fs/nfs/read.c

   1 /*
   2  * linux/fs/nfs/read.c
   3  *
   4  * Block I/O for NFS
   5  *
   6  * Partial copy of Linus' read cache modifications to fs/nfs/file.c
   7  * modified for async RPC by [email protected]
   8  */
   9
  10 #include <linux/time.h>
  11 #include <linux/kernel.h>
  12 #include <linux/errno.h>
  13 #include <linux/fcntl.h>
  14 #include <linux/stat.h>
  15 #include <linux/mm.h>
  16 #include <linux/slab.h>
  17 #include <linux/pagemap.h>
  18 #include <linux/sunrpc/clnt.h>
  19 #include <linux/nfs_fs.h>
  20 #include <linux/nfs_page.h>
  21 #include <linux/module.h>
  22
  23 #include "nfs4_fs.h"
  24 #include "internal.h"
  25 #include "iostat.h"
  26 #include "fscache.h"
  27
  28 #define NFSDBG_FACILITY         NFSDBG_PAGECACHE
  29
  30 static const struct nfs_pageio_ops nfs_pageio_read_ops;
  31 static const struct rpc_call_ops nfs_read_common_ops;
  32 static const struct nfs_pgio_completion_ops nfs_async_read_completion_ops;
  33
  34 static struct kmem_cache *nfs_rdata_cachep;
  35
  36 struct nfs_read_header *nfs_readhdr_alloc(void)
  37 {
  38         struct nfs_read_header *rhdr;
  39
  40         rhdr = kmem_cache_zalloc(nfs_rdata_cachep, GFP_KERNEL);
  41         if (rhdr) {
  42                 struct nfs_pgio_header *hdr = &rhdr->header;
  43
  44                 INIT_LIST_HEAD(&hdr->pages);
  45                 INIT_LIST_HEAD(&hdr->rpc_list);
  46                 spin_lock_init(&hdr->lock);
  47                 atomic_set(&hdr->refcnt, 0);
  48         }
  49         return rhdr;
  50 }
  51 EXPORT_SYMBOL_GPL(nfs_readhdr_alloc);
  52
  53 static struct nfs_read_data *nfs_readdata_alloc(struct nfs_pgio_header *hdr,
  54                                                 unsigned int pagecount)
  55 {
  56         struct nfs_read_data *data, *prealloc;
  57
  58         prealloc = &container_of(hdr, struct nfs_read_header, header)->rpc_data;
  59         if (prealloc->header == NULL)
  60                 data = prealloc;
  61         else
  62                 data = kzalloc(sizeof(*data), GFP_KERNEL);
  63         if (!data)
  64                 goto out;
  65
  66         if (nfs_pgarray_set(&data->pages, pagecount)) {
  67                 data->header = hdr;
  68                 atomic_inc(&hdr->refcnt);
  69         } else {
  70                 if (data != prealloc)
  71                         kfree(data);
  72                 data = NULL;
  73         }
  74 out:
  75         return data;
  76 }
  77
  78 void nfs_readhdr_free(struct nfs_pgio_header *hdr)
  79 {
  80         struct nfs_read_header *rhdr = container_of(hdr, struct nfs_read_header, header);
  81
  82         kmem_cache_free(nfs_rdata_cachep, rhdr);
  83 }
  84 EXPORT_SYMBOL_GPL(nfs_readhdr_free);
  85
  86 void nfs_readdata_release(struct nfs_read_data *rdata)
  87 {
  88         struct nfs_pgio_header *hdr = rdata->header;
  89         struct nfs_read_header *read_header = container_of(hdr, struct nfs_read_header, header);
  90
  91         put_nfs_open_context(rdata->args.context);
  92         if (rdata->pages.pagevec != rdata->pages.page_array)
  93                 kfree(rdata->pages.pagevec);
  94         if (rdata != &read_header->rpc_data)
  95                 kfree(rdata);
  96         else
  97                 rdata->header = NULL;
  98         if (atomic_dec_and_test(&hdr->refcnt))
  99                 hdr->completion_ops->completion(hdr);
 100 }
 101 EXPORT_SYMBOL_GPL(nfs_readdata_release);
