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 /* try to allocate the request struct */ 64 req = nfs_page_alloc(); 65 if (req == NULL) 66 return ERR_PTR(-ENOMEM); 67 68 /* Initialize the request struct. Initially, we assume a 69 * long write-back delay. This will be adjusted in 70 * update_nfs_request below if the region is not locked. */ 71 req->wb_page = page; 72 atomic_set(&req->wb_complete, 0); 73 req->wb_index = page->index; 74 page_cache_get(page); 75 BUG_ON(PagePrivate(page)); 76 BUG_ON(!PageLocked(page)); 77 BUG_ON(page->mapping->host != inode); 78 req->wb_offset = offset; 79 req->wb_pgbase = offset; 80 req->wb_bytes = count; 81 req->wb_context = get_nfs_open_context(ctx); 82 kref_init(&req->wb_kref); 83 return req; 84 } 85 86 /** 87 * nfs_unlock_request - Unlock request and wake up sleepers. 88 * @req: 89 */ 90 void nfs_unlock_request(struct nfs_page *req) 91 { 92 if (!NFS_WBACK_BUSY(req)) { 93 printk(KERN_ERR "NFS: Invalid unlock attempted\n"); 94 BUG(); 95 } 96 smp_mb__before_clear_bit(); 97 clear_bit(PG_BUSY, &req->wb_flags); 98 smp_mb__after_clear_bit(); 99 wake_up_bit(&req->wb_flags, PG_BUSY); 100 nfs_release_request(req); 101 } 102 103 /** 104 * nfs_set_page_tag_locked - Tag a request as locked 105 * @req: 106 */ 107 int nfs_set_page_tag_locked(struct nfs_page *req) 108 { 109 if (!nfs_lock_request_dontget(req)) 110 return 0; 111 if (req->wb_page != NULL) 112 radix_tree_tag_set(&NFS_I(req->wb_context->path.dentry->d_inode)->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_LOCKED); 113 return 1; 114 } 115 116 /** 117 * nfs_clear_page_tag_locked - Clear request tag and wake up sleepers 118 */ 119 void nfs_clear_page_tag_locked(struct nfs_page *req) 120 { 121 if (req->wb_page != NULL) { 122 struct inode *inode = req->wb_context->path.dentry->d_inode; 123 struct nfs_inode *nfsi = NFS_I(inode); 124 125 spin_lock(&inode->i_lock); 126 radix_tree_tag_clear(&nfsi->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_LOCKED); 127 nfs_unlock_request(req); 128 spin_unlock(&inode->i_lock); 129 } else 130 nfs_unlock_request(req); 131 } 132 133 /** 134 * nfs_clear_request - Free up all resources allocated to the request 135 * @req: 136 * 137 * Release page and open context resources associated with a read/write 138 * request after it has completed. 139 */ 140 void nfs_clear_request(struct nfs_page *req) 141 { 142 struct page *page = req->wb_page; 143 struct nfs_open_context *ctx = req->wb_context; 144 145 if (page != NULL) { 146 page_cache_release(page); 147 req->wb_page = NULL; 148 } 149 if (ctx != NULL) { 150 put_nfs_open_context(ctx); 151 req->wb_context = NULL; 152 } 153 } 154 155 156 /** 157 * nfs_release_request - Release the count on an NFS read/write request 158 * @req: request to release 159 * 160 * Note: Should never be called with the spinlock held! 161 */ 162 static void nfs_free_request(struct kref *kref) 163 { 164 struct nfs_page *req = container_of(kref, struct nfs_page, wb_kref); 165 166 /* Release struct file and open context */ 167 nfs_clear_request(req); 168 nfs_page_free(req); 169 } 170 171 void nfs_release_request(struct nfs_page *req) 172 { 173 kref_put(&req->wb_kref, nfs_free_request); 174 } 175 176 static int nfs_wait_bit_uninterruptible(void *word) 177 { 178 io_schedule(); 179 return 0; 180 } 181 182 /** 183 * nfs_wait_on_request - Wait for a request to complete. 184 * @req: request to wait upon. 185 * 186 * Interruptible by fatal signals only. 187 * The user is responsible for holding a count on the request. 