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/config.h>
42 #include <linux/errno.h>
43 #include <linux/sched.h>
44 #include <linux/kernel.h>
45 #include <linux/smp_lock.h>
46 #include <linux/file.h>
47 #include <linux/pagemap.h>
48 #include <linux/kref.h>
50 #include <linux/nfs_fs.h>
51 #include <linux/nfs_page.h>
52 #include <linux/sunrpc/clnt.h>
54 #include <asm/system.h>
55 #include <asm/uaccess.h>
56 #include <asm/atomic.h>
60 #define NFSDBG_FACILITY NFSDBG_VFS
62 static void nfs_free_user_pages(struct page **pages, int npages, int do_dirty);
63 static kmem_cache_t *nfs_direct_cachep;
66 * This represents a set of asynchronous requests that we're waiting on
68 struct nfs_direct_req {
69 struct kref kref; /* release manager */
72 struct list_head list; /* nfs_read/write_data structs */
73 struct file * filp; /* file descriptor */
74 struct kiocb * iocb; /* controlling i/o request */
75 wait_queue_head_t wait; /* wait for i/o completion */
76 struct inode * inode; /* target file of i/o */
77 struct page ** pages; /* pages in our buffer */
78 unsigned int npages; /* count of pages */
80 /* completion state */
81 spinlock_t lock; /* protect completion state */
82 int outstanding; /* i/os we're waiting for */
83 ssize_t count, /* bytes actually processed */
84 error; /* any reported error */
88 * nfs_direct_IO - NFS address space operation for direct I/O
89 * @rw: direction (read or write)
90 * @iocb: target I/O control block
91 * @iov: array of vectors that define I/O buffer
92 * @pos: offset in file to begin the operation
93 * @nr_segs: size of iovec array
95 * The presence of this routine in the address space ops vector means
96 * the NFS client supports direct I/O. However, we shunt off direct
97 * read and write requests before the VFS gets them, so this method
98 * should never be called.
100 ssize_t nfs_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov, loff_t pos, unsigned long nr_segs)
102 struct dentry *dentry = iocb->ki_filp->f_dentry;
104 dprintk("NFS: nfs_direct_IO (%s) off/no(%Ld/%lu) EINVAL\n",
105 dentry->d_name.name, (long long) pos, nr_segs);
110 static inline int nfs_get_user_pages(int rw, unsigned long user_addr, size_t size, struct page ***pages)
112 int result = -ENOMEM;
113 unsigned long page_count;
116 page_count = (user_addr + size + PAGE_SIZE - 1) >> PAGE_SHIFT;
117 page_count -= user_addr >> PAGE_SHIFT;
119 array_size = (page_count * sizeof(struct page *));
120 *pages = kmalloc(array_size, GFP_KERNEL);
122 down_read(¤t->mm->mmap_sem);
123 result = get_user_pages(current, current->mm, user_addr,
124 page_count, (rw == READ), 0,
126 up_read(¤t->mm->mmap_sem);
128 * If we got fewer pages than expected from get_user_pages(),
129 * the user buffer runs off the end of a mapping; return EFAULT.
131 if (result >= 0 && result < page_count) {
132 nfs_free_user_pages(*pages, result, 0);
140 static void nfs_free_user_pages(struct page **pages, int npages, int do_dirty)
143 for (i = 0; i < npages; i++) {
144 struct page *page = pages[i];
145 if (do_dirty && !PageCompound(page))
146 set_page_dirty_lock(page);
147 page_cache_release(page);
152 static inline struct nfs_direct_req *nfs_direct_req_alloc(void)
154 struct nfs_direct_req *dreq;
156 dreq = kmem_cache_alloc(nfs_direct_cachep, SLAB_KERNEL);
160 kref_init(&dreq->kref);
161 init_waitqueue_head(&dreq->wait);
162 INIT_LIST_HEAD(&dreq->list);
164 spin_lock_init(&dreq->lock);
165 dreq->outstanding = 0;
172 static void nfs_direct_req_release(struct kref *kref)
174 struct nfs_direct_req *dreq = container_of(kref, struct nfs_direct_req, kref);
175 kmem_cache_free(nfs_direct_cachep, dreq);
179 * Collects and returns the final error value/byte-count.
