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_page *req; 62 63 for (;;) { 64 /* try to allocate the request struct */ 65 req = nfs_page_alloc(); 66 if (req != NULL) 67 break; 68 69 if (fatal_signal_pending(current)) 70 return ERR_PTR(-ERESTARTSYS); 71 yield(); 72 } 73 74 /* Initialize the request struct. Initially, we assume a 75 * long write-back delay. This will be adjusted in 76 * update_nfs_request below if the region is not locked. */ 77 req->wb_page = page; 78 atomic_set(&req->wb_complete, 0); 79 req->wb_index = page->index; 80 page_cache_get(page); 81 BUG_ON(PagePrivate(page)); 82 BUG_ON(!PageLocked(page)); 83 BUG_ON(page->mapping->host != inode); 84 req->wb_offset = offset; 85 req->wb_pgbase = offset; 86 req->wb_bytes = count; 87 req->wb_context = get_nfs_open_context(ctx); 88 kref_init(&req->wb_kref); 89 return req; 90 } 91 92 /** 93 * nfs_unlock_request - Unlock request and wake up sleepers. 94 * @req: 95 */ 96 void nfs_unlock_request(struct nfs_page *req) 97 { 98 if (!NFS_WBACK_BUSY(req)) { 99 printk(KERN_ERR "NFS: Invalid unlock attempted\n"); 100 BUG(); 101 } 102 smp_mb__before_clear_bit(); 103 clear_bit(PG_BUSY, &req->wb_flags); 104 smp_mb__after_clear_bit(); 105 wake_up_bit(&req->wb_flags, PG_BUSY); 106 nfs_release_request(req); 107 } 108 109 /** 110 * nfs_set_page_tag_locked - Tag a request as locked 111 * @req: 112 */ 113 int nfs_set_page_tag_locked(struct nfs_page *req) 114 { 115 struct nfs_inode *nfsi = NFS_I(req->wb_context->path.dentry->d_inode); 116 117 if (!nfs_lock_request_dontget(req)) 118 return 0; 119 if (req->wb_page != NULL) 120 radix_tree_tag_set(&nfsi->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_LOCKED); 121 return 1; 122 } 123 124 /** 125 * nfs_clear_page_tag_locked - Clear request tag and wake up sleepers 126 */ 127 void nfs_clear_page_tag_locked(struct nfs_page *req) 128 { 129 struct inode *inode = req->wb_context->path.dentry->d_inode; 130 struct nfs_inode *nfsi = NFS_I(inode); 131 132 if (req->wb_page != NULL) { 133 spin_lock(&inode->i_lock); 134 radix_tree_tag_clear(&nfsi->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_LOCKED); 135 nfs_unlock_request(req); 136 spin_unlock(&inode->i_lock); 137 } else 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 struct page *page = req->wb_page; 151 if (page != NULL) { 152 page_cache_release(page); 153 req->wb_page = NULL; 154 } 155 } 156 157 158 /** 159 * nfs_release_request - Release the count on an NFS read/write request 160 * @req: request to release 161 * 162 * Note: Should never be called with the spinlock held! 163 */ 164 static void nfs_free_request(struct kref *kref) 165 { 166 struct nfs_page *req = container_of(kref, struct nfs_page, wb_kref); 167 168 /* Release struct file or cached credential */ 169 nfs_clear_request(req); 170 put_nfs_open_context(req->wb_context); 171 nfs_page_free(req); 172 } 173 174 void nfs_release_request(struct nfs_page *req) 175 { 176 kref_put(&req->wb_kref, nfs_free_request); 177 } 178 179 static int nfs_wait_bit_uninterruptible(void *word) 180 { 181 io_schedule(); 182 return 0; 183 } 184 185 /** 186 * nfs_wait_on_request - Wait for a request to complete. 187 * @req: request to wait upon. 188 * 189 * Interruptible by fatal signals only. 190 * The user is responsible for holding a count on the request. 