1 /* 2 * linux/fs/nfs/pagelist.c 3 * 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. 7 * 8 * Copyright 2000, 2001 (c) Trond Myklebust <trond.myklebust@fys.uio.no> 9 * 10 */ 11 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> 21 22 #define NFS_PARANOIA 1 23 24 static kmem_cache_t *nfs_page_cachep; 25 26 static inline struct nfs_page * 27 nfs_page_alloc(void) 28 { 29 struct nfs_page *p; 30 p = kmem_cache_alloc(nfs_page_cachep, SLAB_KERNEL); 31 if (p) { 32 memset(p, 0, sizeof(*p)); 33 INIT_LIST_HEAD(&p->wb_list); 34 } 35 return p; 36 } 37 38 static inline void 39 nfs_page_free(struct nfs_page *p) 40 { 41 kmem_cache_free(nfs_page_cachep, p); 42 } 43 44 /** 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 51 * 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 55 * of dirty pages. 56 * User should ensure it is safe to sleep in this function. 57 */ 58 struct nfs_page * 59 nfs_create_request(struct nfs_open_context *ctx, struct inode *inode, 60 struct page *page, 61 unsigned int offset, unsigned int count) 62 { 63 struct nfs_server *server = NFS_SERVER(inode); 64 struct nfs_page *req; 65 66 /* Deal with hard limits. */ 67 for (;;) { 68 /* try to allocate the request struct */ 69 req = nfs_page_alloc(); 70 if (req != NULL) 71 break; 72 73 /* Try to free up at least one request in order to stay 74 * below the hard limit 75 */ 76 if (signalled() && (server->flags & NFS_MOUNT_INTR)) 77 return ERR_PTR(-ERESTARTSYS); 78 yield(); 79 } 80 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. */ 84 req->wb_page = page; 85 atomic_set(&req->wb_complete, 0); 86 req->wb_index = page->index; 87 page_cache_get(page); 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); 93 94 return req; 95 } 96 97 /** 98 * nfs_unlock_request - Unlock request and wake up sleepers. 99 * @req: 100 */ 101 void nfs_unlock_request(struct nfs_page *req) 102 { 103 if (!NFS_WBACK_BUSY(req)) { 104 printk(KERN_ERR "NFS: Invalid unlock attempted\n"); 105 BUG(); 106 } 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); 112 } 113 114 /** 115 * nfs_set_page_writeback_locked - Lock a request for writeback 116 * @req: 117 */ 118 int nfs_set_page_writeback_locked(struct nfs_page *req) 119 { 120 struct nfs_inode *nfsi = NFS_I(req->wb_context->dentry->d_inode); 121 122 if (!nfs_lock_request(req)) 123 return 0; 124 radix_tree_tag_set(&nfsi->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_WRITEBACK); 125 return 1; 126 } 127 128 /** 129 * nfs_clear_page_writeback - Unlock request and wake up sleepers 130 */ 131 void nfs_clear_page_writeback(struct nfs_page *req) 132 { 133 struct nfs_inode *nfsi = NFS_I(req->wb_context->dentry->d_inode); 134 135 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); 139 } 140 141 /** 142 * nfs_clear_request - Free up all resources allocated to the request 143 * @req: 144 * 145 * Release page resources associated with a write request after it 146 * has completed. 147 */ 148 void nfs_clear_request(struct nfs_page *req) 149 { 150 if (req->wb_page) { 151 page_cache_release(req->wb_page); 152 req->wb_page = NULL; 153 } 154 } 155 156 157 /** 158 * nfs_release_request - Release the count on an NFS read/write request 159 * @req: request to release 160 * 161 * Note: Should never be called with the spinlock held! 162 */ 163 void 164 nfs_release_request(struct nfs_page *req) 165 { 166 if (!atomic_dec_and_test(&req->wb_count)) 167 return; 168 169 #ifdef NFS_PARANOIA 170 BUG_ON (!list_empty(&req->wb_list)); 171 BUG_ON (NFS_WBACK_BUSY(req)); 172 #endif 173 174 /* Release struct file or cached credential */ 175 nfs_clear_request(req); 176 put_nfs_open_context(req->wb_context); 177 nfs_page_free(req); 178 } 179 180 static int nfs_wait_bit_interruptible(void *word) 181 { 182 int ret = 0; 183 184 if (signal_pending(current)) 185 ret = -ERESTARTSYS; 186 else 187 schedule(); 188 return ret; 189 } 190 191 /** 192 * nfs_wait_on_request - Wait for a request to complete. 193 * @req: request to wait upon. 194 * 195 * Interruptible by signals only if mounted with intr flag. 196 * The user is responsible for holding a count on the request. 197 */ 198 int 199 nfs_wait_on_request(struct nfs_page *req) 200 { 201 struct rpc_clnt *clnt = NFS_CLIENT(req->wb_context->dentry->d_inode); 202 sigset_t oldmask; 203 int ret = 0; 204 205 if (!test_bit(PG_BUSY, &req->wb_flags)) 206 goto out; 207 /* 208 * Note: the call to rpc_clnt_sigmask() suffices to ensure that we 209 * are not interrupted if intr flag is not set 210 */ 211 rpc_clnt_sigmask(clnt, &oldmask); 212 ret = out_of_line_wait_on_bit(&req->wb_flags, PG_BUSY, 213 nfs_wait_bit_interruptible, TASK_INTERRUPTIBLE); 214 rpc_clnt_sigunmask(clnt, &oldmask); 215 out: 216 return ret; 217 } 218 219 /** 220 * nfs_coalesce_requests - Split coalesced requests out from a list. 221 * @head: source list 222 * @dst: destination list 223 * @nmax: maximum number of requests to coalesce 224 * 225 * Moves a maximum of 'nmax' elements from one list to another. 