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, const struct iovec *iov, loff_t pos, unsigned long nr_segs)
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, 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, iov, nr_segs, pos,
136 rw == READ ? true : false);
137 return nfs_file_direct_write(iocb, iov, nr_segs, 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 nfs_free_pnfs_ds_cinfo(&dreq->ds_cinfo);
182 if (dreq->l_ctx != NULL)
183 nfs_put_lock_context(dreq->l_ctx);
184 if (dreq->ctx != NULL)
185 put_nfs_open_context(dreq->ctx);
186 kmem_cache_free(nfs_direct_cachep, dreq);
189 static void nfs_direct_req_release(struct nfs_direct_req *dreq)
191 kref_put(&dreq->kref, nfs_direct_req_free);
194 ssize_t nfs_dreq_bytes_left(struct nfs_direct_req *dreq)
196 return dreq->bytes_left;
198 EXPORT_SYMBOL_GPL(nfs_dreq_bytes_left);
201 * Collects and returns the final error value/byte-count.
203 static ssize_t nfs_direct_wait(struct nfs_direct_req *dreq)
205 ssize_t result = -EIOCBQUEUED;
207 /* Async requests don't wait here */
211 result = wait_for_completion_killable(&dreq->completion);
214 result = dreq->error;
216 result = dreq->count;
219 return (ssize_t) result;
223 * Synchronous I/O uses a stack-allocated iocb. Thus we can't trust
224 * the iocb is still valid here if this is a synchronous request.
226 static void nfs_direct_complete(struct nfs_direct_req *dreq, bool write)
228 struct inode *inode = dreq->inode;
230 if (dreq->iocb && write) {
231 loff_t pos = dreq->iocb->ki_pos + dreq->count;
233 spin_lock(&inode->i_lock);
234 if (i_size_read(inode) < pos)
235 i_size_write(inode, pos);
236 spin_unlock(&inode->i_lock);
240 nfs_zap_mapping(inode, inode->i_mapping);
242 inode_dio_done(inode);
245 long res = (long) dreq->error;
247 res = (long) dreq->count;
248 aio_complete(dreq->iocb, res, 0);
251 complete_all(&dreq->completion);
253 nfs_direct_req_release(dreq);
256 static void nfs_direct_readpage_release(struct nfs_page *req)
258 dprintk("NFS: direct read done (%s/%llu %d@%lld)\n",
259 req->wb_context->dentry->d_inode->i_sb->s_id,
260 (unsigned long long)NFS_FILEID(req->wb_context->dentry->d_inode),
262 (long long)req_offset(req));
263 nfs_release_request(req);
266 static void nfs_direct_read_completion(struct nfs_pgio_header *hdr)
268 unsigned long bytes = 0;
269 struct nfs_direct_req *dreq = hdr->dreq;
271 if (test_bit(NFS_IOHDR_REDO, &hdr->flags))
274 spin_lock(&dreq->lock);
275 if (test_bit(NFS_IOHDR_ERROR, &hdr->flags) && (hdr->good_bytes == 0))
276 dreq->error = hdr->error;
278 dreq->count += hdr->good_bytes;
279 spin_unlock(&dreq->lock);
281 while (!list_empty(&hdr->pages)) {
282 struct nfs_page *req = nfs_list_entry(hdr->pages.next);
283 struct page *page = req->wb_page;
285 if (!PageCompound(page) && bytes < hdr->good_bytes)
286 set_page_dirty(page);
287 bytes += req->wb_bytes;
288 nfs_list_remove_request(req);
289 nfs_direct_readpage_release(req);
293 nfs_direct_complete(dreq, false);
297 static void nfs_read_sync_pgio_error(struct list_head *head)
299 struct nfs_page *req;
301 while (!list_empty(head)) {
302 req = nfs_list_entry(head->next);
303 nfs_list_remove_request(req);
304 nfs_release_request(req);
308 static void nfs_direct_pgio_init(struct nfs_pgio_header *hdr)
313 static const struct nfs_pgio_completion_ops nfs_direct_read_completion_ops = {
314 .error_cleanup = nfs_read_sync_pgio_error,
315 .init_hdr = nfs_direct_pgio_init,
316 .completion = nfs_direct_read_completion,
320 * For each rsize'd chunk of the user's buffer, dispatch an NFS READ
321 * operation. If nfs_readdata_alloc() or get_user_pages() fails,
322 * bail and stop sending more reads. Read length accounting is
323 * handled automatically by nfs_direct_read_result(). Otherwise, if
324 * no requests have been sent, just return an error.