 102
 103 static
 104 int nfs_return_empty_page(struct page *page)
 105 {
 106         zero_user(page, 0, PAGE_CACHE_SIZE);
 107         SetPageUptodate(page);
 108         unlock_page(page);
 109         return 0;
 110 }
 111
 112 void nfs_pageio_init_read(struct nfs_pageio_descriptor *pgio,
 113                               struct inode *inode,
 114                               const struct nfs_pgio_completion_ops *compl_ops)
 115 {
 116         nfs_pageio_init(pgio, inode, &nfs_pageio_read_ops, compl_ops,
 117                         NFS_SERVER(inode)->rsize, 0);
 118 }
 119 EXPORT_SYMBOL_GPL(nfs_pageio_init_read);
 120
 121 void nfs_pageio_reset_read_mds(struct nfs_pageio_descriptor *pgio)
 122 {
 123         pgio->pg_ops = &nfs_pageio_read_ops;
 124         pgio->pg_bsize = NFS_SERVER(pgio->pg_inode)->rsize;
 125 }
 126 EXPORT_SYMBOL_GPL(nfs_pageio_reset_read_mds);
 127
 128 int nfs_readpage_async(struct nfs_open_context *ctx, struct inode *inode,
 129                        struct page *page)
 130 {
 131         struct nfs_page *new;
 132         unsigned int len;
 133         struct nfs_pageio_descriptor pgio;
 134
 135         len = nfs_page_length(page);
 136         if (len == 0)
 137                 return nfs_return_empty_page(page);
 138         new = nfs_create_request(ctx, inode, page, 0, len);
 139         if (IS_ERR(new)) {
 140                 unlock_page(page);
 141                 return PTR_ERR(new);
 142         }
 143         if (len < PAGE_CACHE_SIZE)
 144                 zero_user_segment(page, len, PAGE_CACHE_SIZE);
 145
 146         NFS_PROTO(inode)->read_pageio_init(&pgio, inode, &nfs_async_read_completion_ops);
 147         nfs_pageio_add_request(&pgio, new);
 148         nfs_pageio_complete(&pgio);
 149         NFS_I(inode)->read_io += pgio.pg_bytes_written;
 150         return 0;
 151 }
 152
 153 static void nfs_readpage_release(struct nfs_page *req)
 154 {
 155         struct inode *d_inode = req->wb_context->dentry->d_inode;
 156
 157         if (PageUptodate(req->wb_page))
 158                 nfs_readpage_to_fscache(d_inode, req->wb_page, 0);
 159
 160         unlock_page(req->wb_page);
 161
 162         dprintk("NFS: read done (%s/%Ld %d@%Ld)\n",
 163                         req->wb_context->dentry->d_inode->i_sb->s_id,
 164                         (long long)NFS_FILEID(req->wb_context->dentry->d_inode),
 165                         req->wb_bytes,
 166                         (long long)req_offset(req));
 167         nfs_release_request(req);
 168 }
 169
 170 /* Note io was page aligned */
 171 static void nfs_read_completion(struct nfs_pgio_header *hdr)
 172 {
 173         unsigned long bytes = 0;
 174
 175         if (test_bit(NFS_IOHDR_REDO, &hdr->flags))
 176                 goto out;
 177         while (!list_empty(&hdr->pages)) {
 178                 struct nfs_page *req = nfs_list_entry(hdr->pages.next);
 179                 struct page *page = req->wb_page;
 180
 181                 if (test_bit(NFS_IOHDR_EOF, &hdr->flags)) {
 182                         if (bytes > hdr->good_bytes)
 183                                 zero_user(page, 0, PAGE_SIZE);
 184                         else if (hdr->good_bytes - bytes < PAGE_SIZE)
 185                                 zero_user_segment(page,
 186                                         hdr->good_bytes & ~PAGE_MASK,
 187                                         PAGE_SIZE);
 188                 }
