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/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> 21 22 #include "internal.h" 23 24 static struct kmem_cache *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, GFP_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. 54 * User should ensure it is safe to sleep in this function. 55 */ 56 struct nfs_page * 57 nfs_create_request(struct nfs_open_context *ctx, struct inode *inode, 58 struct page *page, 59 unsigned int offset, unsigned int count) 60 { 61 struct nfs_server *server = NFS_SERVER(inode); 62 struct nfs_page *req; 63 64 for (;;) { 65 /* try to allocate the request struct */ 66 req = nfs_page_alloc(); 67 if (req != NULL) 68 break; 69 70 if (signalled() && (server->flags & NFS_MOUNT_INTR)) 71 return ERR_PTR(-ERESTARTSYS); 72 yield(); 73 } 74 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. */ 78 req->wb_page = page; 79 atomic_set(&req->wb_complete, 0); 80 req->wb_index = page->index; 81 page_cache_get(page); 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 atomic_set(&req->wb_count, 1); 89 req->wb_context = get_nfs_open_context(ctx); 90 91 return req; 92 } 93 94 /** 95 * nfs_unlock_request - Unlock request and wake up sleepers. 96 * @req: 97 */ 98 void nfs_unlock_request(struct nfs_page *req) 99 { 100 if (!NFS_WBACK_BUSY(req)) { 101 printk(KERN_ERR "NFS: Invalid unlock attempted\n"); 102 BUG(); 103 } 104 smp_mb__before_clear_bit(); 105 clear_bit(PG_BUSY, &req->wb_flags); 106 smp_mb__after_clear_bit(); 107 wake_up_bit(&req->wb_flags, PG_BUSY); 108 nfs_release_request(req); 109 } 110 111 /** 112 * nfs_set_page_writeback_locked - Lock a request for writeback 113 * @req: 114 */ 115 int nfs_set_page_writeback_locked(struct nfs_page *req) 116 { 117 struct nfs_inode *nfsi = NFS_I(req->wb_context->dentry->d_inode); 118 119 if (!nfs_lock_request(req)) 120 return 0; 121 radix_tree_tag_set(&nfsi->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_WRITEBACK); 122 return 1; 123 } 124 125 /** 126 * nfs_clear_page_writeback - Unlock request and wake up sleepers 127 */ 128 void nfs_clear_page_writeback(struct nfs_page *req) 129 { 130 struct nfs_inode *nfsi = NFS_I(req->wb_context->dentry->d_inode); 131 132 if (req->wb_page != NULL) { 133 spin_lock(&nfsi->req_lock); 134 radix_tree_tag_clear(&nfsi->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_WRITEBACK); 135 spin_unlock(&nfsi->req_lock); 136 } 137 nfs_unlock_request(req); 138 } 139 140 /** 141 * nfs_clear_request - Free up all resources allocated to the request 142 * @req: 143 * 144 * Release page resources associated with a write request after it 145 * has completed. 146 */ 147 void nfs_clear_request(struct nfs_page *req) 148 { 149 struct page *page = req->wb_page; 150 if (page != NULL) { 151 page_cache_release(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 /* Release struct file or cached credential */ 170 nfs_clear_request(req); 171 put_nfs_open_context(req->wb_context); 172 nfs_page_free(req); 173 } 174 175 static int nfs_wait_bit_interruptible(void *word) 176 { 177 int ret = 0; 178 179 if (signal_pending(current)) 180 ret = -ERESTARTSYS; 181 else 182 schedule(); 183 return ret; 184 } 185 186 /** 187 * nfs_wait_on_request - Wait for a request to complete. 188 * @req: request to wait upon. 189 * 190 * Interruptible by signals only if mounted with intr flag. 191 * The user is responsible for holding a count on the request. 