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 /** 180 * nfs_wait_on_request - Wait for a request to complete. 181 * @req: request to wait upon. 182 * 183 * Interruptible by fatal signals only. 184 * The user is responsible for holding a count on the request. 185 */ 186 int 187 nfs_wait_on_request(struct nfs_page *req) 188 { 189 int ret = 0; 190 191 if (!test_bit(PG_BUSY, &req->wb_flags)) 192 goto out; 193 ret = out_of_line_wait_on_bit(&req->wb_flags, PG_BUSY, 194 nfs_wait_bit_killable, TASK_KILLABLE); 195 out: 196 return ret; 197 } 198 199 /** 200 * nfs_pageio_init - initialise a page io descriptor 201 * @desc: pointer to descriptor 202 * @inode: pointer to inode 203 * @doio: pointer to io function 204 * @bsize: io block size 205 * @io_flags: extra parameters for the io function 206 */ 207 void nfs_pageio_init(struct nfs_pageio_descriptor *desc, 208 struct inode *inode, 209 int (*doio)(struct inode *, struct list_head *, unsigned int, size_t, int), 210 size_t bsize, 211 int io_flags) 212 { 213 INIT_LIST_HEAD(&desc->pg_list); 214 desc->pg_bytes_written = 0; 215 desc->pg_count = 0; 216 desc->pg_bsize = bsize; 217 desc->pg_base = 0; 218 desc->pg_inode = inode; 219 desc->pg_doio = doio; 220 desc->pg_ioflags = io_flags; 221 desc->pg_error = 0; 222 } 223 224 /** 225 * nfs_can_coalesce_requests - test two requests for compatibility 226 * @prev: pointer to nfs_page 227 * @req: pointer to nfs_page 228 * 229 * The nfs_page structures 'prev' and 'req' are compared to ensure that the 230 * page data area they describe is contiguous, and that their RPC 231 * credentials, NFSv4 open state, and lockowners are the same. 232 * 233 * Return 'true' if this is the case, else return 'false'. 234 */ 235 static int nfs_can_coalesce_requests(struct nfs_page *prev, 236 struct nfs_page *req) 237 { 238 if (req->wb_context->cred != prev->wb_context->cred) 239 return 0; 240 if (req->wb_context->lockowner != prev->wb_context->lockowner) 241 return 0; 242 if (req->wb_context->state != prev->wb_context->state) 243 return 0; 244 if (req->wb_index != (prev->wb_index + 1)) 245 return 0; 246 if (req->wb_pgbase != 0) 247 return 0; 248 if (prev->wb_pgbase + prev->wb_bytes != PAGE_CACHE_SIZE) 249 return 0; 250 return 1; 251 } 252 253 /** 254 * nfs_pageio_do_add_request - Attempt to coalesce a request into a page list. 255 * @desc: destination io descriptor 256 * @req: request 257 * 258 * Returns true if the request 'req' was successfully coalesced into the 259 * existing list of pages 'desc'. 260 */ 261 static int nfs_pageio_do_add_request(struct nfs_pageio_descriptor *desc, 262 struct nfs_page *req) 263 { 264 size_t newlen = req->wb_bytes; 265 266 if (desc->pg_count != 0) { 267 struct nfs_page *prev; 268 269 /* 270 * FIXME: ideally we should be able to coalesce all requests 271 * that are not block boundary aligned, but currently this 272 * is problematic for the case of bsize < PAGE_CACHE_SIZE, 273 * since nfs_flush_multi and nfs_pagein_multi assume you 274 * can have only one struct nfs_page. 275 */ 276 if (desc->pg_bsize < PAGE_SIZE) 277 return 0; 278 newlen += desc->pg_count; 279 if (newlen > desc->pg_bsize) 280 return 0; 281 prev = nfs_list_entry(desc->pg_list.prev); 282 if (!nfs_can_coalesce_requests(prev, req)) 283 return 0; 284 } else 285 desc->pg_base = req->wb_pgbase; 286 nfs_list_remove_request(req); 287 nfs_list_add_request(req, &desc->pg_list); 288 desc->pg_count = newlen; 289 return 1; 290 } 291 292 /* 293 * Helper for nfs_pageio_add_request and nfs_pageio_complete 294 */ 295 static void nfs_pageio_doio(struct nfs_pageio_descriptor *desc) 296 { 297 if (!list_empty(&desc->pg_list)) { 298 int error = desc->pg_doio(desc->pg_inode, 299 &desc->pg_list, 300 nfs_page_array_len(desc->pg_base, 301 desc->pg_count), 302 desc->pg_count, 303 desc->pg_ioflags); 304 if (error < 0) 305 desc->pg_error = error; 306 else 307 desc->pg_bytes_written += desc->pg_count; 308 } 309 if (list_empty(&desc->pg_list)) { 310 desc->pg_count = 0; 311 desc->pg_base = 0; 312 } 313 } 314 315 /** 316 * nfs_pageio_add_request - Attempt to coalesce a request into a page list. 317 * @desc: destination io descriptor 318 * @req: request 319 * 320 * Returns true if the request 'req' was successfully coalesced into the 321 * existing list of pages 'desc'. 