2 * linux/fs/nfs/pagelist.c
4 * A set of helper functions for managing NFS read and write requests.
5 * The main purpose of these routines is to provide support for the
6 * coalescing of several requests into a single RPC call.
8 * Copyright 2000, 2001 (c) Trond Myklebust <trond.myklebust@fys.uio.no>
12 #include <linux/slab.h>
13 #include <linux/file.h>
14 #include <linux/sched.h>
15 #include <linux/sunrpc/clnt.h>
16 #include <linux/nfs3.h>
17 #include <linux/nfs4.h>
18 #include <linux/nfs_page.h>
19 #include <linux/nfs_fs.h>
20 #include <linux/nfs_mount.h>
24 static struct kmem_cache *nfs_page_cachep;
26 static inline struct nfs_page *
30 p = kmem_cache_alloc(nfs_page_cachep, GFP_KERNEL);
32 memset(p, 0, sizeof(*p));
33 INIT_LIST_HEAD(&p->wb_list);
39 nfs_page_free(struct nfs_page *p)
41 kmem_cache_free(nfs_page_cachep, p);
45 * nfs_create_request - Create an NFS read/write request.
46 * @file: file descriptor to use
47 * @inode: inode to which the request is attached
48 * @page: page to write
49 * @offset: starting offset within the page for the write
50 * @count: number of bytes to read/write
52 * The page must be locked by the caller. This makes sure we never
53 * create two different requests for the same page.
54 * User should ensure it is safe to sleep in this function.
57 nfs_create_request(struct nfs_open_context *ctx, struct inode *inode,
59 unsigned int offset, unsigned int count)
63 /* try to allocate the request struct */
64 req = nfs_page_alloc();
66 return ERR_PTR(-ENOMEM);
68 /* get lock context early so we can deal with alloc failures */
69 req->wb_lock_context = nfs_get_lock_context(ctx);
70 if (req->wb_lock_context == NULL) {
72 return ERR_PTR(-ENOMEM);
75 /* Initialize the request struct. Initially, we assume a
76 * long write-back delay. This will be adjusted in
77 * update_nfs_request below if the region is not locked. */
79 atomic_set(&req->wb_complete, 0);
80 req->wb_index = page->index;
82 BUG_ON(PagePrivate(page));
83 BUG_ON(!PageLocked(page));
84 BUG_ON(page->mapping->host != inode);
85 req->wb_offset = offset;
86 req->wb_pgbase = offset;
87 req->wb_bytes = count;
88 req->wb_context = get_nfs_open_context(ctx);
89 kref_init(&req->wb_kref);
94 * nfs_unlock_request - Unlock request and wake up sleepers.
97 void nfs_unlock_request(struct nfs_page *req)
99 if (!NFS_WBACK_BUSY(req)) {
100 printk(KERN_ERR "NFS: Invalid unlock attempted\n");
103 smp_mb__before_clear_bit();
104 clear_bit(PG_BUSY, &req->wb_flags);
105 smp_mb__after_clear_bit();
106 wake_up_bit(&req->wb_flags, PG_BUSY);
107 nfs_release_request(req);
111 * nfs_set_page_tag_locked - Tag a request as locked
114 int nfs_set_page_tag_locked(struct nfs_page *req)
116 if (!nfs_lock_request_dontget(req))
118 if (req->wb_page != NULL)
119 radix_tree_tag_set(&NFS_I(req->wb_context->path.dentry->d_inode)->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_LOCKED);
124 * nfs_clear_page_tag_locked - Clear request tag and wake up sleepers
126 void nfs_clear_page_tag_locked(struct nfs_page *req)
128 if (req->wb_page != NULL) {
129 struct inode *inode = req->wb_context->path.dentry->d_inode;
130 struct nfs_inode *nfsi = NFS_I(inode);
132 spin_lock(&inode->i_lock);
133 radix_tree_tag_clear(&nfsi->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_LOCKED);
134 nfs_unlock_request(req);
135 spin_unlock(&inode->i_lock);
137 nfs_unlock_request(req);
141 * nfs_clear_request - Free up all resources allocated to the request
144 * Release page and open context resources associated with a read/write
145 * request after it has completed.