 189                 bytes += req->wb_bytes;
 190                 if (test_bit(NFS_IOHDR_ERROR, &hdr->flags)) {
 191                         if (bytes <= hdr->good_bytes)
 192                                 SetPageUptodate(page);
 193                 } else
 194                         SetPageUptodate(page);
 195                 nfs_list_remove_request(req);
 196                 nfs_readpage_release(req);
 197         }
 198 out:
 199         hdr->release(hdr);
 200 }
 201
 202 int nfs_initiate_read(struct rpc_clnt *clnt,
 203                       struct nfs_read_data *data,
 204                       const struct rpc_call_ops *call_ops, int flags)
 205 {
 206         struct inode *inode = data->header->inode;
 207         int swap_flags = IS_SWAPFILE(inode) ? NFS_RPC_SWAPFLAGS : 0;
 208         struct rpc_task *task;
 209         struct rpc_message msg = {
 210                 .rpc_argp = &data->args,
 211                 .rpc_resp = &data->res,
 212                 .rpc_cred = data->header->cred,
 213         };
 214         struct rpc_task_setup task_setup_data = {
 215                 .task = &data->task,
 216                 .rpc_client = clnt,
 217                 .rpc_message = &msg,
 218                 .callback_ops = call_ops,
 219                 .callback_data = data,
 220                 .workqueue = nfsiod_workqueue,
 221                 .flags = RPC_TASK_ASYNC | swap_flags | flags,
 222         };
 223
 224         /* Set up the initial task struct. */
 225         NFS_PROTO(inode)->read_setup(data, &msg);
 226
 227         dprintk("NFS: %5u initiated read call (req %s/%lld, %u bytes @ "
 228                         "offset %llu)\n",
 229                         data->task.tk_pid,
 230                         inode->i_sb->s_id,
 231                         (long long)NFS_FILEID(inode),
 232                         data->args.count,
 233                         (unsigned long long)data->args.offset);
 234
 235         task = rpc_run_task(&task_setup_data);
 236         if (IS_ERR(task))
 237                 return PTR_ERR(task);
 238         rpc_put_task(task);
 239         return 0;
 240 }
 241 EXPORT_SYMBOL_GPL(nfs_initiate_read);
 242
 243 /*
 244  * Set up the NFS read request struct
 245  */
 246 static void nfs_read_rpcsetup(struct nfs_read_data *data,
 247                 unsigned int count, unsigned int offset)
 248 {
 249         struct nfs_page *req = data->header->req;
 250
 251         data->args.fh     = NFS_FH(data->header->inode);
 252         data->args.offset = req_offset(req) + offset;
 253         data->args.pgbase = req->wb_pgbase + offset;
 254         data->args.pages  = data->pages.pagevec;
 255         data->args.count  = count;
 256         data->args.context = get_nfs_open_context(req->wb_context);
 257         data->args.lock_context = req->wb_lock_context;
 258
 259         data->res.fattr   = &data->fattr;
 260         data->res.count   = count;
 261         data->res.eof     = 0;
 262         nfs_fattr_init(&data->fattr);
 263 }
 264
 265 static int nfs_do_read(struct nfs_read_data *data,
 266                 const struct rpc_call_ops *call_ops)
 267 {
 268         struct inode *inode = data->header->inode;
 269
 270         return nfs_initiate_read(NFS_CLIENT(inode), data, call_ops, 0);
 271 }
 272
 273 static int
 274 nfs_do_multiple_reads(struct list_head *head,
 275                 const struct rpc_call_ops *call_ops)
 276 {
 277         struct nfs_read_data *data;
