NFS: direct read(%pD2, %zd@%Ld)\n",
419 file, count, (long long) iocb->ki_pos);
425 task_io_account_read(count);
428 dreq = nfs_direct_req_alloc();
433 dreq->bytes_left = dreq->max_count = count;
434 dreq->io_start = iocb->ki_pos;
435 dreq->ctx = get_nfs_open_context(nfs_file_open_context(iocb->ki_filp));
436 l_ctx = nfs_get_lock_context(dreq->ctx);
438 result = PTR_ERR(l_ctx);
439 nfs_direct_req_release(dreq);
443 if (!is_sync_kiocb(iocb))
446 if (user_backed_iter(iter))
447 dreq->flags = NFS_ODIRECT_SHOULD_DIRTY;
450 nfs_start_io_direct(inode);
452 NFS_I(inode)->read_io += count;
453 requested = nfs_direct_read_schedule_iovec(dreq, iter, iocb->ki_pos);
456 nfs_end_io_direct(inode);
459 result = nfs_direct_wait(dreq);
462 iocb->ki_pos += result;
464 iov_iter_revert(iter, requested);
470 nfs_direct_req_release(dreq);
475 static void nfs_direct_add_page_head(struct list_head *list,
476 struct nfs_page *req)
478 struct nfs_page *head = req->wb_head;
480 if (!list_empty(&head->wb_list) || !nfs_lock_request(head))
482 if (!list_empty(&head->wb_list)) {
483 nfs_unlock_request(head);
486 list_add(&head->wb_list, list);
487 kref_get(&head->wb_kref);
488 kref_get(&head->wb_kref);
491 static void nfs_direct_join_group(struct list_head *list, struct inode *inode)
493 struct nfs_page *req, *subreq;
495 list_for_each_entry(req, list, wb_list) {
496 if (req->wb_head != req) {
497 nfs_direct_add_page_head(&req->wb_list, req);
500 subreq = req->wb_this_page;
505 * Remove subrequests from this list before freeing
506 * them in the call to nfs_join_page_group().
508 if (!list_empty(&subreq->wb_list)) {
509 nfs_list_remove_request(subreq);
510 nfs_release_request(subreq);
512 } while ((subreq = subreq->wb_this_page) != req);
513 nfs_join_page_group(req, inode);
518 nfs_direct_write_scan_commit_list(struct inode *inode,
519 struct list_head *list,
520 struct nfs_commit_info *cinfo)
522 mutex_lock(&NFS_I(cinfo->inode)->commit_mutex);
523 pnfs_recover_commit_reqs(list, cinfo);
524 nfs_scan_commit_list(&cinfo->mds->list, list, cinfo, 0);
525 mutex_unlock(&NFS_I(cinfo->inode)->commit_mutex);
528 static void nfs_direct_write_reschedule(struct nfs_direct_req *dreq)
530 struct nfs_pageio_descriptor desc;
531 struct nfs_page *req, *tmp;
533 struct nfs_commit_info cinfo;
536 nfs_init_cinfo_from_dreq(&cinfo, dreq);
537 nfs_direct_write_scan_commit_list(dreq->inode, &reqs, &cinfo);
539 nfs_direct_join_group(&reqs, dreq->inode);
543 list_for_each_entry(req, &reqs, wb_list)
544 dreq->max_count += req->wb_bytes;
545 nfs_clear_pnfs_ds_commit_verifiers(&dreq->ds_cinfo);
548 nfs_pageio_init_write(&desc, dreq->inode, FLUSH_STABLE, false,
549 &nfs_direct_write_completion_ops);
552 list_for_each_entry_safe(req, tmp, &reqs, wb_list) {
553 /* Bump the transmission count */
555 if (!nfs_pageio_add_request(&desc, req)) {
556 nfs_list_move_request(req, &failed);
557 spin_lock(&cinfo.inode->i_lock);
559 if (desc.pg_error < 0)
560 dreq->error = desc.pg_error;
563 spin_unlock(&cinfo.inode->i_lock);
565 nfs_release_request(req);
567 nfs_pageio_complete(&desc);
569 while (!list_empty(&failed)) {
570 req = nfs_list_entry(failed.next);
571 nfs_list_remove_request(req);
572 nfs_unlock_and_release_request(req);
576 nfs_direct_write_complete(dreq);
579 static void nfs_direct_commit_complete(struct nfs_commit_data *data)
581 const struct nfs_writeverf *verf = data->res.verf;
582 struct nfs_direct_req *dreq = data->dreq;
