fs/nfs/pagelist.c

   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/sunrpc/clnt.h>
  15 #include <linux/nfs3.h>
  16 #include <linux/nfs4.h>
  17 #include <linux/nfs_page.h>
  18 #include <linux/nfs_fs.h>
  19 #include <linux/nfs_mount.h>
  20
  21 #define NFS_PARANOIA 1
  22
  23 static kmem_cache_t *nfs_page_cachep;
  24
  25 static inline struct nfs_page *
  26 nfs_page_alloc(void)
  27 {
  28         struct nfs_page *p;
  29         p = kmem_cache_alloc(nfs_page_cachep, SLAB_KERNEL);
  30         if (p) {
  31                 memset(p, 0, sizeof(*p));
  32                 INIT_LIST_HEAD(&p->wb_list);
  33         }
  34         return p;
  35 }
  36
  37 static inline void
  38 nfs_page_free(struct nfs_page *p)
  39 {
  40         kmem_cache_free(nfs_page_cachep, p);
  41 }
  42
  43 /**
  44  * nfs_create_request - Create an NFS read/write request.
  45  * @file: file descriptor to use
  46  * @inode: inode to which the request is attached
  47  * @page: page to write
  48  * @offset: starting offset within the page for the write
  49  * @count: number of bytes to read/write
  50  *
  51  * The page must be locked by the caller. This makes sure we never
  52  * create two different requests for the same page, and avoids
  53  * a possible deadlock when we reach the hard limit on the number
  54  * of dirty pages.
  55  * User should ensure it is safe to sleep in this function.
  56  */
  57 struct nfs_page *
  58 nfs_create_request(struct nfs_open_context *ctx, struct inode *inode,
  59                    struct page *page,
  60                    unsigned int offset, unsigned int count)
  61 {
  62         struct nfs_server *server = NFS_SERVER(inode);
  63         struct nfs_page         *req;
  64
  65         /* Deal with hard limits.  */
  66         for (;;) {
  67                 /* try to allocate the request struct */
  68                 req = nfs_page_alloc();
  69                 if (req != NULL)
  70                         break;
  71
  72                 /* Try to free up at least one request in order to stay
  73                  * below the hard limit
  74                  */
  75                 if (signalled() && (server->flags & NFS_MOUNT_INTR))
  76                         return ERR_PTR(-ERESTARTSYS);
  77                 yield();
  78         }
  79
  80         /* Initialize the request struct. Initially, we assume a
  81          * long write-back delay. This will be adjusted in
  82          * update_nfs_request below if the region is not locked. */
  83         req->wb_page    = page;
  84         atomic_set(&req->wb_complete, 0);
  85         req->wb_index   = page->index;
  86         page_cache_get(page);
  87         BUG_ON(PagePrivate(page));
  88         BUG_ON(!PageLocked(page));
  89         BUG_ON(page->mapping->host != inode);
  90         req->wb_offset  = offset;
  91         req->wb_pgbase  = offset;
  92         req->wb_bytes   = count;
  93         atomic_set(&req->wb_count, 1);
  94         req->wb_context = get_nfs_open_context(ctx);
  95
  96         return req;
  97 }
  98
  99 /**
 100  * nfs_unlock_request - Unlock request and wake up sleepers.
 101  * @req:
 102  */
 103 void nfs_unlock_request(struct nfs_page *req)
 104 {
 105         if (!NFS_WBACK_BUSY(req)) {
 106                 printk(KERN_ERR "NFS: Invalid unlock attempted\n");
 107                 BUG();
 108         }
 109         smp_mb__before_clear_bit();
 110         clear_bit(PG_BUSY, &req->wb_flags);
 111         smp_mb__after_clear_bit();
 112         wake_up_bit(&req->wb_flags, PG_BUSY);
 113         nfs_release_request(req);
 114 }
 115
 116 /**
 117  * nfs_set_page_writeback_locked - Lock a request for writeback
 118  * @req:
 119  */
 120 int nfs_set_page_writeback_locked(struct nfs_page *req)
 121 {
 122         struct nfs_inode *nfsi = NFS_I(req->wb_context->dentry->d_inode);
 123
 124         if (!nfs_lock_request(req))
 125                 return 0;
 126         radix_tree_tag_set(&nfsi->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_WRITEBACK);
 127         return 1;
 128 }
 129
 130 /**
 131  * nfs_clear_page_writeback - Unlock request and wake up sleepers
 132  */
 133 void nfs_clear_page_writeback(struct nfs_page *req)
 134 {
 135         struct nfs_inode *nfsi = NFS_I(req->wb_context->dentry->d_inode);
 136
 137         if (req->wb_page != NULL) {
 138                 spin_lock(&nfsi->req_lock);
 139                 radix_tree_tag_clear(&nfsi->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_WRITEBACK);
 140                 spin_unlock(&nfsi->req_lock);
 141         }
 142         nfs_unlock_request(req);
 143 }
 144
 145 /**
 146  * nfs_clear_request - Free up all resources allocated to the request
 147  * @req:
 148  *
 149  * Release page resources associated with a write request after it
 150  * has completed.