188 */ 189 int 190 nfs_wait_on_request(struct nfs_page *req) 191 { 192 return wait_on_bit(&req->wb_flags, PG_BUSY, 193 nfs_wait_bit_uninterruptible, 194 TASK_UNINTERRUPTIBLE); 195 } 196 197 /** 198 * nfs_pageio_init - initialise a page io descriptor 199 * @desc: pointer to descriptor 200 * @inode: pointer to inode 201 * @doio: pointer to io function 202 * @bsize: io block size 203 * @io_flags: extra parameters for the io function 204 */ 205 void nfs_pageio_init(struct nfs_pageio_descriptor *desc, 206 struct inode *inode, 207 int (*doio)(struct inode *, struct list_head *, unsigned int, size_t, int), 208 size_t bsize, 209 int io_flags) 210 { 211 INIT_LIST_HEAD(&desc->pg_list); 212 desc->pg_bytes_written = 0; 213 desc->pg_count = 0; 214 desc->pg_bsize = bsize; 215 desc->pg_base = 0; 216 desc->pg_inode = inode; 217 desc->pg_doio = doio; 218 desc->pg_ioflags = io_flags; 219 desc->pg_error = 0; 220 } 221 222 /** 223 * nfs_can_coalesce_requests - test two requests for compatibility 224 * @prev: pointer to nfs_page 225 * @req: pointer to nfs_page 226 * 227 * The nfs_page structures 'prev' and 'req' are compared to ensure that the 228 * page data area they describe is contiguous, and that their RPC 229 * credentials, NFSv4 open state, and lockowners are the same. 230 * 231 * Return 'true' if this is the case, else return 'false'. 232 */ 233 static int nfs_can_coalesce_requests(struct nfs_page *prev, 234 struct nfs_page *req) 235 { 236 if (req->wb_context->cred != prev->wb_context->cred) 237 return 0; 238 if (req->wb_context->lockowner != prev->wb_context->lockowner) 239 return 0; 240 if (req->wb_context->state != prev->wb_context->state) 241 return 0; 242 if (req->wb_index != (prev->wb_index + 1)) 243 return 0; 244 if (req->wb_pgbase != 0) 245 return 0; 246 if (prev->wb_pgbase + prev->wb_bytes != PAGE_CACHE_SIZE) 247 return 0; 248 return 1; 249 } 250 251 /** 252 * nfs_pageio_do_add_request - Attempt to coalesce a request into a page list. 253 * @desc: destination io descriptor 254 * @req: request 255 * 256 * Returns true if the request 'req' was successfully coalesced into the 257 * existing list of pages 'desc'. 258 */ 259 static int nfs_pageio_do_add_request(struct nfs_pageio_descriptor *desc, 260 struct nfs_page *req) 261 { 262 size_t newlen = req->wb_bytes; 263 264 if (desc->pg_count != 0) { 265 struct nfs_page *prev; 266 267 /* 268 * FIXME: ideally we should be able to coalesce all requests 269 * that are not block boundary aligned, but currently this 270 * is problematic for the case of bsize < PAGE_CACHE_SIZE, 271 * since nfs_flush_multi and nfs_pagein_multi assume you 272 * can have only one struct nfs_page. 273 */ 274 if (desc->pg_bsize < PAGE_SIZE) 275 return 0; 276 newlen += desc->pg_count; 277 if (newlen > desc->pg_bsize) 278 return 0; 279 prev = nfs_list_entry(desc->pg_list.prev); 280 if (!nfs_can_coalesce_requests(prev, req)) 281 return 0; 282 } else 283 desc->pg_base = req->wb_pgbase; 284 nfs_list_remove_request(req); 285 nfs_list_add_request(req, &desc->pg_list); 286 desc->pg_count = newlen; 287 return 1; 288 } 289 290 /* 291 * Helper for nfs_pageio_add_request and nfs_pageio_complete 292 */ 293 static void nfs_pageio_doio(struct nfs_pageio_descriptor *desc) 294 { 295 if (!list_empty(&desc->pg_list)) { 296 int error = desc->pg_doio(desc->pg_inode, 297 &desc->pg_list, 298 nfs_page_array_len(desc->pg_base, 299 desc->pg_count), 300 desc->pg_count, 301 desc->pg_ioflags); 302 if (error < 0) 303 desc->pg_error = error; 304 else 305 desc->pg_bytes_written += desc->pg_count; 306 } 307 if (list_empty(&desc->pg_list)) { 308 desc->pg_count = 0; 309 desc->pg_base = 0; 310 } 311 } 312 313 /** 314 * nfs_pageio_add_request - Attempt to coalesce a request into a page list. 315 * @desc: destination io descriptor 316 * @req: request 317 * 318 * Returns true if the request 'req' was successfully coalesced into the 319 * existing list of pages 'desc'. 