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 okir@monad.swb.de
   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 "pnfs.h"
  24
  25 #include "nfs4_fs.h"
  26 #include "internal.h"
  27 #include "iostat.h"
  28 #include "fscache.h"
  29
  30 #define NFSDBG_FACILITY         NFSDBG_PAGECACHE
  31
  32 static const struct nfs_pageio_ops nfs_pageio_read_ops;
  33 static const struct rpc_call_ops nfs_read_common_ops;
  34 static const struct nfs_pgio_completion_ops nfs_async_read_completion_ops;
  35
  36 static struct kmem_cache *nfs_rdata_cachep;
  37
  38 struct nfs_read_header *nfs_readhdr_alloc(void)
  39 {
  40         struct nfs_read_header *rhdr;
  41
  42         rhdr = kmem_cache_zalloc(nfs_rdata_cachep, GFP_KERNEL);
  43         if (rhdr) {
  44                 struct nfs_pgio_header *hdr = &rhdr->header;
  45
  46                 INIT_LIST_HEAD(&hdr->pages);
  47                 INIT_LIST_HEAD(&hdr->rpc_list);
  48                 spin_lock_init(&hdr->lock);
  49                 atomic_set(&hdr->refcnt, 0);
  50         }
  51         return rhdr;
  52 }
  53
  54 static struct nfs_read_data *nfs_readdata_alloc(struct nfs_pgio_header *hdr,
  55                                                 unsigned int pagecount)
  56 {
  57         struct nfs_read_data *data, *prealloc;
  58
  59         prealloc = &container_of(hdr, struct nfs_read_header, header)->rpc_data;
  60         if (prealloc->header == NULL)
  61                 data = prealloc;
  62         else
  63                 data = kzalloc(sizeof(*data), GFP_KERNEL);
  64         if (!data)
  65                 goto out;
  66
  67         if (nfs_pgarray_set(&data->pages, pagecount)) {
  68                 data->header = hdr;
  69                 atomic_inc(&hdr->refcnt);
  70         } else {
  71                 if (data != prealloc)
  72                         kfree(data);
  73                 data = NULL;
  74         }
  75 out:
  76         return data;
  77 }
  78
  79 void nfs_readhdr_free(struct nfs_pgio_header *hdr)
  80 {
  81         struct nfs_read_header *rhdr = container_of(hdr, struct nfs_read_header, header);
  82
  83         kmem_cache_free(nfs_rdata_cachep, rhdr);
  84 }
  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
 102 static
 103 int nfs_return_empty_page(struct page *page)
 104 {
 105         zero_user(page, 0, PAGE_CACHE_SIZE);
 106         SetPageUptodate(page);
 107         unlock_page(page);
 108         return 0;
 109 }
 110
 111 void nfs_pageio_init_read_mds(struct nfs_pageio_descriptor *pgio,
 112                               struct inode *inode,
 113                               const struct nfs_pgio_completion_ops *compl_ops)
 114 {
 115         nfs_pageio_init(pgio, inode, &nfs_pageio_read_ops, compl_ops,
 116                         NFS_SERVER(inode)->rsize, 0);
 117 }
 118
 119 void nfs_pageio_reset_read_mds(struct nfs_pageio_descriptor *pgio)
 120 {
 121         pgio->pg_ops = &nfs_pageio_read_ops;
 122         pgio->pg_bsize = NFS_SERVER(pgio->pg_inode)->rsize;
 123 }
 124 EXPORT_SYMBOL_GPL(nfs_pageio_reset_read_mds);
 125
 126 void nfs_pageio_init_read(struct nfs_pageio_descriptor *pgio,
 127                           struct inode *inode,
 128                           const struct nfs_pgio_completion_ops *compl_ops)
 129 {
 130         if (!pnfs_pageio_init_read(pgio, inode, compl_ops))
 131                 nfs_pageio_init_read_mds(pgio, inode, compl_ops);
 132 }
 133
 134 int nfs_readpage_async(struct nfs_open_context *ctx, struct inode *inode,
 135                        struct page *page)
 136 {
 137         struct nfs_page *new;
 138         unsigned int len;
 139         struct nfs_pageio_descriptor pgio;
 140
 141         len = nfs_page_length(page);
 142         if (len == 0)
 143                 return nfs_return_empty_page(page);
 144         new = nfs_create_request(ctx, inode, page, 0, len);