583 struct nfs_commit_info cinfo;
584 struct nfs_page *req;
585 int status = data->task.tk_status;
587 trace_nfs_direct_commit_complete(dreq);
590 /* Errors in commit are fatal */
591 dreq->error = status;
594 dreq->flags = NFS_ODIRECT_DONE;
596 status = dreq->error;
599 nfs_init_cinfo_from_dreq(&cinfo, dreq);
601 while (!list_empty(&data->pages)) {
602 req = nfs_list_entry(data->pages.next);
603 nfs_list_remove_request(req);
604 if (status >= 0 && !nfs_write_match_verf(verf, req)) {
605 dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
607 * Despite the reboot, the write was successful,
611 nfs_mark_request_commit(req, NULL, &cinfo, 0);
612 } else /* Error or match */
613 nfs_release_request(req);
614 nfs_unlock_and_release_request(req);
617 if (nfs_commit_end(cinfo.mds))
618 nfs_direct_write_complete(dreq);
621 static void nfs_direct_resched_write(struct nfs_commit_info *cinfo,
622 struct nfs_page *req)
624 struct nfs_direct_req *dreq = cinfo->dreq;
626 trace_nfs_direct_resched_write(dreq);
628 spin_lock(&dreq->lock);
629 if (dreq->flags != NFS_ODIRECT_DONE)
630 dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
631 spin_unlock(&dreq->lock);
632 nfs_mark_request_commit(req, NULL, cinfo, 0);
635 static const struct nfs_commit_completion_ops nfs_direct_commit_completion_ops = {
636 .completion = nfs_direct_commit_complete,
637 .resched_write = nfs_direct_resched_write,
640 static void nfs_direct_commit_schedule(struct nfs_direct_req *dreq)
643 struct nfs_commit_info cinfo;
646 nfs_init_cinfo_from_dreq(&cinfo, dreq);
647 nfs_scan_commit(dreq->inode, &mds_list, &cinfo);
648 res = nfs_generic_commit_list(dreq->inode, &mds_list, 0, &cinfo);
649 if (res < 0) /* res == -ENOMEM */
650 nfs_direct_write_reschedule(dreq);
653 static void nfs_direct_write_clear_reqs(struct nfs_direct_req *dreq)
655 struct nfs_commit_info cinfo;
656 struct nfs_page *req;
659 nfs_init_cinfo_from_dreq(&cinfo, dreq);
660 nfs_direct_write_scan_commit_list(dreq->inode, &reqs, &cinfo);
662 while (!list_empty(&reqs)) {
663 req = nfs_list_entry(reqs.next);
664 nfs_list_remove_request(req);
665 nfs_release_request(req);
666 nfs_unlock_and_release_request(req);
670 static void nfs_direct_write_schedule_work(struct work_struct *work)
672 struct nfs_direct_req *dreq = container_of(work, struct nfs_direct_req, work);
673 int flags = dreq->flags;
677 case NFS_ODIRECT_DO_COMMIT:
678 nfs_direct_commit_schedule(dreq);
680 case NFS_ODIRECT_RESCHED_WRITES:
681 nfs_direct_write_reschedule(dreq);
684 nfs_direct_write_clear_reqs(dreq);
685 nfs_zap_mapping(dreq->inode, dreq->inode->i_mapping);
686 nfs_direct_complete(dreq);
690 static void nfs_direct_write_complete(struct nfs_direct_req *dreq)
692 trace_nfs_direct_write_complete(dreq);
693 queue_work(nfsiod_workqueue, &dreq->work); /* Calls nfs_direct_write_schedule_work */
696 static void nfs_direct_write_completion(struct nfs_pgio_header *hdr)
698 struct nfs_direct_req *dreq = hdr->dreq;
699 struct nfs_commit_info cinfo;
700 struct nfs_page *req = nfs_list_entry(hdr->pages.next);
701 int flags = NFS_ODIRECT_DONE;
703 trace_nfs_direct_write_completion(dreq);
705 nfs_init_cinfo_from_dreq(&cinfo, dreq);
707 spin_lock(&dreq->lock);
708 if (test_bit(NFS_IOHDR_REDO, &hdr->flags)) {
709 spin_unlock(&dreq->lock);
713 nfs_direct_count_bytes(dreq, hdr);
714 if (test_bit(NFS_IOHDR_UNSTABLE_WRITES, &hdr->flags)) {
716 dreq->flags = NFS_ODIRECT_DO_COMMIT;