326 static ssize_t nfs_direct_read_schedule_segment(struct nfs_pageio_descriptor *desc,
327 const struct iovec *iov,
328 loff_t pos, bool uio)
330 struct nfs_direct_req *dreq = desc->pg_dreq;
331 struct nfs_open_context *ctx = dreq->ctx;
332 struct inode *inode = ctx->dentry->d_inode;
333 unsigned long user_addr = (unsigned long)iov->iov_base;
334 size_t count = iov->iov_len;
335 size_t rsize = NFS_SERVER(inode)->rsize;
339 struct page **pagevec = NULL;
346 pgbase = user_addr & ~PAGE_MASK;
347 bytes = min(max_t(size_t, rsize, PAGE_SIZE), count);
350 npages = nfs_page_array_len(pgbase, bytes);
352 pagevec = kmalloc(npages * sizeof(struct page *),
357 down_read(¤t->mm->mmap_sem);
358 result = get_user_pages(current, current->mm, user_addr,
359 npages, 1, 0, pagevec, NULL);
360 up_read(¤t->mm->mmap_sem);
364 WARN_ON(npages != 1);
365 result = get_kernel_page(user_addr, 1, pagevec);
366 if (WARN_ON(result != 1))
370 if ((unsigned)result < npages) {
371 bytes = result * PAGE_SIZE;
372 if (bytes <= pgbase) {
373 nfs_direct_release_pages(pagevec, result);
380 for (i = 0; i < npages; i++) {
381 struct nfs_page *req;
382 unsigned int req_len = min_t(size_t, bytes, PAGE_SIZE - pgbase);
383 /* XXX do we need to do the eof zeroing found in async_filler? */
384 req = nfs_create_request(dreq->ctx, dreq->inode,
388 result = PTR_ERR(req);
391 req->wb_index = pos >> PAGE_SHIFT;
392 req->wb_offset = pos & ~PAGE_MASK;
393 if (!nfs_pageio_add_request(desc, req)) {
394 result = desc->pg_error;
395 nfs_release_request(req);
401 user_addr += req_len;
404 dreq->bytes_left -= req_len;
406 /* The nfs_page now hold references to these pages */
407 nfs_direct_release_pages(pagevec, npages);
408 } while (count != 0 && result >= 0);
414 return result < 0 ? (ssize_t) result : -EFAULT;
417 static ssize_t nfs_direct_read_schedule_iovec(struct nfs_direct_req *dreq,
418 const struct iovec *iov,
419 unsigned long nr_segs,
420 loff_t pos, bool uio)
422 struct nfs_pageio_descriptor desc;
423 struct inode *inode = dreq->inode;
424 ssize_t result = -EINVAL;
425 size_t requested_bytes = 0;
428 NFS_PROTO(dreq->inode)->read_pageio_init(&desc, dreq->inode,
429 &nfs_direct_read_completion_ops);
432 atomic_inc(&inode->i_dio_count);
434 for (seg = 0; seg < nr_segs; seg++) {
435 const struct iovec *vec = &iov[seg];
436 result = nfs_direct_read_schedule_segment(&desc, vec, pos, uio);
439 requested_bytes += result;
440 if ((size_t)result < vec->iov_len)
445 nfs_pageio_complete(&desc);
448 * If no bytes were started, return the error, and let the
449 * generic layer handle the completion.
451 if (requested_bytes == 0) {
452 inode_dio_done(inode);
453 nfs_direct_req_release(dreq);
454 return result < 0 ? result : -EIO;
458 nfs_direct_complete(dreq, false);
463 * nfs_file_direct_read - file direct read operation for NFS files
464 * @iocb: target I/O control block
465 * @iov: vector of user buffers into which to read data
466 * @nr_segs: size of iov vector
467 * @pos: byte offset in file where reading starts
469 * We use this function for direct reads instead of calling
470 * generic_file_aio_read() in order to avoid gfar's check to see if
471 * the request starts before the end of the file. For that check
472 * to work, we must generate a GETATTR before each direct read, and
473 * even then there is a window between the GETATTR and the subsequent
474 * READ where the file size could change. Our preference is simply
475 * to do all reads the application wants, and the server will take
476 * care of managing the end of file boundary.