 145         if (IS_ERR(new)) {
 146                 unlock_page(page);
 147                 return PTR_ERR(new);
 148         }
 149         if (len < PAGE_CACHE_SIZE)
 150                 zero_user_segment(page, len, PAGE_CACHE_SIZE);
 151
 152         nfs_pageio_init_read(&pgio, inode, &nfs_async_read_completion_ops);
 153         nfs_pageio_add_request(&pgio, new);
 154         nfs_pageio_complete(&pgio);
 155         return 0;
 156 }
 157
 158 static void nfs_readpage_release(struct nfs_page *req)
 159 {
 160         struct inode *d_inode = req->wb_context->dentry->d_inode;
 161
 162         if (PageUptodate(req->wb_page))
 163                 nfs_readpage_to_fscache(d_inode, req->wb_page, 0);
 164
 165         unlock_page(req->wb_page);
 166
 167         dprintk("NFS: read done (%s/%Ld %d@%Ld)\n",
 168                         req->wb_context->dentry->d_inode->i_sb->s_id,
 169                         (long long)NFS_FILEID(req->wb_context->dentry->d_inode),
 170                         req->wb_bytes,
 171                         (long long)req_offset(req));
 172         nfs_release_request(req);
 173 }
 174
 175 /* Note io was page aligned */
 176 static void nfs_read_completion(struct nfs_pgio_header *hdr)
 177 {
 178         unsigned long bytes = 0;
 179
 180         if (test_bit(NFS_IOHDR_REDO, &hdr->flags))
 181                 goto out;
 182         while (!list_empty(&hdr->pages)) {
 183                 struct nfs_page *req = nfs_list_entry(hdr->pages.next);
 184                 struct page *page = req->wb_page;
 185
 186                 if (test_bit(NFS_IOHDR_EOF, &hdr->flags)) {
 187                         if (bytes > hdr->good_bytes)
 188                                 zero_user(page, 0, PAGE_SIZE);
 189                         else if (hdr->good_bytes - bytes < PAGE_SIZE)
 190                                 zero_user_segment(page,
 191                                         hdr->good_bytes & ~PAGE_MASK,
 192                                         PAGE_SIZE);
 193                 }
 194                 bytes += req->wb_bytes;
 195                 if (test_bit(NFS_IOHDR_ERROR, &hdr->flags)) {
 196                         if (bytes <= hdr->good_bytes)
 197                                 SetPageUptodate(page);
 198                 } else
 199                         SetPageUptodate(page);
 200                 nfs_list_remove_request(req);
 201                 nfs_readpage_release(req);
 202         }
 203 out:
 204         hdr->release(hdr);
 205 }
 206
 207 int nfs_initiate_read(struct rpc_clnt *clnt,
 208                       struct nfs_read_data *data,
 209                       const struct rpc_call_ops *call_ops, int flags)
 210 {
 211         struct inode *inode = data->header->inode;
 212         int swap_flags = IS_SWAPFILE(inode) ? NFS_RPC_SWAPFLAGS : 0;
 213         struct rpc_task *task;
 214         struct rpc_message msg = {
 215                 .rpc_argp = &data->args,
 216                 .rpc_resp = &data->res,
 217                 .rpc_cred = data->header->cred,
 218         };
 219         struct rpc_task_setup task_setup_data = {
 220                 .task = &data->task,
 221                 .rpc_client = clnt,
 222                 .rpc_message = &msg,
 223                 .callback_ops = call_ops,
 224                 .callback_data = data,
 225                 .workqueue = nfsiod_workqueue,
 226                 .flags = RPC_TASK_ASYNC | swap_flags | flags,
 227         };
 228
 229         /* Set up the initial task struct. */
 230         NFS_PROTO(inode)->read_setup(data, &msg);
 231
 232         dprintk("NFS: %5u initiated read call (req %s/%lld, %u bytes @ "
 233                         "offset %llu)\n",
 234                         data->task.tk_pid,
 235                         inode->i_sb->s_id,
 236                         (long long)NFS_FILEID(inode),