719 spin_unlock(&dreq->lock);
721 while (!list_empty(&hdr->pages)) {
723 req = nfs_list_entry(hdr->pages.next);
724 nfs_list_remove_request(req);
725 if (flags == NFS_ODIRECT_DO_COMMIT) {
726 kref_get(&req->wb_kref);
727 memcpy(&req->wb_verf, &hdr->verf.verifier,
728 sizeof(req->wb_verf));
729 nfs_mark_request_commit(req, hdr->lseg, &cinfo,
731 } else if (flags == NFS_ODIRECT_RESCHED_WRITES) {
732 kref_get(&req->wb_kref);
733 nfs_mark_request_commit(req, NULL, &cinfo, 0);
735 nfs_unlock_and_release_request(req);
740 nfs_direct_write_complete(dreq);
744 static void nfs_write_sync_pgio_error(struct list_head *head, int error)
746 struct nfs_page *req;
748 while (!list_empty(head)) {
749 req = nfs_list_entry(head->next);
750 nfs_list_remove_request(req);
751 nfs_unlock_and_release_request(req);
755 static void nfs_direct_write_reschedule_io(struct nfs_pgio_header *hdr)
757 struct nfs_direct_req *dreq = hdr->dreq;
759 trace_nfs_direct_write_reschedule_io(dreq);
761 spin_lock(&dreq->lock);
762 if (dreq->error == 0) {
763 dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
764 /* fake unstable write to let common nfs resend pages */
765 hdr->verf.committed = NFS_UNSTABLE;
766 hdr->good_bytes = hdr->args.offset + hdr->args.count -
769 spin_unlock(&dreq->lock);
772 static const struct nfs_pgio_completion_ops nfs_direct_write_completion_ops = {
773 .error_cleanup = nfs_write_sync_pgio_error,
774 .init_hdr = nfs_direct_pgio_init,
775 .completion = nfs_direct_write_completion,
776 .reschedule_io = nfs_direct_write_reschedule_io,
781 * NB: Return the value of the first error return code. Subsequent
782 * errors after the first one are ignored.
785 * For each wsize'd chunk of the user's buffer, dispatch an NFS WRITE
786 * operation. If nfs_writedata_alloc() or get_user_pages() fails,
787 * bail and stop sending more writes. Write length accounting is
788 * handled automatically by nfs_direct_write_result(). Otherwise, if
789 * no requests have been sent, just return an error.
791 static ssize_t nfs_direct_write_schedule_iovec(struct nfs_direct_req *dreq,
792 struct iov_iter *iter,
793 loff_t pos, int ioflags)
795 struct nfs_pageio_descriptor desc;
796 struct inode *inode = dreq->inode;
798 size_t requested_bytes = 0;
799 size_t wsize = max_t(size_t, NFS_SERVER(inode)->wsize, PAGE_SIZE);
801 trace_nfs_direct_write_schedule_iovec(dreq);
803 nfs_pageio_init_write(&desc, inode, ioflags, false,
804 &nfs_direct_write_completion_ops);
807 inode_dio_begin(inode);
809 NFS_I(inode)->write_io += iov_iter_count(iter);
810 while (iov_iter_count(iter)) {
811 struct page **pagevec;
816 result = iov_iter_get_pages_alloc2(iter, &pagevec,
822 npages = (result + pgbase + PAGE_SIZE - 1) / PAGE_SIZE;
823 for (i = 0; i < npages; i++) {
824 struct nfs_page *req;
825 unsigned int req_len = min_t(size_t, bytes, PAGE_SIZE - pgbase);
827 req = nfs_page_create_from_page(dreq->ctx, pagevec[i],
828 pgbase, pos, req_len);
830 result = PTR_ERR(req);
834 if (desc.pg_error < 0) {
835 nfs_free_request(req);
836 result = desc.pg_error;
840 nfs_lock_request(req);
841 if (!nfs_pageio_add_request(&desc, req)) {
842 result = desc.pg_error;
843 nfs_unlock_and_release_request(req);
848 requested_bytes += req_len;
850 dreq->bytes_left -= req_len;
852 nfs_direct_release_pages(pagevec, npages);
857 nfs_pageio_complete(&desc);
860 * If no bytes were started, return the error, and let the
861 * generic layer handle the completion.