192 */ 193 int 194 nfs_wait_on_request(struct nfs_page *req) 195 { 196 struct rpc_clnt *clnt = NFS_CLIENT(req->wb_context->dentry->d_inode); 197 sigset_t oldmask; 198 int ret = 0; 199 200 if (!test_bit(PG_BUSY, &req->wb_flags)) 201 goto out; 202 /* 203 * Note: the call to rpc_clnt_sigmask() suffices to ensure that we 204 * are not interrupted if intr flag is not set 205 */ 206 rpc_clnt_sigmask(clnt, &oldmask); 207 ret = out_of_line_wait_on_bit(&req->wb_flags, PG_BUSY, 208 nfs_wait_bit_interruptible, TASK_INTERRUPTIBLE); 209 rpc_clnt_sigunmask(clnt, &oldmask); 210 out: 211 return ret; 212 } 213 214 /** 215 * nfs_pageio_init - initialise a page io descriptor 216 * @desc: pointer to descriptor 217 * @inode: pointer to inode 218 * @doio: pointer to io function 219 * @bsize: io block size 220 * @io_flags: extra parameters for the io function 221 */ 222 void nfs_pageio_init(struct nfs_pageio_descriptor *desc, 223 struct inode *inode, 224 int (*doio)(struct inode *, struct list_head *, unsigned int, size_t, int), 225 size_t bsize, 226 int io_flags) 227 { 228 INIT_LIST_HEAD(&desc->pg_list); 229 desc->pg_bytes_written = 0; 230 desc->pg_count = 0; 231 desc->pg_bsize = bsize; 232 desc->pg_base = 0; 233 desc->pg_inode = inode; 234 desc->pg_doio = doio; 235 desc->pg_ioflags = io_flags; 236 desc->pg_error = 0; 237 } 238 239 /** 240 * nfs_can_coalesce_requests - test two requests for compatibility 241 * @prev: pointer to nfs_page 242 * @req: pointer to nfs_page 243 * 244 * The nfs_page structures 'prev' and 'req' are compared to ensure that the 245 * page data area they describe is contiguous, and that their RPC 246 * credentials, NFSv4 open state, and lockowners are the same. 247 * 248 * Return 'true' if this is the case, else return 'false'. 249 */ 250 static int nfs_can_coalesce_requests(struct nfs_page *prev, 251 struct nfs_page *req) 252 { 253 if (req->wb_context->cred != prev->wb_context->cred) 254 return 0; 255 if (req->wb_context->lockowner != prev->wb_context->lockowner) 256 return 0; 257 if (req->wb_context->state != prev->wb_context->state) 258 return 0; 259 if (req->wb_index != (prev->wb_index + 1)) 260 return 0; 261 if (req->wb_pgbase != 0) 262 return 0; 263 if (prev->wb_pgbase + prev->wb_bytes != PAGE_CACHE_SIZE) 264 return 0; 265 return 1; 266 } 267 268 /** 269 * nfs_pageio_do_add_request - Attempt to coalesce a request into a page list. 270 * @desc: destination io descriptor 271 * @req: request 272 * 273 * Returns true if the request 'req' was successfully coalesced into the 274 * existing list of pages 'desc'. 275 */ 276 static int nfs_pageio_do_add_request(struct nfs_pageio_descriptor *desc, 277 struct nfs_page *req) 278 { 279 size_t newlen = req->wb_bytes; 280 281 if (desc->pg_count != 0) { 282 struct nfs_page *prev; 283 284 /* 285 * FIXME: ideally we should be able to coalesce all requests 286 * that are not block boundary aligned, but currently this 287 * is problematic for the case of bsize < PAGE_CACHE_SIZE, 288 * since nfs_flush_multi and nfs_pagein_multi assume you 289 * can have only one struct nfs_page. 290 */ 291 if (desc->pg_bsize < PAGE_SIZE) 292 return 0; 293 newlen += desc->pg_count; 294 if (newlen > desc->pg_bsize) 295 return 0; 296 prev = nfs_list_entry(desc->pg_list.prev); 297 if (!nfs_can_coalesce_requests(prev, req)) 298 return 0; 299 } else 300 desc->pg_base = req->wb_pgbase; 301 nfs_list_remove_request(req); 302 nfs_list_add_request(req, &desc->pg_list); 303 desc->pg_count = newlen; 304 return 1; 305 } 306 307 /* 308 * Helper for nfs_pageio_add_request and nfs_pageio_complete 309 */ 310 static void nfs_pageio_doio(struct nfs_pageio_descriptor *desc) 311 { 312 if (!list_empty(&desc->pg_list)) { 313 int error = desc->pg_doio(desc->pg_inode, 314 &desc->pg_list, 315 nfs_page_array_len(desc->pg_base, 316 desc->pg_count), 317 desc->pg_count, 318 desc->pg_ioflags); 319 if (error < 0) 320 desc->pg_error = error; 321 else 322 desc->pg_bytes_written += desc->pg_count; 323 } 324 if (list_empty(&desc->pg_list)) { 325 desc->pg_count = 0; 326 desc->pg_base = 0; 327 } 328 } 329 330 /** 331 * nfs_pageio_add_request - Attempt to coalesce a request into a page list. 332 * @desc: destination io descriptor 333 * @req: request 334 * 335 * Returns true if the request 'req' was successfully coalesced into the 336 * existing list of pages 'desc'. 