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/slab.h> 13 #include <linux/file.h> 14 #include <linux/sunrpc/clnt.h> 15 #include <linux/nfs3.h> 16 #include <linux/nfs4.h> 17 #include <linux/nfs_page.h> 18 #include <linux/nfs_fs.h> 19 #include <linux/nfs_mount.h> 20 21 #define NFS_PARANOIA 1 22 23 static kmem_cache_t *nfs_page_cachep; 24 25 static inline struct nfs_page * 26 nfs_page_alloc(void) 27 { 28 struct nfs_page *p; 29 p = kmem_cache_alloc(nfs_page_cachep, SLAB_KERNEL); 30 if (p) { 31 memset(p, 0, sizeof(*p)); 32 INIT_LIST_HEAD(&p->wb_list); 33 } 34 return p; 35 } 36 37 static inline void 38 nfs_page_free(struct nfs_page *p) 39 { 40 kmem_cache_free(nfs_page_cachep, p); 41 } 42 43 /** 44 * nfs_create_request - Create an NFS read/write request. 45 * @file: file descriptor to use 46 * @inode: inode to which the request is attached 47 * @page: page to write 48 * @offset: starting offset within the page for the write 49 * @count: number of bytes to read/write 50 * 51 * The page must be locked by the caller. This makes sure we never 52 * create two different requests for the same page, and avoids 53 * a possible deadlock when we reach the hard limit on the number 54 * of dirty pages. 55 * User should ensure it is safe to sleep in this function. 56 */ 57 struct nfs_page * 58 nfs_create_request(struct nfs_open_context *ctx, struct inode *inode, 59 struct page *page, 60 unsigned int offset, unsigned int count) 61 { 62 struct nfs_server *server = NFS_SERVER(inode); 63 struct nfs_page *req; 64 65 /* Deal with hard limits. */ 66 for (;;) { 67 /* try to allocate the request struct */ 68 req = nfs_page_alloc(); 69 if (req != NULL) 70 break; 71 72 /* Try to free up at least one request in order to stay 73 * below the hard limit 74 */ 75 if (signalled() && (server->flags & NFS_MOUNT_INTR)) 76 return ERR_PTR(-ERESTARTSYS); 77 yield(); 78 } 79 80 /* Initialize the request struct. Initially, we assume a 81 * long write-back delay. This will be adjusted in 82 * update_nfs_request below if the region is not locked. */ 83 req->wb_page = page; 84 atomic_set(&req->wb_complete, 0); 85 req->wb_index = page->index; 86 page_cache_get(page); 87 BUG_ON(PagePrivate(page)); 88 BUG_ON(!PageLocked(page)); 89 BUG_ON(page->mapping->host != inode); 90 req->wb_offset = offset; 91 req->wb_pgbase = offset; 92 req->wb_bytes = count; 93 atomic_set(&req->wb_count, 1); 94 req->wb_context = get_nfs_open_context(ctx); 95 96 return req; 97 } 98 99 /** 100 * nfs_unlock_request - Unlock request and wake up sleepers. 101 * @req: 102 */ 103 void nfs_unlock_request(struct nfs_page *req) 104 { 105 if (!NFS_WBACK_BUSY(req)) { 106 printk(KERN_ERR "NFS: Invalid unlock attempted\n"); 107 BUG(); 108 } 109 smp_mb__before_clear_bit(); 110 clear_bit(PG_BUSY, &req->wb_flags); 111 smp_mb__after_clear_bit(); 112 wake_up_bit(&req->wb_flags, PG_BUSY); 113 nfs_release_request(req); 114 } 115 116 /** 117 * nfs_set_page_writeback_locked - Lock a request for writeback 118 * @req: 119 */ 120 int nfs_set_page_writeback_locked(struct nfs_page *req) 121 { 122 struct nfs_inode *nfsi = NFS_I(req->wb_context->dentry->d_inode); 123 124 if (!nfs_lock_request(req)) 125 return 0; 126 radix_tree_tag_set(&nfsi->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_WRITEBACK); 127 return 1; 128 } 129 130 /** 131 * nfs_clear_page_writeback - Unlock request and wake up sleepers 132 */ 133 void nfs_clear_page_writeback(struct nfs_page *req) 134 { 135 struct nfs_inode *nfsi = NFS_I(req->wb_context->dentry->d_inode); 136 137 if (req->wb_page != NULL) { 138 spin_lock(&nfsi->req_lock); 139 radix_tree_tag_clear(&nfsi->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_WRITEBACK); 140 spin_unlock(&nfsi->req_lock); 141 } 142 nfs_unlock_request(req); 143 } 144 145 /** 146 * nfs_clear_request - Free up all resources allocated to the request 147 * @req: 148 * 149 * Release page resources associated with a write request after it 150 * has completed. 