320 */ 321 int nfs_pageio_add_request(struct nfs_pageio_descriptor *desc, 322 struct nfs_page *req) 323 { 324 while (!nfs_pageio_do_add_request(desc, req)) { 325 nfs_pageio_doio(desc); 326 if (desc->pg_error < 0) 327 return 0; 328 } 329 return 1; 330 } 331 332 /** 333 * nfs_pageio_complete - Complete I/O on an nfs_pageio_descriptor 334 * @desc: pointer to io descriptor 335 */ 336 void nfs_pageio_complete(struct nfs_pageio_descriptor *desc) 337 { 338 nfs_pageio_doio(desc); 339 } 340 341 /** 342 * nfs_pageio_cond_complete - Conditional I/O completion 343 * @desc: pointer to io descriptor 344 * @index: page index 345 * 346 * It is important to ensure that processes don't try to take locks 347 * on non-contiguous ranges of pages as that might deadlock. This 348 * function should be called before attempting to wait on a locked 349 * nfs_page. It will complete the I/O if the page index 'index' 350 * is not contiguous with the existing list of pages in 'desc'. 351 */ 352 void nfs_pageio_cond_complete(struct nfs_pageio_descriptor *desc, pgoff_t index) 353 { 354 if (!list_empty(&desc->pg_list)) { 355 struct nfs_page *prev = nfs_list_entry(desc->pg_list.prev); 356 if (index != prev->wb_index + 1) 357 nfs_pageio_doio(desc); 358 } 359 } 360 361 #define NFS_SCAN_MAXENTRIES 16 362 /** 363 * nfs_scan_list - Scan a list for matching requests 364 * @nfsi: NFS inode 365 * @dst: Destination list 366 * @idx_start: lower bound of page->index to scan 367 * @npages: idx_start + npages sets the upper bound to scan. 368 * @tag: tag to scan for 369 * 370 * Moves elements from one of the inode request lists. 371 * If the number of requests is set to 0, the entire address_space 372 * starting at index idx_start, is scanned. 373 * The requests are *not* checked to ensure that they form a contiguous set. 374 * You must be holding the inode's i_lock when calling this function 375 */ 376 int nfs_scan_list(struct nfs_inode *nfsi, 377 struct list_head *dst, pgoff_t idx_start, 378 unsigned int npages, int tag) 379 { 380 struct nfs_page *pgvec[NFS_SCAN_MAXENTRIES]; 381 struct nfs_page *req; 382 pgoff_t idx_end; 383 int found, i; 384 int res; 385 386 res = 0; 387 if (npages == 0) 388 idx_end = ~0; 389 else 390 idx_end = idx_start + npages - 1; 391 392 for (;;) { 393 found = radix_tree_gang_lookup_tag(&nfsi->nfs_page_tree, 394 (void **)&pgvec[0], idx_start, 395 NFS_SCAN_MAXENTRIES, tag); 396 if (found <= 0) 397 break; 398 for (i = 0; i < found; i++) { 399 req = pgvec[i]; 400 if (req->wb_index > idx_end) 401 goto out; 402 idx_start = req->wb_index + 1; 403 if (nfs_set_page_tag_locked(req)) { 404 kref_get(&req->wb_kref); 405 nfs_list_remove_request(req); 406 radix_tree_tag_clear(&nfsi->nfs_page_tree, 407 req->wb_index, tag); 408 nfs_list_add_request(req, dst); 409 res++; 410 if (res == INT_MAX) 411 goto out; 412 } 413 } 414 /* for latency reduction */ 415 cond_resched_lock(&nfsi->vfs_inode.i_lock); 416 } 417 out: 418 return res; 419 } 420 421 int __init nfs_init_nfspagecache(void) 422 { 423 nfs_page_cachep = kmem_cache_create("nfs_page", 424 sizeof(struct nfs_page), 425 0, SLAB_HWCACHE_ALIGN, 426 NULL); 427 if (nfs_page_cachep == NULL) 428 return -ENOMEM; 429 430 return 0; 431 } 432 433 void nfs_destroy_nfspagecache(void) 434 { 435 kmem_cache_destroy(nfs_page_cachep); 436 } 437 438