337 */ 338 int nfs_pageio_add_request(struct nfs_pageio_descriptor *desc, 339 struct nfs_page *req) 340 { 341 while (!nfs_pageio_do_add_request(desc, req)) { 342 nfs_pageio_doio(desc); 343 if (desc->pg_error < 0) 344 return 0; 345 } 346 return 1; 347 } 348 349 /** 350 * nfs_pageio_complete - Complete I/O on an nfs_pageio_descriptor 351 * @desc: pointer to io descriptor 352 */ 353 void nfs_pageio_complete(struct nfs_pageio_descriptor *desc) 354 { 355 nfs_pageio_doio(desc); 356 } 357 358 /** 359 * nfs_pageio_cond_complete - Conditional I/O completion 360 * @desc: pointer to io descriptor 361 * @index: page index 362 * 363 * It is important to ensure that processes don't try to take locks 364 * on non-contiguous ranges of pages as that might deadlock. This 365 * function should be called before attempting to wait on a locked 366 * nfs_page. It will complete the I/O if the page index 'index' 367 * is not contiguous with the existing list of pages in 'desc'. 368 */ 369 void nfs_pageio_cond_complete(struct nfs_pageio_descriptor *desc, pgoff_t index) 370 { 371 if (!list_empty(&desc->pg_list)) { 372 struct nfs_page *prev = nfs_list_entry(desc->pg_list.prev); 373 if (index != prev->wb_index + 1) 374 nfs_pageio_doio(desc); 375 } 376 } 377 378 #define NFS_SCAN_MAXENTRIES 16 379 /** 380 * nfs_scan_list - Scan a list for matching requests 381 * @nfsi: NFS inode 382 * @head: One of the NFS inode request lists 383 * @dst: Destination list 384 * @idx_start: lower bound of page->index to scan 385 * @npages: idx_start + npages sets the upper bound to scan. 386 * 387 * Moves elements from one of the inode request lists. 388 * If the number of requests is set to 0, the entire address_space 389 * starting at index idx_start, is scanned. 390 * The requests are *not* checked to ensure that they form a contiguous set. 391 * You must be holding the inode's req_lock when calling this function 392 */ 393 int nfs_scan_list(struct nfs_inode *nfsi, struct list_head *head, 394 struct list_head *dst, pgoff_t idx_start, 395 unsigned int npages) 396 { 397 struct nfs_page *pgvec[NFS_SCAN_MAXENTRIES]; 398 struct nfs_page *req; 399 pgoff_t idx_end; 400 int found, i; 401 int res; 402 403 res = 0; 404 if (npages == 0) 405 idx_end = ~0; 406 else 407 idx_end = idx_start + npages - 1; 408 409 for (;;) { 410 found = radix_tree_gang_lookup(&nfsi->nfs_page_tree, 411 (void **)&pgvec[0], idx_start, 412 NFS_SCAN_MAXENTRIES); 413 if (found <= 0) 414 break; 415 for (i = 0; i < found; i++) { 416 req = pgvec[i]; 417 if (req->wb_index > idx_end) 418 goto out; 419 idx_start = req->wb_index + 1; 420 if (req->wb_list_head != head) 421 continue; 422 if (nfs_set_page_writeback_locked(req)) { 423 nfs_list_remove_request(req); 424 nfs_list_add_request(req, dst); 425 res++; 426 } 427 } 428 429 } 430 out: 431 return res; 432 } 433 434 int __init nfs_init_nfspagecache(void) 435 { 436 nfs_page_cachep = kmem_cache_create("nfs_page", 437 sizeof(struct nfs_page), 438 0, SLAB_HWCACHE_ALIGN, 439 NULL, NULL); 440 if (nfs_page_cachep == NULL) 441 return -ENOMEM; 442 443 return 0; 444 } 445 446 void nfs_destroy_nfspagecache(void) 447 { 448 kmem_cache_destroy(nfs_page_cachep); 449 } 450 451