151 */ 152 void nfs_clear_request(struct nfs_page *req) 153 { 154 struct page *page = req->wb_page; 155 if (page != NULL) { 156 page_cache_release(page); 157 req->wb_page = NULL; 158 } 159 } 160 161 162 /** 163 * nfs_release_request - Release the count on an NFS read/write request 164 * @req: request to release 165 * 166 * Note: Should never be called with the spinlock held! 167 */ 168 void 169 nfs_release_request(struct nfs_page *req) 170 { 171 if (!atomic_dec_and_test(&req->wb_count)) 172 return; 173 174 #ifdef NFS_PARANOIA 175 BUG_ON (!list_empty(&req->wb_list)); 176 BUG_ON (NFS_WBACK_BUSY(req)); 177 #endif 178 179 /* Release struct file or cached credential */ 180 nfs_clear_request(req); 181 put_nfs_open_context(req->wb_context); 182 nfs_page_free(req); 183 } 184 185 static int nfs_wait_bit_interruptible(void *word) 186 { 187 int ret = 0; 188 189 if (signal_pending(current)) 190 ret = -ERESTARTSYS; 191 else 192 schedule(); 193 return ret; 194 } 195 196 /** 197 * nfs_wait_on_request - Wait for a request to complete. 198 * @req: request to wait upon. 199 * 200 * Interruptible by signals only if mounted with intr flag. 201 * The user is responsible for holding a count on the request. 202 */ 203 int 204 nfs_wait_on_request(struct nfs_page *req) 205 { 206 struct rpc_clnt *clnt = NFS_CLIENT(req->wb_context->dentry->d_inode); 207 sigset_t oldmask; 208 int ret = 0; 209 210 if (!test_bit(PG_BUSY, &req->wb_flags)) 211 goto out; 212 /* 213 * Note: the call to rpc_clnt_sigmask() suffices to ensure that we 214 * are not interrupted if intr flag is not set 215 */ 216 rpc_clnt_sigmask(clnt, &oldmask); 217 ret = out_of_line_wait_on_bit(&req->wb_flags, PG_BUSY, 218 nfs_wait_bit_interruptible, TASK_INTERRUPTIBLE); 219 rpc_clnt_sigunmask(clnt, &oldmask); 220 out: 221 return ret; 222 } 223 224 /** 225 * nfs_coalesce_requests - Split coalesced requests out from a list. 226 * @head: source list 227 * @dst: destination list 228 * @nmax: maximum number of requests to coalesce 229 * 230 * Moves a maximum of 'nmax' elements from one list to another. 231 * The elements are checked to ensure that they form a contiguous set 232 * of pages, and that the RPC credentials are the same. 233 */ 234 int 235 nfs_coalesce_requests(struct list_head *head, struct list_head *dst, 236 unsigned int nmax) 237 { 238 struct nfs_page *req = NULL; 239 unsigned int npages = 0; 240 241 while (!list_empty(head)) { 242 struct nfs_page *prev = req; 243 244 req = nfs_list_entry(head->next); 245 if (prev) { 246 if (req->wb_context->cred != prev->wb_context->cred) 247 break; 248 if (req->wb_context->lockowner != prev->wb_context->lockowner) 249 break; 250 if (req->wb_context->state != prev->wb_context->state) 251 break; 252 if (req->wb_index != (prev->wb_index + 1)) 253 break; 254 255 if (req->wb_pgbase != 0) 256 break; 257 } 258 nfs_list_remove_request(req); 259 nfs_list_add_request(req, dst); 260 npages++; 261 if (req->wb_pgbase + req->wb_bytes != PAGE_CACHE_SIZE) 262 break; 263 if (npages >= nmax) 264 break; 265 } 266 return npages; 267 } 268 269 #define NFS_SCAN_MAXENTRIES 16 270 /** 271 * nfs_scan_lock_dirty - Scan the radix tree for dirty requests 272 * @nfsi: NFS inode 273 * @dst: Destination list 274 * @idx_start: lower bound of page->index to scan 275 * @npages: idx_start + npages sets the upper bound to scan. 276 * 277 * Moves elements from one of the inode request lists. 