147 void nfs_clear_request(struct nfs_page *req)
149 struct page *page = req->wb_page;
150 struct nfs_open_context *ctx = req->wb_context;
151 struct nfs_lock_context *l_ctx = req->wb_lock_context;
154 page_cache_release(page);
158 nfs_put_lock_context(l_ctx);
159 req->wb_lock_context = NULL;
162 put_nfs_open_context(ctx);
163 req->wb_context = NULL;
169 * nfs_release_request - Release the count on an NFS read/write request
170 * @req: request to release
172 * Note: Should never be called with the spinlock held!
174 static void nfs_free_request(struct kref *kref)
176 struct nfs_page *req = container_of(kref, struct nfs_page, wb_kref);
178 /* Release struct file and open context */
179 nfs_clear_request(req);
183 void nfs_release_request(struct nfs_page *req)
185 kref_put(&req->wb_kref, nfs_free_request);
188 static int nfs_wait_bit_uninterruptible(void *word)
195 * nfs_wait_on_request - Wait for a request to complete.
196 * @req: request to wait upon.
198 * Interruptible by fatal signals only.
199 * The user is responsible for holding a count on the request.
202 nfs_wait_on_request(struct nfs_page *req)
204 return wait_on_bit(&req->wb_flags, PG_BUSY,
205 nfs_wait_bit_uninterruptible,
206 TASK_UNINTERRUPTIBLE);
210 * nfs_pageio_init - initialise a page io descriptor
211 * @desc: pointer to descriptor
212 * @inode: pointer to inode
213 * @doio: pointer to io function
214 * @bsize: io block size
215 * @io_flags: extra parameters for the io function
217 void nfs_pageio_init(struct nfs_pageio_descriptor *desc,
219 int (*doio)(struct inode *, struct list_head *, unsigned int, size_t, int),
223 INIT_LIST_HEAD(&desc->pg_list);
224 desc->pg_bytes_written = 0;
226 desc->pg_bsize = bsize;
228 desc->pg_inode = inode;
229 desc->pg_doio = doio;
230 desc->pg_ioflags = io_flags;
235 * nfs_can_coalesce_requests - test two requests for compatibility
236 * @prev: pointer to nfs_page
237 * @req: pointer to nfs_page
239 * The nfs_page structures 'prev' and 'req' are compared to ensure that the
240 * page data area they describe is contiguous, and that their RPC
241 * credentials, NFSv4 open state, and lockowners are the same.
243 * Return 'true' if this is the case, else return 'false'.
245 static int nfs_can_coalesce_requests(struct nfs_page *prev,
246 struct nfs_page *req)
248 if (req->wb_context->cred != prev->wb_context->cred)
250 if (req->wb_lock_context->lockowner != prev->wb_lock_context->lockowner)
252 if (req->wb_context->state != prev->wb_context->state)
254 if (req->wb_index != (prev->wb_index + 1))
256 if (req->wb_pgbase != 0)
258 if (prev->wb_pgbase + prev->wb_bytes != PAGE_CACHE_SIZE)
264 * nfs_pageio_do_add_request - Attempt to coalesce a request into a page list.
265 * @desc: destination io descriptor
268 * Returns true if the request 'req' was successfully coalesced into the
269 * existing list of pages 'desc'.
271 static int nfs_pageio_do_add_request(struct nfs_pageio_descriptor *desc,
272 struct nfs_page *req)
274 size_t newlen = req->wb_bytes;
276 if (desc->pg_count != 0) {
277 struct nfs_page *prev;
280 * FIXME: ideally we should be able to coalesce all requests
281 * that are not block boundary aligned, but currently this
282 * is problematic for the case of bsize < PAGE_CACHE_SIZE,
283 * since nfs_flush_multi and nfs_pagein_multi assume you
284 * can have only one struct nfs_page.