 237                         data->args.count,
 238                         (unsigned long long)data->args.offset);
 239
 240         task = rpc_run_task(&task_setup_data);
 241         if (IS_ERR(task))
 242                 return PTR_ERR(task);
 243         rpc_put_task(task);
 244         return 0;
 245 }
 246 EXPORT_SYMBOL_GPL(nfs_initiate_read);
 247
 248 /*
 249  * Set up the NFS read request struct
 250  */
 251 static void nfs_read_rpcsetup(struct nfs_read_data *data,
 252                 unsigned int count, unsigned int offset)
 253 {
 254         struct nfs_page *req = data->header->req;
 255
 256         data->args.fh     = NFS_FH(data->header->inode);
 257         data->args.offset = req_offset(req) + offset;
 258         data->args.pgbase = req->wb_pgbase + offset;
 259         data->args.pages  = data->pages.pagevec;
 260         data->args.count  = count;
 261         data->args.context = get_nfs_open_context(req->wb_context);
 262         data->args.lock_context = req->wb_lock_context;
 263
 264         data->res.fattr   = &data->fattr;
 265         data->res.count   = count;
 266         data->res.eof     = 0;
 267         nfs_fattr_init(&data->fattr);
 268 }
 269
 270 static int nfs_do_read(struct nfs_read_data *data,
 271                 const struct rpc_call_ops *call_ops)
 272 {
 273         struct inode *inode = data->header->inode;
 274
 275         return nfs_initiate_read(NFS_CLIENT(inode), data, call_ops, 0);
 276 }
 277
 278 static int
 279 nfs_do_multiple_reads(struct list_head *head,
 280                 const struct rpc_call_ops *call_ops)
 281 {
 282         struct nfs_read_data *data;
 283         int ret = 0;
 284
 285         while (!list_empty(head)) {
 286                 int ret2;
 287
 288                 data = list_first_entry(head, struct nfs_read_data, list);
 289                 list_del_init(&data->list);
 290
 291                 ret2 = nfs_do_read(data, call_ops);
 292                 if (ret == 0)
 293                         ret = ret2;
 294         }
 295         return ret;
 296 }
 297
 298 static void
 299 nfs_async_read_error(struct list_head *head)
 300 {
 301         struct nfs_page *req;
 302
 303         while (!list_empty(head)) {
 304                 req = nfs_list_entry(head->next);
 305                 nfs_list_remove_request(req);
 306                 nfs_readpage_release(req);
 307         }
 308 }
 309
 310 static const struct nfs_pgio_completion_ops nfs_async_read_completion_ops = {
 311         .error_cleanup = nfs_async_read_error,
 312         .completion = nfs_read_completion,
 313 };
 314
 315 static void nfs_pagein_error(struct nfs_pageio_descriptor *desc,
 316                 struct nfs_pgio_header *hdr)
 317 {
 318         set_bit(NFS_IOHDR_REDO, &hdr->flags);
 319         while (!list_empty(&hdr->rpc_list)) {
 320                 struct nfs_read_data *data = list_first_entry(&hdr->rpc_list,
 321                                 struct nfs_read_data, list);
 322                 list_del(&data->list);
 323                 nfs_readdata_release(data);
 324         }
 325         desc->pg_completion_ops->error_cleanup(&desc->pg_list);
 326 }
 327
 328 /*
 329  * Generate multiple requests to fill a single page.
 330  *
 331  * We optimize to reduce the number of read operations on the wire.  If we
 332  * detect that we're reading a page, or an area of a page, that is past the
 333  * end of file, we do not generate NFS read operations but just clear the
 334  * parts of the page that would have come back zero from the server anyway.
 335  *
 336  * We rely on the cached value of i_size to make this determination; another
 337  * client can fill pages on the server past our cached end-of-file, but we
 338  * won't see the new data until our attribute cache is updated.  This is more
 339  * or less conventional NFS client behavior.