 278         int ret = 0;
 279
 280         while (!list_empty(head)) {
 281                 int ret2;
 282
 283                 data = list_first_entry(head, struct nfs_read_data, list);
 284                 list_del_init(&data->list);
 285
 286                 ret2 = nfs_do_read(data, call_ops);
 287                 if (ret == 0)
 288                         ret = ret2;
 289         }
 290         return ret;
 291 }
 292
 293 static void
 294 nfs_async_read_error(struct list_head *head)
 295 {
 296         struct nfs_page *req;
 297
 298         while (!list_empty(head)) {
 299                 req = nfs_list_entry(head->next);
 300                 nfs_list_remove_request(req);
 301                 nfs_readpage_release(req);
 302         }
 303 }
 304
 305 static const struct nfs_pgio_completion_ops nfs_async_read_completion_ops = {
 306         .error_cleanup = nfs_async_read_error,
 307         .completion = nfs_read_completion,
 308 };
 309
 310 static void nfs_pagein_error(struct nfs_pageio_descriptor *desc,
 311                 struct nfs_pgio_header *hdr)
 312 {
 313         set_bit(NFS_IOHDR_REDO, &hdr->flags);
 314         while (!list_empty(&hdr->rpc_list)) {
 315                 struct nfs_read_data *data = list_first_entry(&hdr->rpc_list,
 316                                 struct nfs_read_data, list);
 317                 list_del(&data->list);
 318                 nfs_readdata_release(data);
 319         }
 320         desc->pg_completion_ops->error_cleanup(&desc->pg_list);
 321 }
 322
 323 /*
 324  * Generate multiple requests to fill a single page.
 325  *
 326  * We optimize to reduce the number of read operations on the wire.  If we
 327  * detect that we're reading a page, or an area of a page, that is past the
 328  * end of file, we do not generate NFS read operations but just clear the
 329  * parts of the page that would have come back zero from the server anyway.
 330  *
 331  * We rely on the cached value of i_size to make this determination; another
 332  * client can fill pages on the server past our cached end-of-file, but we
 333  * won't see the new data until our attribute cache is updated.  This is more
 334  * or less conventional NFS client behavior.
 335  */
 336 static int nfs_pagein_multi(struct nfs_pageio_descriptor *desc,
 337                             struct nfs_pgio_header *hdr)
 338 {
 339         struct nfs_page *req = hdr->req;
 340         struct page *page = req->wb_page;
 341         struct nfs_read_data *data;
 342         size_t rsize = desc->pg_bsize, nbytes;
 343         unsigned int offset;
 344
 345         offset = 0;
 346         nbytes = desc->pg_count;
 347         do {
 348                 size_t len = min(nbytes,rsize);
 349
 350                 data = nfs_readdata_alloc(hdr, 1);
 351                 if (!data) {
 352                         nfs_pagein_error(desc, hdr);
 353                         return -ENOMEM;
 354                 }
 355                 data->pages.pagevec[0] = page;
 356                 nfs_read_rpcsetup(data, len, offset);
 357                 list_add(&data->list, &hdr->rpc_list);
 358                 nbytes -= len;
 359                 offset += len;
 360         } while (nbytes != 0);
 361
 362         nfs_list_remove_request(req);
 363         nfs_list_add_request(req, &hdr->pages);
 364         desc->pg_rpc_callops = &nfs_read_common_ops;
 365         return 0;
 366 }
 367