478 * This function also eliminates unnecessarily updating the file's
479 * atime locally, as the NFS server sets the file's atime, and this
480 * client must read the updated atime from the server back into its
483 ssize_t nfs_file_direct_read(struct kiocb *iocb, const struct iovec *iov,
484 unsigned long nr_segs, loff_t pos, bool uio)
486 struct file *file = iocb->ki_filp;
487 struct address_space *mapping = file->f_mapping;
488 struct inode *inode = mapping->host;
489 struct nfs_direct_req *dreq;
490 struct nfs_lock_context *l_ctx;
491 ssize_t result = -EINVAL;
494 count = iov_length(iov, nr_segs);
495 nfs_add_stats(mapping->host, NFSIOS_DIRECTREADBYTES, count);
497 dfprintk(FILE, "NFS: direct read(%pD2, %zd@%Ld)\n",
498 file, count, (long long) pos);
504 mutex_lock(&inode->i_mutex);
505 result = nfs_sync_mapping(mapping);
509 task_io_account_read(count);
512 dreq = nfs_direct_req_alloc();
517 dreq->bytes_left = iov_length(iov, nr_segs);
518 dreq->ctx = get_nfs_open_context(nfs_file_open_context(iocb->ki_filp));
519 l_ctx = nfs_get_lock_context(dreq->ctx);
521 result = PTR_ERR(l_ctx);
525 if (!is_sync_kiocb(iocb))
528 NFS_I(inode)->read_io += iov_length(iov, nr_segs);
529 result = nfs_direct_read_schedule_iovec(dreq, iov, nr_segs, pos, uio);
531 mutex_unlock(&inode->i_mutex);
534 result = nfs_direct_wait(dreq);
536 iocb->ki_pos = pos + result;
539 nfs_direct_req_release(dreq);
543 nfs_direct_req_release(dreq);
545 mutex_unlock(&inode->i_mutex);
550 #if IS_ENABLED(CONFIG_NFS_V3) || IS_ENABLED(CONFIG_NFS_V4)
551 static void nfs_direct_write_reschedule(struct nfs_direct_req *dreq)
553 struct nfs_pageio_descriptor desc;
554 struct nfs_page *req, *tmp;
556 struct nfs_commit_info cinfo;
559 nfs_init_cinfo_from_dreq(&cinfo, dreq);
560 pnfs_recover_commit_reqs(dreq->inode, &reqs, &cinfo);
561 spin_lock(cinfo.lock);
562 nfs_scan_commit_list(&cinfo.mds->list, &reqs, &cinfo, 0);
563 spin_unlock(cinfo.lock);
568 NFS_PROTO(dreq->inode)->write_pageio_init(&desc, dreq->inode, FLUSH_STABLE,
569 &nfs_direct_write_completion_ops);
572 list_for_each_entry_safe(req, tmp, &reqs, wb_list) {
573 if (!nfs_pageio_add_request(&desc, req)) {
574 nfs_list_remove_request(req);
575 nfs_list_add_request(req, &failed);
576 spin_lock(cinfo.lock);
579 spin_unlock(cinfo.lock);
581 nfs_release_request(req);
583 nfs_pageio_complete(&desc);
585 while (!list_empty(&failed)) {
586 req = nfs_list_entry(failed.next);
587 nfs_list_remove_request(req);
588 nfs_unlock_and_release_request(req);
592 nfs_direct_write_complete(dreq, dreq->inode);
595 static void nfs_direct_commit_complete(struct nfs_commit_data *data)
597 struct nfs_direct_req *dreq = data->dreq;
598 struct nfs_commit_info cinfo;
599 struct nfs_page *req;
600 int status = data->task.tk_status;
602 nfs_init_cinfo_from_dreq(&cinfo, dreq);
604 dprintk("NFS: %5u commit failed with error %d.\n",
605 data->task.tk_pid, status);
606 dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
607 } else if (memcmp(&dreq->verf, &data->verf, sizeof(data->verf))) {
608 dprintk("NFS: %5u commit verify failed\n", data->task.tk_pid);
609 dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
612 dprintk("NFS: %5u commit returned %d\n", data->task.tk_pid, status);
613 while (!list_empty(&data->pages)) {
614 req = nfs_list_entry(data->pages.next);
615 nfs_list_remove_request(req);
616 if (dreq->flags == NFS_ODIRECT_RESCHED_WRITES) {