181 static ssize_t nfs_direct_wait(struct nfs_direct_req *dreq)
183 ssize_t result = -EIOCBQUEUED;
185 /* Async requests don't wait here */
189 result = wait_event_interruptible(dreq->wait, (dreq->outstanding == 0));
192 result = dreq->error;
194 result = dreq->count;
197 kref_put(&dreq->kref, nfs_direct_req_release);
198 return (ssize_t) result;
202 * We must hold a reference to all the pages in this direct read request
203 * until the RPCs complete. This could be long *after* we are woken up in
204 * nfs_direct_wait (for instance, if someone hits ^C on a slow server).
206 * In addition, synchronous I/O uses a stack-allocated iocb. Thus we
207 * can't trust the iocb is still valid here if this is a synchronous
208 * request. If the waiter is woken prematurely, the iocb is long gone.
210 static void nfs_direct_complete(struct nfs_direct_req *dreq)
212 nfs_free_user_pages(dreq->pages, dreq->npages, 1);
215 long res = (long) dreq->error;
217 res = (long) dreq->count;
218 aio_complete(dreq->iocb, res, 0);
220 wake_up(&dreq->wait);
222 kref_put(&dreq->kref, nfs_direct_req_release);
226 * Note we also set the number of requests we have in the dreq when we are
227 * done. This prevents races with I/O completion so we will always wait
228 * until all requests have been dispatched and completed.
230 static struct nfs_direct_req *nfs_direct_read_alloc(size_t nbytes, size_t rsize)
232 struct list_head *list;
233 struct nfs_direct_req *dreq;
234 unsigned int rpages = (rsize + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
236 dreq = nfs_direct_req_alloc();
242 struct nfs_read_data *data = nfs_readdata_alloc(rpages);
244 if (unlikely(!data)) {
245 while (!list_empty(list)) {
246 data = list_entry(list->next,
247 struct nfs_read_data, pages);
248 list_del(&data->pages);
249 nfs_readdata_free(data);
251 kref_put(&dreq->kref, nfs_direct_req_release);
255 INIT_LIST_HEAD(&data->pages);
256 list_add(&data->pages, list);
258 data->req = (struct nfs_page *) dreq;
264 kref_get(&dreq->kref);
268 static void nfs_direct_read_result(struct rpc_task *task, void *calldata)
270 struct nfs_read_data *data = calldata;
271 struct nfs_direct_req *dreq = (struct nfs_direct_req *) data->req;
273 if (nfs_readpage_result(task, data) != 0)
276 spin_lock(&dreq->lock);
278 if (likely(task->tk_status >= 0))
279 dreq->count += data->res.count;
281 dreq->error = task->tk_status;
283 if (--dreq->outstanding) {
284 spin_unlock(&dreq->lock);
288 spin_unlock(&dreq->lock);
289 nfs_direct_complete(dreq);
292 static const struct rpc_call_ops nfs_read_direct_ops = {
293 .rpc_call_done = nfs_direct_read_result,
294 .rpc_release = nfs_readdata_release,
298 * For each nfs_read_data struct that was allocated on the list, dispatch
299 * an NFS READ operation
301 static void nfs_direct_read_schedule(struct nfs_direct_req *dreq, unsigned long user_addr, size_t count, loff_t pos)
303 struct file *file = dreq->filp;
304 struct inode *inode = file->f_mapping->host;
305 struct nfs_open_context *ctx = (struct nfs_open_context *)
307 struct list_head *list = &dreq->list;
308 struct page **pages = dreq->pages;
309 size_t rsize = NFS_SERVER(inode)->rsize;
310 unsigned int curpage, pgbase;
313 pgbase = user_addr & ~PAGE_MASK;
315 struct nfs_read_data *data;
322 data = list_entry(list->next, struct nfs_read_data, pages);