 151  */
 152 void nfs_clear_request(struct nfs_page *req)
 153 {
 154         struct page *page = req->wb_page;
 155         if (page != NULL) {
 156                 page_cache_release(page);
 157                 req->wb_page = NULL;
 158         }
 159 }
 160
 161
 162 /**
 163  * nfs_release_request - Release the count on an NFS read/write request
 164  * @req: request to release
 165  *
 166  * Note: Should never be called with the spinlock held!
 167  */
 168 void
 169 nfs_release_request(struct nfs_page *req)
 170 {
 171         if (!atomic_dec_and_test(&req->wb_count))
 172                 return;
 173
 174 #ifdef NFS_PARANOIA
 175         BUG_ON (!list_empty(&req->wb_list));
 176         BUG_ON (NFS_WBACK_BUSY(req));
 177 #endif
 178
 179         /* Release struct file or cached credential */
 180         nfs_clear_request(req);
 181         put_nfs_open_context(req->wb_context);
 182         nfs_page_free(req);
 183 }
 184
 185 static int nfs_wait_bit_interruptible(void *word)
 186 {
 187         int ret = 0;
 188
 189         if (signal_pending(current))
 190                 ret = -ERESTARTSYS;
 191         else
 192                 schedule();
 193         return ret;
 194 }
 195
 196 /**
 197  * nfs_wait_on_request - Wait for a request to complete.
 198  * @req: request to wait upon.
 199  *
 200  * Interruptible by signals only if mounted with intr flag.
 201  * The user is responsible for holding a count on the request.
 202  */
 203 int
 204 nfs_wait_on_request(struct nfs_page *req)
 205 {
 206         struct rpc_clnt *clnt = NFS_CLIENT(req->wb_context->dentry->d_inode);
 207         sigset_t oldmask;
 208         int ret = 0;
 209
 210         if (!test_bit(PG_BUSY, &req->wb_flags))
 211                 goto out;
 212         /*
 213          * Note: the call to rpc_clnt_sigmask() suffices to ensure that we
 214          *       are not interrupted if intr flag is not set
 215          */
 216         rpc_clnt_sigmask(clnt, &oldmask);
 217         ret = out_of_line_wait_on_bit(&req->wb_flags, PG_BUSY,
 218                         nfs_wait_bit_interruptible, TASK_INTERRUPTIBLE);
 219         rpc_clnt_sigunmask(clnt, &oldmask);
 220 out:
 221         return ret;
 222 }
 223
 224 /**
 225  * nfs_coalesce_requests - Split coalesced requests out from a list.
 226  * @head: source list
 227  * @dst: destination list
 228  * @nmax: maximum number of requests to coalesce
 229  *
 230  * Moves a maximum of 'nmax' elements from one list to another.
 231  * The elements are checked to ensure that they form a contiguous set
 232  * of pages, and that the RPC credentials are the same.
 233  */
 234 int
 235 nfs_coalesce_requests(struct list_head *head, struct list_head *dst,
 236                       unsigned int nmax)
 237 {
 238         struct nfs_page         *req = NULL;
 239         unsigned int            npages = 0;
 240
 241         while (!list_empty(head)) {
 242                 struct nfs_page *prev = req;
 243
 244                 req = nfs_list_entry(head->next);
 245                 if (prev) {
 246                         if (req->wb_context->cred != prev->wb_context->cred)
 247                                 break;
 248                         if (req->wb_context->lockowner != prev->wb_context->lockowner)
 249                                 break;
 250                         if (req->wb_context->state != prev->wb_context->state)
 251                                 break;
 252                         if (req->wb_index != (prev->wb_index + 1))
 253                                 break;
 254
 255                         if (req->wb_pgbase != 0)
 256                                 break;
 257                 }
 258                 nfs_list_remove_request(req);
 259                 nfs_list_add_request(req, dst);
 260                 npages++;
 261                 if (req->wb_pgbase + req->wb_bytes != PAGE_CACHE_SIZE)
 262                         break;
 263                 if (npages >= nmax)
 264                         break;
 265         }
 266         return npages;
 267 }
 268
 269 #define NFS_SCAN_MAXENTRIES 16
 270 /**
 271  * nfs_scan_lock_dirty - Scan the radix tree for dirty requests
 272  * @nfsi: NFS inode
 273  * @dst: Destination list
 274  * @idx_start: lower bound of page->index to scan
 275  * @npages: idx_start + npages sets the upper bound to scan.