 368 static int nfs_pagein_one(struct nfs_pageio_descriptor *desc,
 369                           struct nfs_pgio_header *hdr)
 370 {
 371         struct nfs_page         *req;
 372         struct page             **pages;
 373         struct nfs_read_data    *data;
 374         struct list_head *head = &desc->pg_list;
 375
 376         data = nfs_readdata_alloc(hdr, nfs_page_array_len(desc->pg_base,
 377                                                           desc->pg_count));
 378         if (!data) {
 379                 nfs_pagein_error(desc, hdr);
 380                 return -ENOMEM;
 381         }
 382
 383         pages = data->pages.pagevec;
 384         while (!list_empty(head)) {
 385                 req = nfs_list_entry(head->next);
 386                 nfs_list_remove_request(req);
 387                 nfs_list_add_request(req, &hdr->pages);
 388                 *pages++ = req->wb_page;
 389         }
 390
 391         nfs_read_rpcsetup(data, desc->pg_count, 0);
 392         list_add(&data->list, &hdr->rpc_list);
 393         desc->pg_rpc_callops = &nfs_read_common_ops;
 394         return 0;
 395 }
 396
 397 int nfs_generic_pagein(struct nfs_pageio_descriptor *desc,
 398                        struct nfs_pgio_header *hdr)
 399 {
 400         if (desc->pg_bsize < PAGE_CACHE_SIZE)
 401                 return nfs_pagein_multi(desc, hdr);
 402         return nfs_pagein_one(desc, hdr);
 403 }
 404 EXPORT_SYMBOL_GPL(nfs_generic_pagein);
 405
 406 static int nfs_generic_pg_readpages(struct nfs_pageio_descriptor *desc)
 407 {
 408         struct nfs_read_header *rhdr;
 409         struct nfs_pgio_header *hdr;
 410         int ret;
 411
 412         rhdr = nfs_readhdr_alloc();
 413         if (!rhdr) {
 414                 desc->pg_completion_ops->error_cleanup(&desc->pg_list);
 415                 return -ENOMEM;
 416         }
 417         hdr = &rhdr->header;
 418         nfs_pgheader_init(desc, hdr, nfs_readhdr_free);
 419         atomic_inc(&hdr->refcnt);
 420         ret = nfs_generic_pagein(desc, hdr);
 421         if (ret == 0)
 422                 ret = nfs_do_multiple_reads(&hdr->rpc_list,
 423                                             desc->pg_rpc_callops);
 424         if (atomic_dec_and_test(&hdr->refcnt))
 425                 hdr->completion_ops->completion(hdr);
 426         return ret;
 427 }
 428
 429 static const struct nfs_pageio_ops nfs_pageio_read_ops = {
 430         .pg_test = nfs_generic_pg_test,
 431         .pg_doio = nfs_generic_pg_readpages,
 432 };
 433
 434 /*
 435  * This is the callback from RPC telling us whether a reply was
 436  * received or some error occurred (timeout or socket shutdown).
 437  */
 438 int nfs_readpage_result(struct rpc_task *task, struct nfs_read_data *data)
 439 {
 440         struct inode *inode = data->header->inode;
 441         int status;
 442
 443         dprintk("NFS: %s: %5u, (status %d)\n", __func__, task->tk_pid,
 444                         task->tk_status);
 445
 446         status = NFS_PROTO(inode)->read_done(task, data);
 447         if (status != 0)
 448                 return status;
 449
 450         nfs_add_stats(inode, NFSIOS_SERVERREADBYTES, data->res.count);
 451
 452         if (task->tk_status == -ESTALE) {
 453                 set_bit(NFS_INO_STALE, &NFS_I(inode)->flags);
 454                 nfs_mark_for_revalidate(inode);
 455         }
 456         return 0;
 457 }
 458
 459 static void nfs_readpage_retry(struct rpc_task *task, struct nfs_read_data *data)