323 list_del_init(&data->pages);
326 data->cred = ctx->cred;
327 data->args.fh = NFS_FH(inode);
328 data->args.context = ctx;
329 data->args.offset = pos;
330 data->args.pgbase = pgbase;
331 data->args.pages = &pages[curpage];
332 data->args.count = bytes;
333 data->res.fattr = &data->fattr;
335 data->res.count = bytes;
337 rpc_init_task(&data->task, NFS_CLIENT(inode), RPC_TASK_ASYNC,
338 &nfs_read_direct_ops, data);
339 NFS_PROTO(inode)->read_setup(data);
341 data->task.tk_cookie = (unsigned long) inode;
344 rpc_execute(&data->task);
347 dfprintk(VFS, "NFS: %4d initiated direct read call (req %s/%Ld, %u bytes @ offset %Lu)\n",
350 (long long)NFS_FILEID(inode),
352 (unsigned long long)data->args.offset);
356 curpage += pgbase >> PAGE_SHIFT;
357 pgbase &= ~PAGE_MASK;
360 } while (count != 0);
363 static ssize_t nfs_direct_read(struct kiocb *iocb, unsigned long user_addr, size_t count, loff_t pos, struct page **pages, unsigned int nr_pages)
367 struct inode *inode = iocb->ki_filp->f_mapping->host;
368 struct rpc_clnt *clnt = NFS_CLIENT(inode);
369 struct nfs_direct_req *dreq;
371 dreq = nfs_direct_read_alloc(count, NFS_SERVER(inode)->rsize);
376 dreq->npages = nr_pages;
378 dreq->filp = iocb->ki_filp;
379 if (!is_sync_kiocb(iocb))
382 nfs_add_stats(inode, NFSIOS_DIRECTREADBYTES, count);
383 rpc_clnt_sigmask(clnt, &oldset);
384 nfs_direct_read_schedule(dreq, user_addr, count, pos);
385 result = nfs_direct_wait(dreq);
386 rpc_clnt_sigunmask(clnt, &oldset);
391 static struct nfs_direct_req *nfs_direct_write_alloc(size_t nbytes, size_t wsize)
393 struct list_head *list;
394 struct nfs_direct_req *dreq;
395 unsigned int wpages = (wsize + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
397 dreq = nfs_direct_req_alloc();
403 struct nfs_write_data *data = nfs_writedata_alloc(wpages);
405 if (unlikely(!data)) {
406 while (!list_empty(list)) {
407 data = list_entry(list->next,
408 struct nfs_write_data, pages);
409 list_del(&data->pages);
410 nfs_writedata_free(data);
412 kref_put(&dreq->kref, nfs_direct_req_release);
416 INIT_LIST_HEAD(&data->pages);
417 list_add(&data->pages, list);
419 data->req = (struct nfs_page *) dreq;
425 kref_get(&dreq->kref);
430 * NB: Return the value of the first error return code. Subsequent
431 * errors after the first one are ignored.
433 static void nfs_direct_write_result(struct rpc_task *task, void *calldata)
435 struct nfs_write_data *data = calldata;
436 struct nfs_direct_req *dreq = (struct nfs_direct_req *) data->req;
437 int status = task->tk_status;
439 if (nfs_writeback_done(task, data) != 0)
441 /* If the server fell back to an UNSTABLE write, it's an error. */
442 if (unlikely(data->res.verf->committed != NFS_FILE_SYNC))
445 spin_lock(&dreq->lock);
447 if (likely(status >= 0))
448 dreq->count += data->res.count;
450 dreq->error = status;
452 if (--dreq->outstanding) {
453 spin_unlock(&dreq->lock);
457 spin_unlock(&dreq->lock);
459 nfs_end_data_update(data->inode);
460 nfs_direct_complete(dreq);
463 static const struct rpc_call_ops nfs_write_direct_ops = {
464 .rpc_call_done = nfs_direct_write_result,
465 .rpc_release = nfs_writedata_release,
469 * For each nfs_write_data struct that was allocated on the list, dispatch
470 * an NFS WRITE operation
472 * XXX: For now, support only FILE_SYNC writes. Later we may add
473 * support for UNSTABLE + COMMIT.