278 * If the number of requests is set to 0, the entire address_space 279 * starting at index idx_start, is scanned. 280 * The requests are *not* checked to ensure that they form a contiguous set. 281 * You must be holding the inode's req_lock when calling this function 282 */ 283 int 284 nfs_scan_lock_dirty(struct nfs_inode *nfsi, struct list_head *dst, 285 unsigned long idx_start, unsigned int npages) 286 { 287 struct nfs_page *pgvec[NFS_SCAN_MAXENTRIES]; 288 struct nfs_page *req; 289 unsigned long idx_end; 290 int found, i; 291 int res; 292 293 res = 0; 294 if (npages == 0) 295 idx_end = ~0; 296 else 297 idx_end = idx_start + npages - 1; 298 299 for (;;) { 300 found = radix_tree_gang_lookup_tag(&nfsi->nfs_page_tree, 301 (void **)&pgvec[0], idx_start, NFS_SCAN_MAXENTRIES, 302 NFS_PAGE_TAG_DIRTY); 303 if (found <= 0) 304 break; 305 for (i = 0; i < found; i++) { 306 req = pgvec[i]; 307 if (req->wb_index > idx_end) 308 goto out; 309 310 idx_start = req->wb_index + 1; 311 312 if (nfs_set_page_writeback_locked(req)) { 313 radix_tree_tag_clear(&nfsi->nfs_page_tree, 314 req->wb_index, NFS_PAGE_TAG_DIRTY); 315 nfs_list_remove_request(req); 316 nfs_list_add_request(req, dst); 317 dec_zone_page_state(req->wb_page, NR_FILE_DIRTY); 318 res++; 319 } 320 } 321 } 322 out: 323 return res; 324 } 325 326 /** 327 * nfs_scan_list - Scan a list for matching requests 328 * @nfsi: NFS inode 329 * @head: One of the NFS inode request lists 330 * @dst: Destination list 331 * @idx_start: lower bound of page->index to scan 332 * @npages: idx_start + npages sets the upper bound to scan. 333 * 334 * Moves elements from one of the inode request lists. 335 * If the number of requests is set to 0, the entire address_space 336 * starting at index idx_start, is scanned. 337 * The requests are *not* checked to ensure that they form a contiguous set. 338 * You must be holding the inode's req_lock when calling this function 339 */ 340 int nfs_scan_list(struct nfs_inode *nfsi, struct list_head *head, 341 struct list_head *dst, unsigned long idx_start, 342 unsigned int npages) 343 { 344 struct nfs_page *pgvec[NFS_SCAN_MAXENTRIES]; 345 struct nfs_page *req; 346 unsigned long idx_end; 347 int found, i; 348 int res; 349 350 res = 0; 351 if (npages == 0) 352 idx_end = ~0; 353 else 354 idx_end = idx_start + npages - 1; 355 356 for (;;) { 357 found = radix_tree_gang_lookup(&nfsi->nfs_page_tree, 358 (void **)&pgvec[0], idx_start, 359 NFS_SCAN_MAXENTRIES); 360 if (found <= 0) 361 break; 362 for (i = 0; i < found; i++) { 363 req = pgvec[i]; 364 if (req->wb_index > idx_end) 365 goto out; 366 idx_start = req->wb_index + 1; 367 if (req->wb_list_head != head) 368 continue; 369 if (nfs_set_page_writeback_locked(req)) { 370 nfs_list_remove_request(req); 371 nfs_list_add_request(req, dst); 372 res++; 373 } 374 } 375 376 } 377 out: 378 return res; 379 } 380 381 int __init nfs_init_nfspagecache(void) 382 { 383 nfs_page_cachep = kmem_cache_create("nfs_page", 384 sizeof(struct nfs_page), 385 0, SLAB_HWCACHE_ALIGN, 386 NULL, NULL); 387 if (nfs_page_cachep == NULL) 388 return -ENOMEM; 389 390 return 0; 391 } 392 393 void nfs_destroy_nfspagecache(void) 394 { 395 if (kmem_cache_destroy(nfs_page_cachep)) 396 printk(KERN_INFO "nfs_page: not all structures were freed\n"); 397 } 398 399