286 if (desc->pg_bsize < PAGE_SIZE)
288 newlen += desc->pg_count;
289 if (newlen > desc->pg_bsize)
291 prev = nfs_list_entry(desc->pg_list.prev);
292 if (!nfs_can_coalesce_requests(prev, req))
295 desc->pg_base = req->wb_pgbase;
296 nfs_list_remove_request(req);
297 nfs_list_add_request(req, &desc->pg_list);
298 desc->pg_count = newlen;
303 * Helper for nfs_pageio_add_request and nfs_pageio_complete
305 static void nfs_pageio_doio(struct nfs_pageio_descriptor *desc)
307 if (!list_empty(&desc->pg_list)) {
308 int error = desc->pg_doio(desc->pg_inode,
310 nfs_page_array_len(desc->pg_base,
315 desc->pg_error = error;
317 desc->pg_bytes_written += desc->pg_count;
319 if (list_empty(&desc->pg_list)) {
326 * nfs_pageio_add_request - Attempt to coalesce a request into a page list.
327 * @desc: destination io descriptor
330 * Returns true if the request 'req' was successfully coalesced into the
331 * existing list of pages 'desc'.
333 int nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
334 struct nfs_page *req)
336 while (!nfs_pageio_do_add_request(desc, req)) {
337 nfs_pageio_doio(desc);
338 if (desc->pg_error < 0)
345 * nfs_pageio_complete - Complete I/O on an nfs_pageio_descriptor
346 * @desc: pointer to io descriptor
348 void nfs_pageio_complete(struct nfs_pageio_descriptor *desc)
350 nfs_pageio_doio(desc);
354 * nfs_pageio_cond_complete - Conditional I/O completion
355 * @desc: pointer to io descriptor
358 * It is important to ensure that processes don't try to take locks
359 * on non-contiguous ranges of pages as that might deadlock. This
360 * function should be called before attempting to wait on a locked
361 * nfs_page. It will complete the I/O if the page index 'index'
362 * is not contiguous with the existing list of pages in 'desc'.
364 void nfs_pageio_cond_complete(struct nfs_pageio_descriptor *desc, pgoff_t index)
366 if (!list_empty(&desc->pg_list)) {
367 struct nfs_page *prev = nfs_list_entry(desc->pg_list.prev);
368 if (index != prev->wb_index + 1)
369 nfs_pageio_doio(desc);
373 #define NFS_SCAN_MAXENTRIES 16
375 * nfs_scan_list - Scan a list for matching requests
377 * @dst: Destination list
378 * @idx_start: lower bound of page->index to scan
379 * @npages: idx_start + npages sets the upper bound to scan.
380 * @tag: tag to scan for
382 * Moves elements from one of the inode request lists.
383 * If the number of requests is set to 0, the entire address_space
384 * starting at index idx_start, is scanned.
385 * The requests are *not* checked to ensure that they form a contiguous set.
386 * You must be holding the inode's i_lock when calling this function
388 int nfs_scan_list(struct nfs_inode *nfsi,
389 struct list_head *dst, pgoff_t idx_start,
390 unsigned int npages, int tag)
392 struct nfs_page *pgvec[NFS_SCAN_MAXENTRIES];
393 struct nfs_page *req;
402 idx_end = idx_start + npages - 1;
405 found = radix_tree_gang_lookup_tag(&nfsi->nfs_page_tree,
406 (void **)&pgvec[0], idx_start,
407 NFS_SCAN_MAXENTRIES, tag);
410 for (i = 0; i < found; i++) {
412 if (req->wb_index > idx_end)
414 idx_start = req->wb_index + 1;
415 if (nfs_set_page_tag_locked(req)) {
416 kref_get(&req->wb_kref);
417 nfs_list_remove_request(req);
418 radix_tree_tag_clear(&nfsi->nfs_page_tree,
420 nfs_list_add_request(req, dst);
426 /* for latency reduction */
427 cond_resched_lock(&nfsi->vfs_inode.i_lock);
433 int __init nfs_init_nfspagecache(void)
435 nfs_page_cachep = kmem_cache_create("nfs_page",
436 sizeof(struct nfs_page),
437 0, SLAB_HWCACHE_ALIGN,
439 if (nfs_page_cachep == NULL)
445 void nfs_destroy_nfspagecache(void)
447 kmem_cache_destroy(nfs_page_cachep);