 340  */
 341 static int nfs_pagein_multi(struct nfs_pageio_descriptor *desc,
 342                             struct nfs_pgio_header *hdr)
 343 {
 344         struct nfs_page *req = hdr->req;
 345         struct page *page = req->wb_page;
 346         struct nfs_read_data *data;
 347         size_t rsize = desc->pg_bsize, nbytes;
 348         unsigned int offset;
 349
 350         offset = 0;
 351         nbytes = desc->pg_count;
 352         do {
 353                 size_t len = min(nbytes,rsize);
 354
 355                 data = nfs_readdata_alloc(hdr, 1);
 356                 if (!data) {
 357                         nfs_pagein_error(desc, hdr);
 358                         return -ENOMEM;
 359                 }
 360                 data->pages.pagevec[0] = page;
 361                 nfs_read_rpcsetup(data, len, offset);
 362                 list_add(&data->list, &hdr->rpc_list);
 363                 nbytes -= len;
 364                 offset += len;
 365         } while (nbytes != 0);
 366
 367         nfs_list_remove_request(req);
 368         nfs_list_add_request(req, &hdr->pages);
 369         desc->pg_rpc_callops = &nfs_read_common_ops;
 370         return 0;
 371 }
 372
 373 static int nfs_pagein_one(struct nfs_pageio_descriptor *desc,
 374                           struct nfs_pgio_header *hdr)
 375 {
 376         struct nfs_page         *req;
 377         struct page             **pages;
 378         struct nfs_read_data    *data;
 379         struct list_head *head = &desc->pg_list;
 380
 381         data = nfs_readdata_alloc(hdr, nfs_page_array_len(desc->pg_base,
 382                                                           desc->pg_count));
 383         if (!data) {
 384                 nfs_pagein_error(desc, hdr);
 385                 return -ENOMEM;
 386         }
 387
 388         pages = data->pages.pagevec;
 389         while (!list_empty(head)) {
 390                 req = nfs_list_entry(head->next);
 391                 nfs_list_remove_request(req);
 392                 nfs_list_add_request(req, &hdr->pages);
 393                 *pages++ = req->wb_page;
 394         }
 395
 396         nfs_read_rpcsetup(data, desc->pg_count, 0);
 397         list_add(&data->list, &hdr->rpc_list);
 398         desc->pg_rpc_callops = &nfs_read_common_ops;
 399         return 0;
 400 }
 401
 402 int nfs_generic_pagein(struct nfs_pageio_descriptor *desc,
 403                        struct nfs_pgio_header *hdr)
 404 {
 405         if (desc->pg_bsize < PAGE_CACHE_SIZE)
 406                 return nfs_pagein_multi(desc, hdr);
 407         return nfs_pagein_one(desc, hdr);
 408 }
 409
 410 static int nfs_generic_pg_readpages(struct nfs_pageio_descriptor *desc)
 411 {
 412         struct nfs_read_header *rhdr;
 413         struct nfs_pgio_header *hdr;
 414         int ret;
 415
 416         rhdr = nfs_readhdr_alloc();
 417         if (!rhdr) {
 418                 desc->pg_completion_ops->error_cleanup(&desc->pg_list);
 419                 return -ENOMEM;
 420         }
 421         hdr = &rhdr->header;
 422         nfs_pgheader_init(desc, hdr, nfs_readhdr_free);
 423         atomic_inc(&hdr->refcnt);
 424         ret = nfs_generic_pagein(desc, hdr);
 425         if (ret == 0)
 426                 ret = nfs_do_multiple_reads(&hdr->rpc_list,
 427                                             desc->pg_rpc_callops);
 428         if (atomic_dec_and_test(&hdr->refcnt))
 429                 hdr->completion_ops->completion(hdr);
 430         return ret;
 431 }
 432
 433 static const struct nfs_pageio_ops nfs_pageio_read_ops = {
 434         .pg_test = nfs_generic_pg_test,
 435         .pg_doio = nfs_generic_pg_readpages,
 436 };
 437
 438 /*
 439  * This is the callback from RPC telling us whether a reply was
 440  * received or some error occurred (timeout or socket shutdown).
