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/config.h>
13 #include <linux/slab.h>
14 #include <linux/file.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>
22 #define NFS_PARANOIA 1
24 static kmem_cache_t *nfs_page_cachep;
26 static inline struct nfs_page *
30 p = kmem_cache_alloc(nfs_page_cachep, SLAB_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, and avoids
54 * a possible deadlock when we reach the hard limit on the number
56 * User should ensure it is safe to sleep in this function.
59 nfs_create_request(struct nfs_open_context *ctx, struct inode *inode,
61 unsigned int offset, unsigned int count)
63 struct nfs_server *server = NFS_SERVER(inode);
66 /* Deal with hard limits. */
68 /* try to allocate the request struct */
69 req = nfs_page_alloc();
73 /* Try to free up at least one request in order to stay
74 * below the hard limit
76 if (signalled() && (server->flags & NFS_MOUNT_INTR))
77 return ERR_PTR(-ERESTARTSYS);
81 /* Initialize the request struct. Initially, we assume a
82 * long write-back delay. This will be adjusted in
83 * update_nfs_request below if the region is not locked. */
85 atomic_set(&req->wb_complete, 0);
86 req->wb_index = page->index;
88 req->wb_offset = offset;
89 req->wb_pgbase = offset;
90 req->wb_bytes = count;
91 atomic_set(&req->wb_count, 1);
92 req->wb_context = get_nfs_open_context(ctx);
98 * nfs_unlock_request - Unlock request and wake up sleepers.
101 void nfs_unlock_request(struct nfs_page *req)
103 if (!NFS_WBACK_BUSY(req)) {
104 printk(KERN_ERR "NFS: Invalid unlock attempted\n");
107 smp_mb__before_clear_bit();
108 clear_bit(PG_BUSY, &req->wb_flags);
109 smp_mb__after_clear_bit();
110 wake_up_bit(&req->wb_flags, PG_BUSY);
111 nfs_release_request(req);
115 * nfs_set_page_writeback_locked - Lock a request for writeback
118 int nfs_set_page_writeback_locked(struct nfs_page *req)
120 struct nfs_inode *nfsi = NFS_I(req->wb_context->dentry->d_inode);
122 if (!nfs_lock_request(req))
124 radix_tree_tag_set(&nfsi->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_WRITEBACK);
129 * nfs_clear_page_writeback - Unlock request and wake up sleepers
131 void nfs_clear_page_writeback(struct nfs_page *req)
133 struct nfs_inode *nfsi = NFS_I(req->wb_context->dentry->d_inode);
135 spin_lock(&nfsi->req_lock);
136 radix_tree_tag_clear(&nfsi->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_WRITEBACK);
137 spin_unlock(&nfsi->req_lock);
138 nfs_unlock_request(req);
142 * nfs_clear_request - Free up all resources allocated to the request
145 * Release page resources associated with a write request after it
148 void nfs_clear_request(struct nfs_page *req)
151 page_cache_release(req->wb_page);
158 * nfs_release_request - Release the count on an NFS read/write request
159 * @req: request to release
161 * Note: Should never be called with the spinlock held!
164 nfs_release_request(struct nfs_page *req)
166 if (!atomic_dec_and_test(&req->wb_count))
170 BUG_ON (!list_empty(&req->wb_list));
171 BUG_ON (NFS_WBACK_BUSY(req));
174 /* Release struct file or cached credential */
175 nfs_clear_request(req);
176 put_nfs_open_context(req->wb_context);
181 * nfs_list_add_request - Insert a request into a sorted list
183 * @head: head of list into which to insert the request.
185 * Note that the wb_list is sorted by page index in order to facilitate
186 * coalescing of requests.
