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/config.h> 13 #include <linux/slab.h> 14 #include <linux/file.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 #define NFS_PARANOIA 1 23 24 static kmem_cache_t *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, SLAB_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, and avoids 54 * a possible deadlock when we reach the hard limit on the number 55 * of dirty pages. 56 * User should ensure it is safe to sleep in this function. 57 */ 58 struct nfs_page * 59 nfs_create_request(struct nfs_open_context *ctx, struct inode *inode, 60 struct page *page, 61 unsigned int offset, unsigned int count) 62 { 63 struct nfs_server *server = NFS_SERVER(inode); 64 struct nfs_page *req; 65 66 /* Deal with hard limits. */ 67 for (;;) { 68 /* try to allocate the request struct */ 69 req = nfs_page_alloc(); 70 if (req != NULL) 71 break; 72 73 /* Try to free up at least one request in order to stay 74 * below the hard limit 75 */ 76 if (signalled() && (server->flags & NFS_MOUNT_INTR)) 77 return ERR_PTR(-ERESTARTSYS); 78 yield(); 79 } 80 81 /* Initialize the request struct. Initially, we assume a 82 * long write-back delay. This will be adjusted in 83 * update_nfs_request below if the region is not locked. */ 84 req->wb_page = page; 85 atomic_set(&req->wb_complete, 0); 86 req->wb_index = page->index; 87 page_cache_get(page); 88 req->wb_offset = offset; 89 req->wb_pgbase = offset; 90 req->wb_bytes = count; 91 atomic_set(&req->wb_count, 1); 92 req->wb_context = get_nfs_open_context(ctx); 93 94 return req; 95 } 96 97 /** 98 * nfs_unlock_request - Unlock request and wake up sleepers. 99 * @req: 100 */ 101 void nfs_unlock_request(struct nfs_page *req) 102 { 103 if (!NFS_WBACK_BUSY(req)) { 104 printk(KERN_ERR "NFS: Invalid unlock attempted\n"); 105 BUG(); 106 } 107 smp_mb__before_clear_bit(); 108 clear_bit(PG_BUSY, &req->wb_flags); 109 smp_mb__after_clear_bit(); 110 wake_up_all(&req->wb_context->waitq); 111 nfs_release_request(req); 112 } 113 114 /** 115 * nfs_clear_request - Free up all resources allocated to the request 116 * @req: 117 * 118 * Release page resources associated with a write request after it 119 * has completed. 120 */ 121 void nfs_clear_request(struct nfs_page *req) 122 { 123 if (req->wb_page) { 124 page_cache_release(req->wb_page); 125 req->wb_page = NULL; 126 } 127 } 128 129 130 /** 131 * nfs_release_request - Release the count on an NFS read/write request 132 * @req: request to release 133 * 134 * Note: Should never be called with the spinlock held! 135 */ 136 void 137 nfs_release_request(struct nfs_page *req) 138 { 139 if (!atomic_dec_and_test(&req->wb_count)) 140 return; 141 142 #ifdef NFS_PARANOIA 143 BUG_ON (!list_empty(&req->wb_list)); 144 BUG_ON (NFS_WBACK_BUSY(req)); 145 #endif 146 147 /* Release struct file or cached credential */ 148 nfs_clear_request(req); 149 put_nfs_open_context(req->wb_context); 150 nfs_page_free(req); 151 } 152 153 /** 154 * nfs_list_add_request - Insert a request into a sorted list 155 * @req: request 156 * @head: head of list into which to insert the request. 157 * 158 * Note that the wb_list is sorted by page index in order to facilitate 159 * coalescing of requests. 160 * We use an insertion sort that is optimized for the case of appended 161 * writes. 162 */ 163 void 164 nfs_list_add_request(struct nfs_page *req, struct list_head *head) 165 { 166 struct list_head *pos; 167 168 #ifdef NFS_PARANOIA 169 if (!list_empty(&req->wb_list)) { 170 printk(KERN_ERR "NFS: Add to list failed!