 441  */
 442 int nfs_readpage_result(struct rpc_task *task, struct nfs_read_data *data)
 443 {
 444         struct inode *inode = data->header->inode;
 445         int status;
 446
 447         dprintk("NFS: %s: %5u, (status %d)\n", __func__, task->tk_pid,
 448                         task->tk_status);
 449
 450         status = NFS_PROTO(inode)->read_done(task, data);
 451         if (status != 0)
 452                 return status;
 453
 454         nfs_add_stats(inode, NFSIOS_SERVERREADBYTES, data->res.count);
 455
 456         if (task->tk_status == -ESTALE) {
 457                 set_bit(NFS_INO_STALE, &NFS_I(inode)->flags);
 458                 nfs_mark_for_revalidate(inode);
 459         }
 460         return 0;
 461 }
 462
 463 static void nfs_readpage_retry(struct rpc_task *task, struct nfs_read_data *data)
 464 {
 465         struct nfs_readargs *argp = &data->args;
 466         struct nfs_readres *resp = &data->res;
 467
 468         /* This is a short read! */
 469         nfs_inc_stats(data->header->inode, NFSIOS_SHORTREAD);
 470         /* Has the server at least made some progress? */
 471         if (resp->count == 0) {
 472                 nfs_set_pgio_error(data->header, -EIO, argp->offset);
 473                 return;
 474         }
 475         /* Yes, so retry the read at the end of the data */
 476         data->mds_offset += resp->count;
 477         argp->offset += resp->count;
 478         argp->pgbase += resp->count;
 479         argp->count -= resp->count;
 480         rpc_restart_call_prepare(task);
 481 }
 482
 483 static void nfs_readpage_result_common(struct rpc_task *task, void *calldata)
 484 {
 485         struct nfs_read_data *data = calldata;
 486         struct nfs_pgio_header *hdr = data->header;
 487
 488         /* Note the only returns of nfs_readpage_result are 0 and -EAGAIN */
 489         if (nfs_readpage_result(task, data) != 0)
 490                 return;
 491         if (task->tk_status < 0)
 492                 nfs_set_pgio_error(hdr, task->tk_status, data->args.offset);
 493         else if (data->res.eof) {
 494                 loff_t bound;
 495
 496                 bound = data->args.offset + data->res.count;
 497                 spin_lock(&hdr->lock);
 498                 if (bound < hdr->io_start + hdr->good_bytes) {
 499                         set_bit(NFS_IOHDR_EOF, &hdr->flags);
 500                         clear_bit(NFS_IOHDR_ERROR, &hdr->flags);
 501                         hdr->good_bytes = bound - hdr->io_start;
 502                 }
 503                 spin_unlock(&hdr->lock);
 504         } else if (data->res.count != data->args.count)
 505                 nfs_readpage_retry(task, data);
 506 }
 507
 508 static void nfs_readpage_release_common(void *calldata)
 509 {
 510         nfs_readdata_release(calldata);
 511 }
 512
 513 void nfs_read_prepare(struct rpc_task *task, void *calldata)
 514 {
 515         struct nfs_read_data *data = calldata;
 516         NFS_PROTO(data->header->inode)->read_rpc_prepare(task, data);
 517 }
 518
 519 static const struct rpc_call_ops nfs_read_common_ops = {
 520         .rpc_call_prepare = nfs_read_prepare,
 521         .rpc_call_done = nfs_readpage_result_common,
 522         .rpc_release = nfs_readpage_release_common,
 523 };
 524
 525 /*
 526  * Read a page over NFS.
 527  * We read the page synchronously in the following case:
 528  *  -   The error flag is set for this page. This happens only when a
 529  *      previous async read operation failed.
 530  */
 531 int nfs_readpage(struct file *file, struct page *page)
 532 {
 533         struct nfs_open_context *ctx;
 534         struct inode *inode = page->mapping->host;
 535         int             error;
 536
 537         dprintk("NFS: nfs_readpage (%p %ld@%lu)\n",
 538                 page, PAGE_CACHE_SIZE, page->index);
 539         nfs_inc_stats(inode, NFSIOS_VFSREADPAGE);
 540         nfs_add_stats(inode, NFSIOS_READPAGES, 1);
 541
 542         /*
 543          * Try to flush any pending writes to the file..
 544          *
 545          * NOTE! Because we own the page lock, there cannot
 546          * be any new pending writes generated at this point
 547          * for this page (other pages can be written to).