191 */ 192 int 193 nfs_wait_on_request(struct nfs_page *req) 194 { 195 return wait_on_bit(&req->wb_flags, PG_BUSY, 196 nfs_wait_bit_uninterruptible, 197 TASK_UNINTERRUPTIBLE); 198 } 199 200 /** 201 * nfs_pageio_init - initialise a page io descriptor 202 * @desc: pointer to descriptor 203 * @inode: pointer to inode 204 * @doio: pointer to io function 205 * @bsize: io block size 206 * @io_flags: extra parameters for the io function 207 */ 208 void nfs_pageio_init(struct nfs_pageio_descriptor *desc, 209 struct inode *inode, 210 int (*doio)(struct inode *, struct list_head *, unsigned int, size_t, int), 211 size_t bsize, 212 int io_flags) 213 { 214 INIT_LIST_HEAD(&desc->pg_list); 215 desc->pg_bytes_written = 0; 216 desc->pg_count = 0; 217 desc->pg_bsize = bsize; 218 desc->pg_base = 0; 219 desc->pg_inode = inode; 220 desc->pg_doio = doio; 221 desc->pg_ioflags = io_flags; 222 desc->pg_error = 0; 223 } 224 225 /** 226 * nfs_can_coalesce_requests - test two requests for compatibility 227 * @prev: pointer to nfs_page 228 * @req: pointer to nfs_page 229 * 230 * The nfs_page structures 'prev' and 'req' are compared to ensure that the 231 * page data area they describe is contiguous, and that their RPC 232 * credentials, NFSv4 open state, and lockowners are the same. 233 * 234 * Return 'true' if this is the case, else return 'false'. 235 */ 236 static int nfs_can_coalesce_requests(struct nfs_page *prev, 237 struct nfs_page *req) 238 { 239 if (req->wb_context->cred != prev->wb_context->cred) 240 return 0; 241 if (req->wb_context->lockowner != prev->wb_context->lockowner) 242 return 0; 243 if (req->wb_context->state != prev->wb_context->state) 244 return 0; 245 if (req->wb_index != (prev->wb_index + 1)) 246 return 0; 247 if (req->wb_pgbase != 0) 248 return 0; 249 if (prev->wb_pgbase + prev->wb_bytes != PAGE_CACHE_SIZE) 250 return 0; 251 return 1; 252 } 253 254 /** 255 * nfs_pageio_do_add_request - Attempt to coalesce a request into a page list. 256 * @desc: destination io descriptor 257 * @req: request 258 * 259 * Returns true if the request 'req' was successfully coalesced into the 260 * existing list of pages 'desc'. 261 */ 262 static int nfs_pageio_do_add_request(struct nfs_pageio_descriptor *desc, 263 struct nfs_page *req) 264 { 265 size_t newlen = req->wb_bytes; 266 267 if (desc->pg_count != 0) { 268 struct nfs_page *prev; 269 270 /* 271 * FIXME: ideally we should be able to coalesce all requests 272 * that are not block boundary aligned, but currently this 273 * is problematic for the case of bsize < PAGE_CACHE_SIZE, 274 * since nfs_flush_multi and nfs_pagein_multi assume you 275 * can have only one struct nfs_page. 276 */ 277 if (desc->pg_bsize < PAGE_SIZE) 278 return 0; 279 newlen += desc->pg_count; 280 if (newlen > desc->pg_bsize) 281 return 0; 282 prev = nfs_list_entry(desc->pg_list.prev); 283 if (!nfs_can_coalesce_requests(prev, req)) 284 return 0; 285 } else 286 desc->pg_base = req->wb_pgbase; 287 nfs_list_remove_request(req); 288 nfs_list_add_request(req, &desc->pg_list); 289 desc->pg_count = newlen; 290 return 1; 291 } 292 293 /* 294 * Helper for nfs_pageio_add_request and nfs_pageio_complete 295 */ 296 static void nfs_pageio_doio(struct nfs_pageio_descriptor *desc) 297 { 298 if (!list_empty(&desc->pg_list)) { 299 int error = desc->pg_doio(desc->pg_inode, 300 &desc->pg_list, 301 nfs_page_array_len(desc->pg_base, 302 desc->pg_count), 303 desc->pg_count, 304 desc->pg_ioflags); 305 if (error < 0) 306 desc->pg_error = error; 307 else 308 desc->pg_bytes_written += desc->pg_count; 309 } 310 if (list_empty(&desc->pg_list)) { 311 desc->pg_count = 0; 312 desc->pg_base = 0; 313 } 314 } 315 316 /** 317 * nfs_pageio_add_request - Attempt to coalesce a request into a page list. 318 * @desc: destination io descriptor 319 * @req: request 320 * 321 * Returns true if the request 'req' was successfully coalesced into the 322 * existing list of pages 'desc'. 