\n"); 171 BUG(); 172 } 173 #endif 174 list_for_each_prev(pos, head) { 175 struct nfs_page *p = nfs_list_entry(pos); 176 if (p->wb_index < req->wb_index) 177 break; 178 } 179 list_add(&req->wb_list, pos); 180 req->wb_list_head = head; 181 } 182 183 /** 184 * nfs_wait_on_request - Wait for a request to complete. 185 * @req: request to wait upon. 186 * 187 * Interruptible by signals only if mounted with intr flag. 188 * The user is responsible for holding a count on the request. 189 */ 190 int 191 nfs_wait_on_request(struct nfs_page *req) 192 { 193 struct inode *inode = req->wb_context->dentry->d_inode; 194 struct rpc_clnt *clnt = NFS_CLIENT(inode); 195 196 if (!NFS_WBACK_BUSY(req)) 197 return 0; 198 return nfs_wait_event(clnt, req->wb_context->waitq, !NFS_WBACK_BUSY(req)); 199 } 200 201 /** 202 * nfs_coalesce_requests - Split coalesced requests out from a list. 203 * @head: source list 204 * @dst: destination list 205 * @nmax: maximum number of requests to coalesce 206 * 207 * Moves a maximum of 'nmax' elements from one list to another. 208 * The elements are checked to ensure that they form a contiguous set 209 * of pages, and that the RPC credentials are the same. 210 */ 211 int 212 nfs_coalesce_requests(struct list_head *head, struct list_head *dst, 213 unsigned int nmax) 214 { 215 struct nfs_page *req = NULL; 216 unsigned int npages = 0; 217 218 while (!list_empty(head)) { 219 struct nfs_page *prev = req; 220 221 req = nfs_list_entry(head->next); 222 if (prev) { 223 if (req->wb_context->cred != prev->wb_context->cred) 224 break; 225 if (req->wb_context->lockowner != prev->wb_context->lockowner) 226 break; 227 if (req->wb_context->state != prev->wb_context->state) 228 break; 229 if (req->wb_index != (prev->wb_index + 1)) 230 break; 231 232 if (req->wb_pgbase != 0) 233 break; 234 } 235 nfs_list_remove_request(req); 236 nfs_list_add_request(req, dst); 237 npages++; 238 if (req->wb_pgbase + req->wb_bytes != PAGE_CACHE_SIZE) 239 break; 240 if (npages >= nmax) 241 break; 242 } 243 return npages; 244 } 245 246 /** 247 * nfs_scan_list - Scan a list for matching requests 248 * @head: One of the NFS inode request lists 249 * @dst: Destination list 250 * @idx_start: lower bound of page->index to scan 251 * @npages: idx_start + npages sets the upper bound to scan. 252 * 253 * Moves elements from one of the inode request lists. 254 * If the number of requests is set to 0, the entire address_space 255 * starting at index idx_start, is scanned. 256 * The requests are *not* checked to ensure that they form a contiguous set. 257 * You must be holding the inode's req_lock when calling this function 258 */ 259 int 260 nfs_scan_list(struct list_head *head, struct list_head *dst, 261 unsigned long idx_start, unsigned int npages) 262 { 263 struct list_head *pos, *tmp; 264 struct nfs_page *req; 265 unsigned long idx_end; 266 int res; 267 268 res = 0; 269 if (npages == 0) 270 idx_end = ~0; 271 else 272 idx_end = idx_start + npages - 1; 273 274 list_for_each_safe(pos, tmp, head) { 275 276 req = nfs_list_entry(pos); 277 278 if (req->wb_index < idx_start) 279 continue; 280 if (req->wb_index > idx_end) 281 break; 282 283 if (!nfs_lock_request(req)) 284 continue; 285 nfs_list_remove_request(req); 286 nfs_list_add_request(req, dst); 287 res++; 288 } 289 return res; 290 } 291 292 int nfs_init_nfspagecache(void) 293 { 294 nfs_page_cachep = kmem_cache_create("nfs_page", 295 sizeof(struct nfs_page), 296 0, SLAB_HWCACHE_ALIGN, 297 NULL, NULL); 298 if (nfs_page_cachep == NULL) 299 return -ENOMEM; 300 301 return 0; 302 } 303 304 void nfs_destroy_nfspagecache(void) 305 { 306 if (kmem_cache_destroy(nfs_page_cachep)) 307 printk(KERN_INFO "nfs_page: not all structures were freed\n"); 308 } 309 310