863 if (requested_bytes == 0) {
864 inode_dio_end(inode);
865 nfs_direct_req_release(dreq);
866 return result < 0 ? result : -EIO;
870 nfs_direct_write_complete(dreq);
871 return requested_bytes;
875 * nfs_file_direct_write - file direct write operation for NFS files
876 * @iocb: target I/O control block
877 * @iter: vector of user buffers from which to write data
878 * @swap: flag indicating this is swap IO, not O_DIRECT IO
880 * We use this function for direct writes instead of calling
881 * generic_file_aio_write() in order to avoid taking the inode
882 * semaphore and updating the i_size. The NFS server will set
883 * the new i_size and this client must read the updated size
884 * back into its cache. We let the server do generic write
885 * parameter checking and report problems.
887 * We eliminate local atime updates, see direct read above.
889 * We avoid unnecessary page cache invalidations for normal cached
890 * readers of this file.
892 * Note that O_APPEND is not supported for NFS direct writes, as there
893 * is no atomic O_APPEND write facility in the NFS protocol.
895 ssize_t nfs_file_direct_write(struct kiocb *iocb, struct iov_iter *iter,
898 ssize_t result, requested;
900 struct file *file = iocb->ki_filp;
901 struct address_space *mapping = file->f_mapping;
902 struct inode *inode = mapping->host;
903 struct nfs_direct_req *dreq;
904 struct nfs_lock_context *l_ctx;
907 dfprintk(FILE, "NFS: direct write(%pD2, %zd@%Ld)\n",
908 file, iov_iter_count(iter), (long long) iocb->ki_pos);
911 /* bypass generic checks */
912 result = iov_iter_count(iter);
914 result = generic_write_checks(iocb, iter);
918 nfs_add_stats(mapping->host, NFSIOS_DIRECTWRITTENBYTES, count);
921 end = (pos + iov_iter_count(iter) - 1) >> PAGE_SHIFT;
923 task_io_account_write(count);
926 dreq = nfs_direct_req_alloc();
931 dreq->bytes_left = dreq->max_count = count;
932 dreq->io_start = pos;
933 dreq->ctx = get_nfs_open_context(nfs_file_open_context(iocb->ki_filp));
934 l_ctx = nfs_get_lock_context(dreq->ctx);
936 result = PTR_ERR(l_ctx);
937 nfs_direct_req_release(dreq);
941 if (!is_sync_kiocb(iocb))
943 pnfs_init_ds_commit_info_ops(&dreq->ds_cinfo, inode);
946 requested = nfs_direct_write_schedule_iovec(dreq, iter, pos,
949 nfs_start_io_direct(inode);
951 requested = nfs_direct_write_schedule_iovec(dreq, iter, pos,
954 if (mapping->nrpages) {
955 invalidate_inode_pages2_range(mapping,
956 pos >> PAGE_SHIFT, end);
959 nfs_end_io_direct(inode);
963 result = nfs_direct_wait(dreq);
966 iocb->ki_pos = pos + result;
967 /* XXX: should check the generic_write_sync retval */
968 generic_write_sync(iocb, result);
970 iov_iter_revert(iter, requested);
974 nfs_fscache_invalidate(inode, FSCACHE_INVAL_DIO_WRITE);
976 nfs_direct_req_release(dreq);
982 * nfs_init_directcache - create a slab cache for nfs_direct_req structures
985 int __init nfs_init_directcache(void)
987 nfs_direct_cachep = kmem_cache_create("nfs_direct_cache",
988 sizeof(struct nfs_direct_req),
989 0, (SLAB_RECLAIM_ACCOUNT|
992 if (nfs_direct_cachep == NULL)
999 * nfs_destroy_directcache - destroy the slab cache for nfs_direct_req structures
1002 void nfs_destroy_directcache(void)
1004 kmem_cache_destroy(nfs_direct_cachep);