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 #include <linux/writeback.h>
  21
  22 #define NFS_PARANOIA 1
  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, 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         BUG_ON(PagePrivate(page));
  89         BUG_ON(!PageLocked(page));
  90         BUG_ON(page->mapping->host != inode);
  91         req->wb_offset  = offset;
  92         req->wb_pgbase  = offset;
  93         req->wb_bytes   = count;
  94         atomic_set(&req->wb_count, 1);
  95         req->wb_context = get_nfs_open_context(ctx);
  96
  97         return req;
  98 }
  99
 100 /**
 101  * nfs_unlock_request - Unlock request and wake up sleepers.
 102  * @req:
 103  */
 104 void nfs_unlock_request(struct nfs_page *req)
 105 {
 106         if (!NFS_WBACK_BUSY(req)) {
 107                 printk(KERN_ERR "NFS: Invalid unlock attempted\n");
 108                 BUG();
 109         }
 110         smp_mb__before_clear_bit();
 111         clear_bit(PG_BUSY, &req->wb_flags);
 112         smp_mb__after_clear_bit();
 113         wake_up_bit(&req->wb_flags, PG_BUSY);
 114         nfs_release_request(req);
 115 }
 116
 117 /**
 118  * nfs_set_page_writeback_locked - Lock a request for writeback
 119  * @req:
 120  */
 121 int nfs_set_page_writeback_locked(struct nfs_page *req)
 122 {
 123         struct nfs_inode *nfsi = NFS_I(req->wb_context->dentry->d_inode);
 124
 125         if (!nfs_lock_request(req))
 126                 return 0;
 127         radix_tree_tag_set(&nfsi->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_WRITEBACK);
 128         return 1;
 129 }
 130
 131 /**
 132  * nfs_clear_page_writeback - Unlock request and wake up sleepers
 133  */
 134 void nfs_clear_page_writeback(struct nfs_page *req)
 135 {
 136         struct nfs_inode *nfsi = NFS_I(req->wb_context->dentry->d_inode);
 137
 138         if (req->wb_page != NULL) {
 139                 spin_lock(&nfsi->req_lock);
 140                 radix_tree_tag_clear(&nfsi->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_WRITEBACK);
 141                 spin_unlock(&nfsi->req_lock);
 142         }
 143         nfs_unlock_request(req);
 144 }
 145
 146 /**
 147  * nfs_clear_request - Free up all resources allocated to the request
 148  * @req:
 149  *
 150  * Release page resources associated with a write request after it
 151  * has completed.
 152  */
 153 void nfs_clear_request(struct nfs_page *req)
 154 {
 155         struct page *page = req->wb_page;
 156         if (page != NULL) {
 157                 page_cache_release(page);
 158                 req->wb_page = NULL;
 159         }
 160 }
 161
 162
 163 /**
 164  * nfs_release_request - Release the count on an NFS read/write request
 165  * @req: request to release
 166  *
 167  * Note: Should never be called with the spinlock held!
 168  */
 169 void
 170 nfs_release_request(struct nfs_page *req)
 171 {
 172         if (!atomic_dec_and_test(&req->wb_count))
 173                 return;
 174
 175 #ifdef NFS_PARANOIA
 176         BUG_ON (!list_empty(&req->wb_list));
 177         BUG_ON (NFS_WBACK_BUSY(req));
 178 #endif
 179
 180         /* Release struct file or cached credential */
 181         nfs_clear_request(req);
 182         put_nfs_open_context(req->wb_context);
 183         nfs_page_free(req);
 184 }
 185
 186 static int nfs_wait_bit_interruptible(void *word)
 187 {
 188         int ret = 0;
 189
 190         if (signal_pending(current))
 191                 ret = -ERESTARTSYS;
 192         else
 193                 schedule();
 194         return ret;
 195 }
 196
 197 /**
 198  * nfs_wait_on_request - Wait for a request to complete.
 199  * @req: request to wait upon.
 200  *
 201  * Interruptible by signals only if mounted with intr flag.