475 static void nfs_direct_write_schedule(struct nfs_direct_req *dreq, unsigned long user_addr, size_t count, loff_t pos)
477 struct file *file = dreq->filp;
478 struct inode *inode = file->f_mapping->host;
479 struct nfs_open_context *ctx = (struct nfs_open_context *)
481 struct list_head *list = &dreq->list;
482 struct page **pages = dreq->pages;
483 size_t wsize = NFS_SERVER(inode)->wsize;
484 unsigned int curpage, pgbase;
487 pgbase = user_addr & ~PAGE_MASK;
489 struct nfs_write_data *data;
496 data = list_entry(list->next, struct nfs_write_data, pages);
497 list_del_init(&data->pages);
500 data->cred = ctx->cred;
501 data->args.fh = NFS_FH(inode);
502 data->args.context = ctx;
503 data->args.offset = pos;
504 data->args.pgbase = pgbase;
505 data->args.pages = &pages[curpage];
506 data->args.count = bytes;
507 data->res.fattr = &data->fattr;
508 data->res.count = bytes;
509 data->res.verf = &data->verf;
511 rpc_init_task(&data->task, NFS_CLIENT(inode), RPC_TASK_ASYNC,
512 &nfs_write_direct_ops, data);
513 NFS_PROTO(inode)->write_setup(data, FLUSH_STABLE);
515 data->task.tk_priority = RPC_PRIORITY_NORMAL;
516 data->task.tk_cookie = (unsigned long) inode;
519 rpc_execute(&data->task);
522 dfprintk(VFS, "NFS: %4d initiated direct write call (req %s/%Ld, %u bytes @ offset %Lu)\n",
525 (long long)NFS_FILEID(inode),
527 (unsigned long long)data->args.offset);
531 curpage += pgbase >> PAGE_SHIFT;
532 pgbase &= ~PAGE_MASK;
535 } while (count != 0);
538 static ssize_t nfs_direct_write(struct kiocb *iocb, unsigned long user_addr, size_t count, loff_t pos, struct page **pages, int nr_pages)
542 struct inode *inode = iocb->ki_filp->f_mapping->host;
543 struct rpc_clnt *clnt = NFS_CLIENT(inode);
544 struct nfs_direct_req *dreq;
546 dreq = nfs_direct_write_alloc(count, NFS_SERVER(inode)->wsize);
551 dreq->npages = nr_pages;
553 dreq->filp = iocb->ki_filp;
554 if (!is_sync_kiocb(iocb))
557 nfs_add_stats(inode, NFSIOS_DIRECTWRITTENBYTES, count);
559 nfs_begin_data_update(inode);
561 rpc_clnt_sigmask(clnt, &oldset);
562 nfs_direct_write_schedule(dreq, user_addr, count, pos);
563 result = nfs_direct_wait(dreq);
564 rpc_clnt_sigunmask(clnt, &oldset);
570 * nfs_file_direct_read - file direct read operation for NFS files
571 * @iocb: target I/O control block
572 * @buf: user's buffer into which to read data
573 * @count: number of bytes to read
574 * @pos: byte offset in file where reading starts
576 * We use this function for direct reads instead of calling
577 * generic_file_aio_read() in order to avoid gfar's check to see if
578 * the request starts before the end of the file. For that check
579 * to work, we must generate a GETATTR before each direct read, and
580 * even then there is a window between the GETATTR and the subsequent
581 * READ where the file size could change. Our preference is simply
582 * to do all reads the application wants, and the server will take
583 * care of managing the end of file boundary.