323 */ 324 int nfs_pageio_add_request(struct nfs_pageio_descriptor *desc, 325 struct nfs_page *req) 326 { 327 while (!nfs_pageio_do_add_request(desc, req)) { 328 nfs_pageio_doio(desc); 329 if (desc->pg_error < 0) 330 return 0; 331 } 332 return 1; 333 } 334 335 /** 336 * nfs_pageio_complete - Complete I/O on an nfs_pageio_descriptor 337 * @desc: pointer to io descriptor 338 */ 339 void nfs_pageio_complete(struct nfs_pageio_descriptor *desc) 340 { 341 nfs_pageio_doio(desc); 342 } 343 344 /** 345 * nfs_pageio_cond_complete - Conditional I/O completion 346 * @desc: pointer to io descriptor 347 * @index: page index 348 * 349 * It is important to ensure that processes don't try to take locks 350 * on non-contiguous ranges of pages as that might deadlock. This 351 * function should be called before attempting to wait on a locked 352 * nfs_page. It will complete the I/O if the page index 'index' 353 * is not contiguous with the existing list of pages in 'desc'. 354 */ 355 void nfs_pageio_cond_complete(struct nfs_pageio_descriptor *desc, pgoff_t index) 356 { 357 if (!list_empty(&desc->pg_list)) { 358 struct nfs_page *prev = nfs_list_entry(desc->pg_list.prev); 359 if (index != prev->wb_index + 1) 360 nfs_pageio_doio(desc); 361 } 362 } 363 364 #define NFS_SCAN_MAXENTRIES 16 365 /** 366 * nfs_scan_list - Scan a list for matching requests 367 * @nfsi: NFS inode 368 * @dst: Destination list 369 * @idx_start: lower bound of page->index to scan 370 * @npages: idx_start + npages sets the upper bound to scan. 371 * @tag: tag to scan for 372 * 373 * Moves elements from one of the inode request lists. 374 * If the number of requests is set to 0, the entire address_space 375 * starting at index idx_start, is scanned. 376 * The requests are *not* checked to ensure that they form a contiguous set. 377 * You must be holding the inode's i_lock when calling this function 378 */ 379 int nfs_scan_list(struct nfs_inode *nfsi, 380 struct list_head *dst, pgoff_t idx_start, 381 unsigned int npages, int tag) 382 { 383 struct nfs_page *pgvec[NFS_SCAN_MAXENTRIES]; 384 struct nfs_page *req; 385 pgoff_t idx_end; 386 int found, i; 387 int res; 388 389 res = 0; 390 if (npages == 0) 391 idx_end = ~0; 392 else 393 idx_end = idx_start + npages - 1; 394 395 for (;;) { 396 found = radix_tree_gang_lookup_tag(&nfsi->nfs_page_tree, 397 (void **)&pgvec[0], idx_start, 398 NFS_SCAN_MAXENTRIES, tag); 399 if (found <= 0) 400 break; 401 for (i = 0; i < found; i++) { 402 req = pgvec[i]; 403 if (req->wb_index > idx_end) 404 goto out; 405 idx_start = req->wb_index + 1; 406 if (nfs_set_page_tag_locked(req)) { 407 kref_get(&req->wb_kref); 408 nfs_list_remove_request(req); 409 radix_tree_tag_clear(&nfsi->nfs_page_tree, 410 req->wb_index, tag); 411 nfs_list_add_request(req, dst); 412 res++; 413 if (res == INT_MAX) 414 goto out; 415 } 416 } 417 /* for latency reduction */ 418 cond_resched_lock(&nfsi->vfs_inode.i_lock); 419 } 420 out: 421 return res; 422 } 423 424 int __init nfs_init_nfspagecache(void) 425 { 426 nfs_page_cachep = kmem_cache_create("nfs_page", 427 sizeof(struct nfs_page), 428 0, SLAB_HWCACHE_ALIGN, 429 NULL); 430 if (nfs_page_cachep == NULL) 431 return -ENOMEM; 432 433 return 0; 434 } 435 436 void nfs_destroy_nfspagecache(void) 437 { 438 kmem_cache_destroy(nfs_page_cachep); 439 } 440 441