 460 {
 461         struct nfs_readargs *argp = &data->args;
 462         struct nfs_readres *resp = &data->res;
 463
 464         /* This is a short read! */
 465         nfs_inc_stats(data->header->inode, NFSIOS_SHORTREAD);
 466         /* Has the server at least made some progress? */
 467         if (resp->count == 0) {
 468                 nfs_set_pgio_error(data->header, -EIO, argp->offset);
 469                 return;
 470         }
 471         /* Yes, so retry the read at the end of the data */
 472         data->mds_offset += resp->count;
 473         argp->offset += resp->count;
 474         argp->pgbase += resp->count;
 475         argp->count -= resp->count;
 476         rpc_restart_call_prepare(task);
 477 }
 478
 479 static void nfs_readpage_result_common(struct rpc_task *task, void *calldata)
 480 {
 481         struct nfs_read_data *data = calldata;
 482         struct nfs_pgio_header *hdr = data->header;
 483
 484         /* Note the only returns of nfs_readpage_result are 0 and -EAGAIN */
 485         if (nfs_readpage_result(task, data) != 0)
 486                 return;
 487         if (task->tk_status < 0)
 488                 nfs_set_pgio_error(hdr, task->tk_status, data->args.offset);
 489         else if (data->res.eof) {
 490                 loff_t bound;
 491
 492                 bound = data->args.offset + data->res.count;
 493                 spin_lock(&hdr->lock);
 494                 if (bound < hdr->io_start + hdr->good_bytes) {
 495                         set_bit(NFS_IOHDR_EOF, &hdr->flags);
 496                         clear_bit(NFS_IOHDR_ERROR, &hdr->flags);
 497                         hdr->good_bytes = bound - hdr->io_start;
 498                 }
 499                 spin_unlock(&hdr->lock);
 500         } else if (data->res.count != data->args.count)
 501                 nfs_readpage_retry(task, data);
 502 }
 503
 504 static void nfs_readpage_release_common(void *calldata)
 505 {
 506         nfs_readdata_release(calldata);
 507 }
 508
 509 void nfs_read_prepare(struct rpc_task *task, void *calldata)
 510 {
 511         struct nfs_read_data *data = calldata;
 512         NFS_PROTO(data->header->inode)->read_rpc_prepare(task, data);
 513 }
 514
 515 static const struct rpc_call_ops nfs_read_common_ops = {
 516         .rpc_call_prepare = nfs_read_prepare,
 517         .rpc_call_done = nfs_readpage_result_common,
 518         .rpc_release = nfs_readpage_release_common,
 519 };
 520
 521 /*
 522  * Read a page over NFS.
 523  * We read the page synchronously in the following case:
 524  *  -   The error flag is set for this page. This happens only when a
 525  *      previous async read operation failed.
 526  */
 527 int nfs_readpage(struct file *file, struct page *page)
 528 {
 529         struct nfs_open_context *ctx;
 530         struct inode *inode = page_file_mapping(page)->host;
 531         int             error;
 532
 533         dprintk("NFS: nfs_readpage (%p %ld@%lu)\n",
 534                 page, PAGE_CACHE_SIZE, page_file_index(page));
 535         nfs_inc_stats(inode, NFSIOS_VFSREADPAGE);
 536         nfs_add_stats(inode, NFSIOS_READPAGES, 1);
 537
 538         /*
 539          * Try to flush any pending writes to the file..
 540          *
 541          * NOTE! Because we own the page lock, there cannot
 542          * be any new pending writes generated at this point
 543          * for this page (other pages can be written to).