617 /* Note the rewrite will go through mds */
618 nfs_mark_request_commit(req, NULL, &cinfo);
620 nfs_release_request(req);
621 nfs_unlock_and_release_request(req);
624 if (atomic_dec_and_test(&cinfo.mds->rpcs_out))
625 nfs_direct_write_complete(dreq, data->inode);
628 static void nfs_direct_error_cleanup(struct nfs_inode *nfsi)
630 /* There is no lock to clear */
633 static const struct nfs_commit_completion_ops nfs_direct_commit_completion_ops = {
634 .completion = nfs_direct_commit_complete,
635 .error_cleanup = nfs_direct_error_cleanup,
638 static void nfs_direct_commit_schedule(struct nfs_direct_req *dreq)
641 struct nfs_commit_info cinfo;
644 nfs_init_cinfo_from_dreq(&cinfo, dreq);
645 nfs_scan_commit(dreq->inode, &mds_list, &cinfo);
646 res = nfs_generic_commit_list(dreq->inode, &mds_list, 0, &cinfo);
647 if (res < 0) /* res == -ENOMEM */
648 nfs_direct_write_reschedule(dreq);
651 static void nfs_direct_write_schedule_work(struct work_struct *work)
653 struct nfs_direct_req *dreq = container_of(work, struct nfs_direct_req, work);
654 int flags = dreq->flags;
658 case NFS_ODIRECT_DO_COMMIT:
659 nfs_direct_commit_schedule(dreq);
661 case NFS_ODIRECT_RESCHED_WRITES:
662 nfs_direct_write_reschedule(dreq);
665 nfs_direct_complete(dreq, true);
669 static void nfs_direct_write_complete(struct nfs_direct_req *dreq, struct inode *inode)
671 schedule_work(&dreq->work); /* Calls nfs_direct_write_schedule_work */
675 static void nfs_direct_write_schedule_work(struct work_struct *work)
679 static void nfs_direct_write_complete(struct nfs_direct_req *dreq, struct inode *inode)
681 nfs_direct_complete(dreq, true);
686 * NB: Return the value of the first error return code. Subsequent
687 * errors after the first one are ignored.
690 * For each wsize'd chunk of the user's buffer, dispatch an NFS WRITE
691 * operation. If nfs_writedata_alloc() or get_user_pages() fails,
692 * bail and stop sending more writes. Write length accounting is
693 * handled automatically by nfs_direct_write_result(). Otherwise, if
694 * no requests have been sent, just return an error.
696 static ssize_t nfs_direct_write_schedule_segment(struct nfs_pageio_descriptor *desc,
697 const struct iovec *iov,
698 loff_t pos, bool uio)
700 struct nfs_direct_req *dreq = desc->pg_dreq;
701 struct nfs_open_context *ctx = dreq->ctx;
702 struct inode *inode = ctx->dentry->d_inode;
703 unsigned long user_addr = (unsigned long)iov->iov_base;
704 size_t count = iov->iov_len;
705 size_t wsize = NFS_SERVER(inode)->wsize;
709 struct page **pagevec = NULL;
716 pgbase = user_addr & ~PAGE_MASK;
717 bytes = min(max_t(size_t, wsize, PAGE_SIZE), count);
720 npages = nfs_page_array_len(pgbase, bytes);
722 pagevec = kmalloc(npages * sizeof(struct page *), GFP_KERNEL);
727 down_read(¤t->mm->mmap_sem);
728 result = get_user_pages(current, current->mm, user_addr,
729 npages, 0, 0, pagevec, NULL);
730 up_read(¤t->mm->mmap_sem);
734 WARN_ON(npages != 1);
735 result = get_kernel_page(user_addr, 0, pagevec);
736 if (WARN_ON(result != 1))
740 if ((unsigned)result < npages) {
741 bytes = result * PAGE_SIZE;
742 if (bytes <= pgbase) {
743 nfs_direct_release_pages(pagevec, result);
750 for (i = 0; i < npages; i++) {
751 struct nfs_page *req;
752 unsigned int req_len = min_t(size_t, bytes, PAGE_SIZE - pgbase);
754 req = nfs_create_request(dreq->ctx, dreq->inode,