 202  * The user is responsible for holding a count on the request.
 203  */
 204 int
 205 nfs_wait_on_request(struct nfs_page *req)
 206 {
 207         struct rpc_clnt *clnt = NFS_CLIENT(req->wb_context->dentry->d_inode);
 208         sigset_t oldmask;
 209         int ret = 0;
 210
 211         if (!test_bit(PG_BUSY, &req->wb_flags))
 212                 goto out;
 213         /*
 214          * Note: the call to rpc_clnt_sigmask() suffices to ensure that we
 215          *       are not interrupted if intr flag is not set
 216          */
 217         rpc_clnt_sigmask(clnt, &oldmask);
 218         ret = out_of_line_wait_on_bit(&req->wb_flags, PG_BUSY,
 219                         nfs_wait_bit_interruptible, TASK_INTERRUPTIBLE);
 220         rpc_clnt_sigunmask(clnt, &oldmask);
 221 out:
 222         return ret;
 223 }
 224
 225 /**
 226  * nfs_coalesce_requests - Split coalesced requests out from a list.
 227  * @head: source list
 228  * @dst: destination list
 229  * @nmax: maximum number of requests to coalesce
 230  *
 231  * Moves a maximum of 'nmax' elements from one list to another.
 232  * The elements are checked to ensure that they form a contiguous set
 233  * of pages, and that the RPC credentials are the same.
 234  */
 235 int
 236 nfs_coalesce_requests(struct list_head *head, struct list_head *dst,
 237                       unsigned int nmax)
 238 {
 239         struct nfs_page         *req = NULL;
 240         unsigned int            npages = 0;
 241
 242         while (!list_empty(head)) {
 243                 struct nfs_page *prev = req;
 244
 245                 req = nfs_list_entry(head->next);
 246                 if (prev) {
 247                         if (req->wb_context->cred != prev->wb_context->cred)
 248                                 break;
 249                         if (req->wb_context->lockowner != prev->wb_context->lockowner)
 250                                 break;
 251                         if (req->wb_context->state != prev->wb_context->state)
 252                                 break;
 253                         if (req->wb_index != (prev->wb_index + 1))
 254                                 break;
 255
 256                         if (req->wb_pgbase != 0)
 257                                 break;
 258                 }
 259                 nfs_list_remove_request(req);
 260                 nfs_list_add_request(req, dst);
 261                 npages++;
 262                 if (req->wb_pgbase + req->wb_bytes != PAGE_CACHE_SIZE)
 263                         break;
 264                 if (npages >= nmax)
 265                         break;
 266         }
 267         return npages;
 268 }
 269
 270 #define NFS_SCAN_MAXENTRIES 16
 271 /**
 272  * nfs_scan_dirty - Scan the radix tree for dirty requests
 273  * @mapping: pointer to address space
 274  * @wbc: writeback_control structure
 275  * @dst: Destination list
 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 long nfs_scan_dirty(struct address_space *mapping,
 284                         struct writeback_control *wbc,
 285                         struct list_head *dst)
 286 {
 287         struct nfs_inode *nfsi = NFS_I(mapping->host);
 288         struct nfs_page *pgvec[NFS_SCAN_MAXENTRIES];
 289         struct nfs_page *req;
 290         pgoff_t idx_start, idx_end;
 291         long res = 0;
 292         int found, i;
 293
 294         if (nfsi->ndirty == 0)
 295                 return 0;
 296         if (wbc->range_cyclic) {
 297                 idx_start = 0;
 298                 idx_end = ULONG_MAX;
 299         } else if (wbc->range_end == 0) {
 300                 idx_start = wbc->range_start >> PAGE_CACHE_SHIFT;
 301                 idx_end = ULONG_MAX;
 302         } else {
 303                 idx_start = wbc->range_start >> PAGE_CACHE_SHIFT;
 304                 idx_end = wbc->range_end >> PAGE_CACHE_SHIFT;
 305         }
 306
 307         for (;;) {
 308                 unsigned int toscan = NFS_SCAN_MAXENTRIES;
 309
 310                 found = radix_tree_gang_lookup_tag(&nfsi->nfs_page_tree,