226 * The elements are checked to ensure that they form a contiguous set 227 * of pages, and that the RPC credentials are the same. 228 */ 229 int 230 nfs_coalesce_requests(struct list_head *head, struct list_head *dst, 231 unsigned int nmax) 232 { 233 struct nfs_page *req = NULL; 234 unsigned int npages = 0; 235 236 while (!list_empty(head)) { 237 struct nfs_page *prev = req; 238 239 req = nfs_list_entry(head->next); 240 if (prev) { 241 if (req->wb_context->cred != prev->wb_context->cred) 242 break; 243 if (req->wb_context->lockowner != prev->wb_context->lockowner) 244 break; 245 if (req->wb_context->state != prev->wb_context->state) 246 break; 247 if (req->wb_index != (prev->wb_index + 1)) 248 break; 249 250 if (req->wb_pgbase != 0) 251 break; 252 } 253 nfs_list_remove_request(req); 254 nfs_list_add_request(req, dst); 255 npages++; 256 if (req->wb_pgbase + req->wb_bytes != PAGE_CACHE_SIZE) 257 break; 258 if (npages >= nmax) 259 break; 260 } 261 return npages; 262 } 263 264 #define NFS_SCAN_MAXENTRIES 16 265 /** 266 * nfs_scan_lock_dirty - Scan the radix tree for dirty requests 267 * @nfsi: NFS inode 268 * @dst: Destination list 269 * @idx_start: lower bound of page->index to scan 270 * @npages: idx_start + npages sets the upper bound to scan. 271 * 272 * Moves elements from one of the inode request lists. 273 * If the number of requests is set to 0, the entire address_space 274 * starting at index idx_start, is scanned. 275 * The requests are *not* checked to ensure that they form a contiguous set. 276 * You must be holding the inode's req_lock when calling this function 277 */ 278 int 279 nfs_scan_lock_dirty(struct nfs_inode *nfsi, struct list_head *dst, 280 unsigned long idx_start, unsigned int npages) 281 { 282 struct nfs_page *pgvec[NFS_SCAN_MAXENTRIES]; 283 struct nfs_page *req; 284 unsigned long idx_end; 285 int found, i; 286 int res; 287 288 res = 0; 289 if (npages == 0) 290 idx_end = ~0; 291 else 292 idx_end = idx_start + npages - 1; 293 294 for (;;) { 295 found = radix_tree_gang_lookup_tag(&nfsi->nfs_page_tree, 296 (void **)&pgvec[0], idx_start, NFS_SCAN_MAXENTRIES, 297 NFS_PAGE_TAG_DIRTY); 298 if (found <= 0) 299 break; 300 for (i = 0; i < found; i++) { 301 req = pgvec[i]; 302 if (req->wb_index > idx_end) 303 goto out; 304 305 idx_start = req->wb_index + 1; 306 307 if (nfs_set_page_writeback_locked(req)) { 308 radix_tree_tag_clear(&nfsi->nfs_page_tree, 309 req->wb_index, NFS_PAGE_TAG_DIRTY); 310 nfs_list_remove_request(req); 311 nfs_list_add_request(req, dst); 312 res++; 313 } 314 } 315 } 316 out: 317 return res; 318 } 319 320 /** 321 * nfs_scan_list - Scan a list for matching requests 322 * @head: One of the NFS inode request lists 323 * @dst: Destination list 324 * @idx_start: lower bound of page->index to scan 325 * @npages: idx_start + npages sets the upper bound to scan. 326 * 327 * Moves elements from one of the inode request lists. 328 * If the number of requests is set to 0, the entire address_space 329 * starting at index idx_start, is scanned. 330 * The requests are *not* checked to ensure that they form a contiguous set. 331 * You must be holding the inode's req_lock when calling this function 332 */ 333 int 334 nfs_scan_list(struct list_head *head, struct list_head *dst, 335 unsigned long idx_start, unsigned int npages) 336 { 337 struct list_head *pos, *tmp; 338 struct nfs_page *req; 339 unsigned long idx_end; 340 int res; 341 342 res = 0; 343 if (npages == 0) 344 idx_end = ~0; 345 else 346 idx_end = idx_start + npages - 1; 347 348 list_for_each_safe(pos, tmp, head) { 349 350 req = nfs_list_entry(pos); 351 352 if (req->wb_index < idx_start) 353 continue; 354 if (req->wb_index > idx_end) 355 break; 356 357 if (!nfs_set_page_writeback_locked(req)) 358 continue; 359 nfs_list_remove_request(req); 360 nfs_list_add_request(req, dst); 361 res++; 362 } 363 return res; 364 } 365 366 int nfs_init_nfspagecache(void) 367 { 368 nfs_page_cachep = kmem_cache_create("nfs_page", 369 sizeof(struct nfs_page), 370 0, SLAB_HWCACHE_ALIGN, 371 NULL, NULL); 372 if (nfs_page_cachep == NULL) 373 return -ENOMEM; 374 375 return 0; 376 } 377 378 void nfs_destroy_nfspagecache(void) 379 { 380 if (kmem_cache_destroy(nfs_page_cachep)) 381 printk(KERN_INFO "nfs_page: not all structures were freed\n"); 382 } 383 384