758 result = PTR_ERR(req);
761 nfs_lock_request(req);
762 req->wb_index = pos >> PAGE_SHIFT;
763 req->wb_offset = pos & ~PAGE_MASK;
764 if (!nfs_pageio_add_request(desc, req)) {
765 result = desc->pg_error;
766 nfs_unlock_and_release_request(req);
772 user_addr += req_len;
775 dreq->bytes_left -= req_len;
777 /* The nfs_page now hold references to these pages */
778 nfs_direct_release_pages(pagevec, npages);
779 } while (count != 0 && result >= 0);
785 return result < 0 ? (ssize_t) result : -EFAULT;
788 static void nfs_direct_write_completion(struct nfs_pgio_header *hdr)
790 struct nfs_direct_req *dreq = hdr->dreq;
791 struct nfs_commit_info cinfo;
793 struct nfs_page *req = nfs_list_entry(hdr->pages.next);
795 if (test_bit(NFS_IOHDR_REDO, &hdr->flags))
798 nfs_init_cinfo_from_dreq(&cinfo, dreq);
800 spin_lock(&dreq->lock);
802 if (test_bit(NFS_IOHDR_ERROR, &hdr->flags)) {
804 dreq->error = hdr->error;
806 if (dreq->error != 0)
807 bit = NFS_IOHDR_ERROR;
809 dreq->count += hdr->good_bytes;
810 if (test_bit(NFS_IOHDR_NEED_RESCHED, &hdr->flags)) {
811 dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
812 bit = NFS_IOHDR_NEED_RESCHED;
813 } else if (test_bit(NFS_IOHDR_NEED_COMMIT, &hdr->flags)) {
814 if (dreq->flags == NFS_ODIRECT_RESCHED_WRITES)
815 bit = NFS_IOHDR_NEED_RESCHED;
816 else if (dreq->flags == 0) {
817 memcpy(&dreq->verf, hdr->verf,
819 bit = NFS_IOHDR_NEED_COMMIT;
820 dreq->flags = NFS_ODIRECT_DO_COMMIT;
821 } else if (dreq->flags == NFS_ODIRECT_DO_COMMIT) {
822 if (memcmp(&dreq->verf, hdr->verf, sizeof(dreq->verf))) {
823 dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
824 bit = NFS_IOHDR_NEED_RESCHED;
826 bit = NFS_IOHDR_NEED_COMMIT;
830 spin_unlock(&dreq->lock);
832 while (!list_empty(&hdr->pages)) {
833 req = nfs_list_entry(hdr->pages.next);
834 nfs_list_remove_request(req);
836 case NFS_IOHDR_NEED_RESCHED:
837 case NFS_IOHDR_NEED_COMMIT:
838 kref_get(&req->wb_kref);
839 nfs_mark_request_commit(req, hdr->lseg, &cinfo);
841 nfs_unlock_and_release_request(req);
846 nfs_direct_write_complete(dreq, hdr->inode);
850 static void nfs_write_sync_pgio_error(struct list_head *head)
852 struct nfs_page *req;
854 while (!list_empty(head)) {
855 req = nfs_list_entry(head->next);
856 nfs_list_remove_request(req);
857 nfs_unlock_and_release_request(req);
861 static const struct nfs_pgio_completion_ops nfs_direct_write_completion_ops = {
862 .error_cleanup = nfs_write_sync_pgio_error,
863 .init_hdr = nfs_direct_pgio_init,
864 .completion = nfs_direct_write_completion,
867 static ssize_t nfs_direct_write_schedule_iovec(struct nfs_direct_req *dreq,
868 const struct iovec *iov,
869 unsigned long nr_segs,
870 loff_t pos, bool uio)
872 struct nfs_pageio_descriptor desc;
873 struct inode *inode = dreq->inode;
875 size_t requested_bytes = 0;
878 NFS_PROTO(inode)->write_pageio_init(&desc, inode, FLUSH_COND_STABLE,
879 &nfs_direct_write_completion_ops);
882 atomic_inc(&inode->i_dio_count);
884 NFS_I(dreq->inode)->write_io += iov_length(iov, nr_segs);
885 for (seg = 0; seg < nr_segs; seg++) {
886 const struct iovec *vec = &iov[seg];
887 result = nfs_direct_write_schedule_segment(&desc, vec, pos, uio);
890 requested_bytes += result;
891 if ((size_t)result < vec->iov_len)
895 nfs_pageio_complete(&desc);
898 * If no bytes were started, return the error, and let the
899 * generic layer handle the completion.