 311                                 (void **)&pgvec[0], idx_start, toscan,
 312                                 NFS_PAGE_TAG_DIRTY);
 313
 314                 /* Did we make progress? */
 315                 if (found <= 0)
 316                         break;
 317
 318                 for (i = 0; i < found; i++) {
 319                         req = pgvec[i];
 320                         if (!wbc->range_cyclic && req->wb_index > idx_end)
 321                                 goto out;
 322
 323                         /* Try to lock request and mark it for writeback */
 324                         if (!nfs_set_page_writeback_locked(req))
 325                                 goto next;
 326                         radix_tree_tag_clear(&nfsi->nfs_page_tree,
 327                                         req->wb_index, NFS_PAGE_TAG_DIRTY);
 328                         nfsi->ndirty--;
 329                         nfs_list_remove_request(req);
 330                         nfs_list_add_request(req, dst);
 331                         res++;
 332                         if (res == LONG_MAX)
 333                                 goto out;
 334 next:
 335                         idx_start = req->wb_index + 1;
 336                 }
 337         }
 338 out:
 339         WARN_ON ((nfsi->ndirty == 0) != list_empty(&nfsi->dirty));
 340         return res;
 341 }
 342
 343 /**
 344  * nfs_scan_list - Scan a list for matching requests
 345  * @nfsi: NFS inode
 346  * @head: One of the NFS inode request lists
 347  * @dst: Destination list
 348  * @idx_start: lower bound of page->index to scan
 349  * @npages: idx_start + npages sets the upper bound to scan.
 350  *
 351  * Moves elements from one of the inode request lists.
 352  * If the number of requests is set to 0, the entire address_space
 353  * starting at index idx_start, is scanned.
 354  * The requests are *not* checked to ensure that they form a contiguous set.
 355  * You must be holding the inode's req_lock when calling this function
 356  */
 357 int nfs_scan_list(struct nfs_inode *nfsi, struct list_head *head,
 358                 struct list_head *dst, unsigned long idx_start,
 359                 unsigned int npages)
 360 {
 361         struct nfs_page *pgvec[NFS_SCAN_MAXENTRIES];
 362         struct nfs_page *req;
 363         unsigned long idx_end;
 364         int found, i;
 365         int res;
 366
 367         res = 0;
 368         if (npages == 0)
 369                 idx_end = ~0;
 370         else
 371                 idx_end = idx_start + npages - 1;
 372
 373         for (;;) {
 374                 found = radix_tree_gang_lookup(&nfsi->nfs_page_tree,
 375                                 (void **)&pgvec[0], idx_start,
 376                                 NFS_SCAN_MAXENTRIES);
 377                 if (found <= 0)
 378                         break;
 379                 for (i = 0; i < found; i++) {
 380                         req = pgvec[i];
 381                         if (req->wb_index > idx_end)
 382                                 goto out;
 383                         idx_start = req->wb_index + 1;
 384                         if (req->wb_list_head != head)
 385                                 continue;
 386                         if (nfs_set_page_writeback_locked(req)) {
 387                                 nfs_list_remove_request(req);
 388                                 nfs_list_add_request(req, dst);
 389                                 res++;
 390                         }
 391                 }
 392
 393         }
 394 out:
 395         return res;
 396 }
 397
 398 int __init nfs_init_nfspagecache(void)
 399 {
 400         nfs_page_cachep = kmem_cache_create("nfs_page",
 401                                             sizeof(struct nfs_page),
 402                                             0, SLAB_HWCACHE_ALIGN,
 403                                             NULL, NULL);
 404         if (nfs_page_cachep == NULL)
 405                 return -ENOMEM;
 406
 407         return 0;
 408 }
 409
 410 void nfs_destroy_nfspagecache(void)
 411 {
 412         kmem_cache_destroy(nfs_page_cachep);
 413 }
 414