187 * We use an insertion sort that is optimized for the case of appended
191 nfs_list_add_request(struct nfs_page *req, struct list_head *head)
193 struct list_head *pos;
196 if (!list_empty(&req->wb_list)) {
197 printk(KERN_ERR "NFS: Add to list failed!\n");
201 list_for_each_prev(pos, head) {
202 struct nfs_page *p = nfs_list_entry(pos);
203 if (p->wb_index < req->wb_index)
206 list_add(&req->wb_list, pos);
207 req->wb_list_head = head;
210 static int nfs_wait_bit_interruptible(void *word)
214 if (signal_pending(current))
222 * nfs_wait_on_request - Wait for a request to complete.
223 * @req: request to wait upon.
225 * Interruptible by signals only if mounted with intr flag.
226 * The user is responsible for holding a count on the request.
229 nfs_wait_on_request(struct nfs_page *req)
231 struct rpc_clnt *clnt = NFS_CLIENT(req->wb_context->dentry->d_inode);
235 if (!test_bit(PG_BUSY, &req->wb_flags))
238 * Note: the call to rpc_clnt_sigmask() suffices to ensure that we
239 * are not interrupted if intr flag is not set
241 rpc_clnt_sigmask(clnt, &oldmask);
242 ret = out_of_line_wait_on_bit(&req->wb_flags, PG_BUSY,
243 nfs_wait_bit_interruptible, TASK_INTERRUPTIBLE);
244 rpc_clnt_sigunmask(clnt, &oldmask);
250 * nfs_coalesce_requests - Split coalesced requests out from a list.
252 * @dst: destination list
253 * @nmax: maximum number of requests to coalesce
255 * Moves a maximum of 'nmax' elements from one list to another.
256 * The elements are checked to ensure that they form a contiguous set
257 * of pages, and that the RPC credentials are the same.
260 nfs_coalesce_requests(struct list_head *head, struct list_head *dst,
263 struct nfs_page *req = NULL;
264 unsigned int npages = 0;
266 while (!list_empty(head)) {
267 struct nfs_page *prev = req;
269 req = nfs_list_entry(head->next);
271 if (req->wb_context->cred != prev->wb_context->cred)
273 if (req->wb_context->lockowner != prev->wb_context->lockowner)
275 if (req->wb_context->state != prev->wb_context->state)
277 if (req->wb_index != (prev->wb_index + 1))
280 if (req->wb_pgbase != 0)
283 nfs_list_remove_request(req);
284 nfs_list_add_request(req, dst);
286 if (req->wb_pgbase + req->wb_bytes != PAGE_CACHE_SIZE)
295 * nfs_scan_list - Scan a list for matching requests
296 * @head: One of the NFS inode request lists
297 * @dst: Destination list
298 * @idx_start: lower bound of page->index to scan
299 * @npages: idx_start + npages sets the upper bound to scan.
301 * Moves elements from one of the inode request lists.
302 * If the number of requests is set to 0, the entire address_space
303 * starting at index idx_start, is scanned.
304 * The requests are *not* checked to ensure that they form a contiguous set.
305 * You must be holding the inode's req_lock when calling this function
308 nfs_scan_list(struct list_head *head, struct list_head *dst,
309 unsigned long idx_start, unsigned int npages)
311 struct list_head *pos, *tmp;
312 struct nfs_page *req;
313 unsigned long idx_end;
320 idx_end = idx_start + npages - 1;
322 list_for_each_safe(pos, tmp, head) {
324 req = nfs_list_entry(pos);
326 if (req->wb_index < idx_start)
328 if (req->wb_index > idx_end)
331 if (!nfs_set_page_writeback_locked(req))
333 nfs_list_remove_request(req);
334 nfs_list_add_request(req, dst);
340 int nfs_init_nfspagecache(void)
342 nfs_page_cachep = kmem_cache_create("nfs_page",
343 sizeof(struct nfs_page),
344 0, SLAB_HWCACHE_ALIGN,
346 if (nfs_page_cachep == NULL)
352 void nfs_destroy_nfspagecache(void)
354 if (kmem_cache_destroy(nfs_page_cachep))
355 printk(KERN_INFO "nfs_page: not all structures were freed\n");