901 if (requested_bytes == 0) {
902 inode_dio_done(inode);
903 nfs_direct_req_release(dreq);
904 return result < 0 ? result : -EIO;
908 nfs_direct_write_complete(dreq, dreq->inode);
913 * nfs_file_direct_write - file direct write operation for NFS files
914 * @iocb: target I/O control block
915 * @iov: vector of user buffers from which to write data
916 * @nr_segs: size of iov vector
917 * @pos: byte offset in file where writing starts
919 * We use this function for direct writes instead of calling
920 * generic_file_aio_write() in order to avoid taking the inode
921 * semaphore and updating the i_size. The NFS server will set
922 * the new i_size and this client must read the updated size
923 * back into its cache. We let the server do generic write
924 * parameter checking and report problems.
926 * We eliminate local atime updates, see direct read above.
928 * We avoid unnecessary page cache invalidations for normal cached
929 * readers of this file.
931 * Note that O_APPEND is not supported for NFS direct writes, as there
932 * is no atomic O_APPEND write facility in the NFS protocol.
934 ssize_t nfs_file_direct_write(struct kiocb *iocb, const struct iovec *iov,
935 unsigned long nr_segs, loff_t pos, bool uio)
937 ssize_t result = -EINVAL;
938 struct file *file = iocb->ki_filp;
939 struct address_space *mapping = file->f_mapping;
940 struct inode *inode = mapping->host;
941 struct nfs_direct_req *dreq;
942 struct nfs_lock_context *l_ctx;
946 count = iov_length(iov, nr_segs);
947 end = (pos + count - 1) >> PAGE_CACHE_SHIFT;
949 nfs_add_stats(mapping->host, NFSIOS_DIRECTWRITTENBYTES, count);
951 dfprintk(FILE, "NFS: direct write(%pD2, %zd@%Ld)\n",
952 file, count, (long long) pos);
954 result = generic_write_checks(file, &pos, &count, 0);
959 if ((ssize_t) count < 0)
965 mutex_lock(&inode->i_mutex);
967 result = nfs_sync_mapping(mapping);
971 if (mapping->nrpages) {
972 result = invalidate_inode_pages2_range(mapping,
973 pos >> PAGE_CACHE_SHIFT, end);
978 task_io_account_write(count);
981 dreq = nfs_direct_req_alloc();
986 dreq->bytes_left = count;
987 dreq->ctx = get_nfs_open_context(nfs_file_open_context(iocb->ki_filp));
988 l_ctx = nfs_get_lock_context(dreq->ctx);
990 result = PTR_ERR(l_ctx);
994 if (!is_sync_kiocb(iocb))
997 result = nfs_direct_write_schedule_iovec(dreq, iov, nr_segs, pos, uio);
999 if (mapping->nrpages) {
1000 invalidate_inode_pages2_range(mapping,
1001 pos >> PAGE_CACHE_SHIFT, end);
1004 mutex_unlock(&inode->i_mutex);
1007 result = nfs_direct_wait(dreq);
1009 struct inode *inode = mapping->host;
1011 iocb->ki_pos = pos + result;
1012 spin_lock(&inode->i_lock);
1013 if (i_size_read(inode) < iocb->ki_pos)
1014 i_size_write(inode, iocb->ki_pos);
1015 spin_unlock(&inode->i_lock);
1018 nfs_direct_req_release(dreq);
1022 nfs_direct_req_release(dreq);
1024 mutex_unlock(&inode->i_mutex);
1030 * nfs_init_directcache - create a slab cache for nfs_direct_req structures
1033 int __init nfs_init_directcache(void)
1035 nfs_direct_cachep = kmem_cache_create("nfs_direct_cache",
1036 sizeof(struct nfs_direct_req),
1037 0, (SLAB_RECLAIM_ACCOUNT|
1040 if (nfs_direct_cachep == NULL)
1047 * nfs_destroy_directcache - destroy the slab cache for nfs_direct_req structures
1050 void nfs_destroy_directcache(void)
1052 kmem_cache_destroy(nfs_direct_cachep);