 548          */
 549         error = nfs_wb_page(inode, page);
 550         if (error)
 551                 goto out_unlock;
 552         if (PageUptodate(page))
 553                 goto out_unlock;
 554
 555         error = -ESTALE;
 556         if (NFS_STALE(inode))
 557                 goto out_unlock;
 558
 559         if (file == NULL) {
 560                 error = -EBADF;
 561                 ctx = nfs_find_open_context(inode, NULL, FMODE_READ);
 562                 if (ctx == NULL)
 563                         goto out_unlock;
 564         } else
 565                 ctx = get_nfs_open_context(nfs_file_open_context(file));
 566
 567         if (!IS_SYNC(inode)) {
 568                 error = nfs_readpage_from_fscache(ctx, inode, page);
 569                 if (error == 0)
 570                         goto out;
 571         }
 572
 573         error = nfs_readpage_async(ctx, inode, page);
 574
 575 out:
 576         put_nfs_open_context(ctx);
 577         return error;
 578 out_unlock:
 579         unlock_page(page);
 580         return error;
 581 }
 582
 583 struct nfs_readdesc {
 584         struct nfs_pageio_descriptor *pgio;
 585         struct nfs_open_context *ctx;
 586 };
 587
 588 static int
 589 readpage_async_filler(void *data, struct page *page)
 590 {
 591         struct nfs_readdesc *desc = (struct nfs_readdesc *)data;
 592         struct inode *inode = page->mapping->host;
 593         struct nfs_page *new;
 594         unsigned int len;
 595         int error;
 596
 597         len = nfs_page_length(page);
 598         if (len == 0)
 599                 return nfs_return_empty_page(page);
 600
 601         new = nfs_create_request(desc->ctx, inode, page, 0, len);
 602         if (IS_ERR(new))
 603                 goto out_error;
 604
 605         if (len < PAGE_CACHE_SIZE)
 606                 zero_user_segment(page, len, PAGE_CACHE_SIZE);
 607         if (!nfs_pageio_add_request(desc->pgio, new)) {
 608                 error = desc->pgio->pg_error;
 609                 goto out_unlock;
 610         }
 611         return 0;
 612 out_error:
 613         error = PTR_ERR(new);
 614 out_unlock:
 615         unlock_page(page);
 616         return error;
 617 }
 618
 619 int nfs_readpages(struct file *filp, struct address_space *mapping,
 620                 struct list_head *pages, unsigned nr_pages)
 621 {
 622         struct nfs_pageio_descriptor pgio;
 623         struct nfs_readdesc desc = {
 624                 .pgio = &pgio,
 625         };
 626         struct inode *inode = mapping->host;
 627         unsigned long npages;
 628         int ret = -ESTALE;
 629
 630         dprintk("NFS: nfs_readpages (%s/%Ld %d)\n",
 631                         inode->i_sb->s_id,
 632                         (long long)NFS_FILEID(inode),
 633                         nr_pages);
 634         nfs_inc_stats(inode, NFSIOS_VFSREADPAGES);
 635
 636         if (NFS_STALE(inode))
 637                 goto out;
 638
 639         if (filp == NULL) {
 640                 desc.ctx = nfs_find_open_context(inode, NULL, FMODE_READ);
 641                 if (desc.ctx == NULL)
 642                         return -EBADF;
 643         } else
 644                 desc.ctx = get_nfs_open_context(nfs_file_open_context(filp));
 645
 646         /* attempt to read as many of the pages as possible from the cache
 647          * - this returns -ENOBUFS immediately if the cookie is negative
 648          */
 649         ret = nfs_readpages_from_fscache(desc.ctx, inode, mapping,
 650                                          pages, &nr_pages);
 651         if (ret == 0)
 652                 goto read_complete; /* all pages were read */
 653
 654         nfs_pageio_init_read(&pgio, inode, &nfs_async_read_completion_ops);
 655
 656         ret = read_cache_pages(mapping, pages, readpage_async_filler, &desc);
 657
 658         nfs_pageio_complete(&pgio);
 659         npages = (pgio.pg_bytes_written + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 660         nfs_add_stats(inode, NFSIOS_READPAGES, npages);
 661 read_complete:
 662         put_nfs_open_context(desc.ctx);
 663 out:
 664         return ret;
 665 }
 666
 667 int __init nfs_init_readpagecache(void)
 668 {
 669         nfs_rdata_cachep = kmem_cache_create("nfs_read_data",
 670                                              sizeof(struct nfs_read_header),
 671                                              0, SLAB_HWCACHE_ALIGN,
 672                                              NULL);
 673         if (nfs_rdata_cachep == NULL)
 674                 return -ENOMEM;
 675
 676         return 0;
 677 }
 678
 679 void nfs_destroy_readpagecache(void)
 680 {
 681         kmem_cache_destroy(nfs_rdata_cachep);
 682 }