322 */ 323 int nfs_pageio_add_request(struct nfs_pageio_descriptor *desc, 324 struct nfs_page *req) 325 { 326 while (!nfs_pageio_do_add_request(desc, req)) { 327 nfs_pageio_doio(desc); 328 if (desc->pg_error < 0) 329 return 0; 330 } 331 return 1; 332 } 333 334 /** 335 * nfs_pageio_complete - Complete I/O on an nfs_pageio_descriptor 336 * @desc: pointer to io descriptor 337 */ 338 void nfs_pageio_complete(struct nfs_pageio_descriptor *desc) 339 { 340 nfs_pageio_doio(desc); 341 } 342 343 /** 344 * nfs_pageio_cond_complete - Conditional I/O completion 345 * @desc: pointer to io descriptor 346 * @index: page index 347 * 348 * It is important to ensure that processes don't try to take locks 349 * on non-contiguous ranges of pages as that might deadlock. This 350 * function should be called before attempting to wait on a locked 351 * nfs_page. It will complete the I/O if the page index 'index' 352 * is not contiguous with the existing list of pages in 'desc'. 353 */ 354 void nfs_pageio_cond_complete(struct nfs_pageio_descriptor *desc, pgoff_t index) 355 { 356 if (!list_empty(&desc->pg_list)) { 357 struct nfs_page *prev = nfs_list_entry(desc->pg_list.prev); 358 if (index != prev->wb_index + 1) 359 nfs_pageio_doio(desc); 360 } 361 } 362 363 #define NFS_SCAN_MAXENTRIES 16 364 /** 365 * nfs_scan_list - Scan a list for matching requests 366 * @nfsi: NFS inode 367 * @dst: Destination list 368 * @idx_start: lower bound of page->index to scan 369 * @npages: idx_start + npages sets the upper bound to scan. 370 * @tag: tag to scan for 371 * 372 * Moves elements from one of the inode request lists. 373 * If the number of requests is set to 0, the entire address_space 374 * starting at index idx_start, is scanned. 375 * The requests are *not* checked to ensure that they form a contiguous set. 376 * You must be holding the inode's i_lock when calling this function 377 */ 378 int nfs_scan_list(struct nfs_inode *nfsi, 379 struct list_head *dst, pgoff_t idx_start, 380 unsigned int npages, int tag) 381 { 382 struct nfs_page *pgvec[NFS_SCAN_MAXENTRIES]; 383 struct nfs_page *req; 384 pgoff_t idx_end; 385 int found, i; 386 int res; 387 388 res = 0; 389 if (npages == 0) 390 idx_end = ~0; 391 else 392 idx_end = idx_start + npages - 1; 393 394 for (;;) { 395 found = radix_tree_gang_lookup_tag(&nfsi->nfs_page_tree, 396 (void **)&pgvec[0], idx_start, 397 NFS_SCAN_MAXENTRIES, tag); 398 if (found <= 0) 399 break; 400 for (i = 0; i < found; i++) { 401 req = pgvec[i]; 402 if (req->wb_index > idx_end) 403 goto out; 404 idx_start = req->wb_index + 1; 405 if (nfs_set_page_tag_locked(req)) { 406 kref_get(&req->wb_kref); 407 nfs_list_remove_request(req); 408 radix_tree_tag_clear(&nfsi->nfs_page_tree, 409 req->wb_index, tag); 410 nfs_list_add_request(req, dst); 411 res++; 412 if (res == INT_MAX) 413 goto out; 414 } 415 } 416 /* for latency reduction */ 417 cond_resched_lock(&nfsi->vfs_inode.i_lock); 418 } 419 out: 420 return res; 421 } 422 423 int __init nfs_init_nfspagecache(void) 424 { 425 nfs_page_cachep = kmem_cache_create("nfs_page", 426 sizeof(struct nfs_page), 427 0, SLAB_HWCACHE_ALIGN, 428 NULL); 429 if (nfs_page_cachep == NULL) 430 return -ENOMEM; 431 432 return 0; 433 } 434 435 void nfs_destroy_nfspagecache(void) 436 { 437 kmem_cache_destroy(nfs_page_cachep); 438 } 439 440