 276  *
 277  * Moves elements from one of the inode request lists.
 278  * If the number of requests is set to 0, the entire address_space
 279  * starting at index idx_start, is scanned.
 280  * The requests are *not* checked to ensure that they form a contiguous set.
 281  * You must be holding the inode's req_lock when calling this function
 282  */
 283 int
 284 nfs_scan_lock_dirty(struct nfs_inode *nfsi, struct list_head *dst,
 285               unsigned long idx_start, unsigned int npages)
 286 {
 287         struct nfs_page *pgvec[NFS_SCAN_MAXENTRIES];
 288         struct nfs_page *req;
 289         unsigned long idx_end;
 290         int found, i;
 291         int res;
 292
 293         res = 0;
 294         if (npages == 0)
 295                 idx_end = ~0;
 296         else
 297                 idx_end = idx_start + npages - 1;
 298
 299         for (;;) {
 300                 found = radix_tree_gang_lookup_tag(&nfsi->nfs_page_tree,
 301                                 (void **)&pgvec[0], idx_start, NFS_SCAN_MAXENTRIES,
 302                                 NFS_PAGE_TAG_DIRTY);
 303                 if (found <= 0)
 304                         break;
 305                 for (i = 0; i < found; i++) {
 306                         req = pgvec[i];
 307                         if (req->wb_index > idx_end)
 308                                 goto out;
 309
 310                         idx_start = req->wb_index + 1;
 311
 312                         if (nfs_set_page_writeback_locked(req)) {
 313                                 radix_tree_tag_clear(&nfsi->nfs_page_tree,
 314                                                 req->wb_index, NFS_PAGE_TAG_DIRTY);
 315                                 nfs_list_remove_request(req);
 316                                 nfs_list_add_request(req, dst);
 317                                 dec_zone_page_state(req->wb_page, NR_FILE_DIRTY);
 318                                 res++;
 319                         }
 320                 }
 321         }
 322 out:
 323         return res;
 324 }
 325
 326 /**
 327  * nfs_scan_list - Scan a list for matching requests
 328  * @nfsi: NFS inode
 329  * @head: One of the NFS inode request lists
 330  * @dst: Destination list
 331  * @idx_start: lower bound of page->index to scan
 332  * @npages: idx_start + npages sets the upper bound to scan.
 333  *
 334  * Moves elements from one of the inode request lists.
 335  * If the number of requests is set to 0, the entire address_space
 336  * starting at index idx_start, is scanned.
 337  * The requests are *not* checked to ensure that they form a contiguous set.
 338  * You must be holding the inode's req_lock when calling this function
 339  */
 340 int nfs_scan_list(struct nfs_inode *nfsi, struct list_head *head,
 341                 struct list_head *dst, unsigned long idx_start,
 342                 unsigned int npages)
 343 {
 344         struct nfs_page *pgvec[NFS_SCAN_MAXENTRIES];
 345         struct nfs_page *req;
 346         unsigned long idx_end;
 347         int found, i;
 348         int res;
 349
 350         res = 0;
 351         if (npages == 0)
 352                 idx_end = ~0;
 353         else
 354                 idx_end = idx_start + npages - 1;
 355
 356         for (;;) {
 357                 found = radix_tree_gang_lookup(&nfsi->nfs_page_tree,
 358                                 (void **)&pgvec[0], idx_start,
 359                                 NFS_SCAN_MAXENTRIES);
 360                 if (found <= 0)
 361                         break;
 362                 for (i = 0; i < found; i++) {
 363                         req = pgvec[i];
 364                         if (req->wb_index > idx_end)
 365                                 goto out;
 366                         idx_start = req->wb_index + 1;
 367                         if (req->wb_list_head != head)
 368                                 continue;
 369                         if (nfs_set_page_writeback_locked(req)) {
 370                                 nfs_list_remove_request(req);
 371                                 nfs_list_add_request(req, dst);
 372                                 res++;
 373                         }
 374                 }
 375
 376         }
 377 out:
 378         return res;
 379 }
 380
 381 int __init nfs_init_nfspagecache(void)
 382 {
 383         nfs_page_cachep = kmem_cache_create("nfs_page",
 384                                             sizeof(struct nfs_page),
 385                                             0, SLAB_HWCACHE_ALIGN,
 386                                             NULL, NULL);
 387         if (nfs_page_cachep == NULL)
 388                 return -ENOMEM;
 389
 390         return 0;
 391 }
 392
 393 void nfs_destroy_nfspagecache(void)
 394 {
 395         kmem_cache_destroy(nfs_page_cachep);
 396 }
 397