585 * This function also eliminates unnecessarily updating the file's
586 * atime locally, as the NFS server sets the file's atime, and this
587 * client must read the updated atime from the server back into its
590 ssize_t nfs_file_direct_read(struct kiocb *iocb, char __user *buf, size_t count, loff_t pos)
592 ssize_t retval = -EINVAL;
595 struct file *file = iocb->ki_filp;
596 struct address_space *mapping = file->f_mapping;
598 dprintk("nfs: direct read(%s/%s, %lu@%Ld)\n",
599 file->f_dentry->d_parent->d_name.name,
600 file->f_dentry->d_name.name,
601 (unsigned long) count, (long long) pos);
606 if (!access_ok(VERIFY_WRITE, buf, count))
612 retval = nfs_sync_mapping(mapping);
616 page_count = nfs_get_user_pages(READ, (unsigned long) buf,
618 if (page_count < 0) {
619 nfs_free_user_pages(pages, 0, 0);
624 retval = nfs_direct_read(iocb, (unsigned long) buf, count, pos,
627 iocb->ki_pos = pos + retval;
634 * nfs_file_direct_write - file direct write operation for NFS files
635 * @iocb: target I/O control block
636 * @buf: user's buffer from which to write data
637 * @count: number of bytes to write
638 * @pos: byte offset in file where writing starts
640 * We use this function for direct writes instead of calling
641 * generic_file_aio_write() in order to avoid taking the inode
642 * semaphore and updating the i_size. The NFS server will set
643 * the new i_size and this client must read the updated size
644 * back into its cache. We let the server do generic write
645 * parameter checking and report problems.
647 * We also avoid an unnecessary invocation of generic_osync_inode(),
648 * as it is fairly meaningless to sync the metadata of an NFS file.
650 * We eliminate local atime updates, see direct read above.
652 * We avoid unnecessary page cache invalidations for normal cached
653 * readers of this file.
655 * Note that O_APPEND is not supported for NFS direct writes, as there
656 * is no atomic O_APPEND write facility in the NFS protocol.
658 ssize_t nfs_file_direct_write(struct kiocb *iocb, const char __user *buf, size_t count, loff_t pos)
663 struct file *file = iocb->ki_filp;
664 struct address_space *mapping = file->f_mapping;
666 dfprintk(VFS, "nfs: direct write(%s/%s, %lu@%Ld)\n",
667 file->f_dentry->d_parent->d_name.name,
668 file->f_dentry->d_name.name,
669 (unsigned long) count, (long long) pos);
671 retval = generic_write_checks(file, &pos, &count, 0);
676 if ((ssize_t) count < 0)
683 if (!access_ok(VERIFY_READ, buf, count))
686 retval = nfs_sync_mapping(mapping);
690 page_count = nfs_get_user_pages(WRITE, (unsigned long) buf,
692 if (page_count < 0) {
693 nfs_free_user_pages(pages, 0, 0);
698 retval = nfs_direct_write(iocb, (unsigned long) buf, count,
699 pos, pages, page_count);
702 * XXX: nfs_end_data_update() already ensures this file's
703 * cached data is subsequently invalidated. Do we really
704 * need to call invalidate_inode_pages2() again here?
706 * For aio writes, this invalidation will almost certainly
707 * occur before the writes complete. Kind of racey.
709 if (mapping->nrpages)
710 invalidate_inode_pages2(mapping);
713 iocb->ki_pos = pos + retval;
720 * nfs_init_directcache - create a slab cache for nfs_direct_req structures
723 int nfs_init_directcache(void)
725 nfs_direct_cachep = kmem_cache_create("nfs_direct_cache",
726 sizeof(struct nfs_direct_req),
727 0, SLAB_RECLAIM_ACCOUNT,
729 if (nfs_direct_cachep == NULL)
736 * nfs_init_directcache - destroy the slab cache for nfs_direct_req structures
739 void nfs_destroy_directcache(void)
741 if (kmem_cache_destroy(nfs_direct_cachep))
742 printk(KERN_INFO "nfs_direct_cache: not all structures were freed\n");