 544          */
 545         error = nfs_wb_page(inode, page);
 546         if (error)
 547                 goto out_unlock;
 548         if (PageUptodate(page))
 549                 goto out_unlock;
 550
 551         error = -ESTALE;
 552         if (NFS_STALE(inode))
 553                 goto out_unlock;
 554
 555         if (file == NULL) {
 556                 error = -EBADF;
 557                 ctx = nfs_find_open_context(inode, NULL, FMODE_READ);
 558                 if (ctx == NULL)
 559                         goto out_unlock;
 560         } else
 561                 ctx = get_nfs_open_context(nfs_file_open_context(file));
 562
 563         if (!IS_SYNC(inode)) {
 564                 error = nfs_readpage_from_fscache(ctx, inode, page);
 565                 if (error == 0)
 566                         goto out;
 567         }
 568
 569         error = nfs_readpage_async(ctx, inode, page);
 570
 571 out:
 572         put_nfs_open_context(ctx);
 573         return error;
 574 out_unlock:
 575         unlock_page(page);
 576         return error;
 577 }
 578
 579 struct nfs_readdesc {
 580         struct nfs_pageio_descriptor *pgio;
 581         struct nfs_open_context *ctx;
 582 };
 583
 584 static int
 585 readpage_async_filler(void *data, struct page *page)
 586 {
 587         struct nfs_readdesc *desc = (struct nfs_readdesc *)data;
 588         struct inode *inode = page_file_mapping(page)->host;
 589         struct nfs_page *new;
 590         unsigned int len;
 591         int error;
 592
 593         len = nfs_page_length(page);
 594         if (len == 0)
 595                 return nfs_return_empty_page(page);
 596
 597         new = nfs_create_request(desc->ctx, inode, page, 0, len);
 598         if (IS_ERR(new))
 599                 goto out_error;
 600
 601         if (len < PAGE_CACHE_SIZE)
 602                 zero_user_segment(page, len, PAGE_CACHE_SIZE);
 603         if (!nfs_pageio_add_request(desc->pgio, new)) {
 604                 error = desc->pgio->pg_error;
 605                 goto out_unlock;
 606         }
 607         return 0;
 608 out_error:
 609         error = PTR_ERR(new);
 610 out_unlock:
 611         unlock_page(page);
 612         return error;
 613 }
 614
 615 int nfs_readpages(struct file *filp, struct address_space *mapping,
 616                 struct list_head *pages, unsigned nr_pages)
 617 {
 618         struct nfs_pageio_descriptor pgio;
 619         struct nfs_readdesc desc = {
 620                 .pgio = &pgio,
 621         };
 622         struct inode *inode = mapping->host;
 623         unsigned long npages;
 624         int ret = -ESTALE;
 625
 626         dprintk("NFS: nfs_readpages (%s/%Ld %d)\n",
 627                         inode->i_sb->s_id,
 628                         (long long)NFS_FILEID(inode),
 629                         nr_pages);
 630         nfs_inc_stats(inode, NFSIOS_VFSREADPAGES);
 631
 632         if (NFS_STALE(inode))
 633                 goto out;
 634
 635         if (filp == NULL) {
 636                 desc.ctx = nfs_find_open_context(inode, NULL, FMODE_READ);
 637                 if (desc.ctx == NULL)
 638                         return -EBADF;
 639         } else
 640                 desc.ctx = get_nfs_open_context(nfs_file_open_context(filp));
 641
 642         /* attempt to read as many of the pages as possible from the cache
 643          * - this returns -ENOBUFS immediately if the cookie is negative
 644          */
 645         ret = nfs_readpages_from_fscache(desc.ctx, inode, mapping,
 646                                          pages, &nr_pages);
 647         if (ret == 0)
 648                 goto read_complete; /* all pages were read */
 649
 650         NFS_PROTO(inode)->read_pageio_init(&pgio, inode, &nfs_async_read_completion_ops);
 651
 652         ret = read_cache_pages(mapping, pages, readpage_async_filler, &desc);
 653
 654         nfs_pageio_complete(&pgio);
 655         NFS_I(inode)->read_io += pgio.pg_bytes_written;
 656         npages = (pgio.pg_bytes_written + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 657         nfs_add_stats(inode, NFSIOS_READPAGES, npages);
 658 read_complete:
 659         put_nfs_open_context(desc.ctx);
 660 out:
 661         return ret;
 662 }
 663
 664 int __init nfs_init_readpagecache(void)
 665 {
 666         nfs_rdata_cachep = kmem_cache_create("nfs_read_data",
 667                                              sizeof(struct nfs_read_header),
 668                                              0, SLAB_HWCACHE_ALIGN,
 669                                              NULL);
 670         if (nfs_rdata_cachep == NULL)
 671                 return -ENOMEM;
 672
 673         return 0;
 674 }
 675
 676 void nfs_destroy_readpagecache(void)
 677 {
 678         kmem_cache_destroy(nfs_rdata_cachep);
 679 }