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 "nfs4_fs.h"
  24 #include "internal.h"
  25 #include "iostat.h"
  26 #include "fscache.h"
  27 #include "pnfs.h"
  28
  29 #define NFSDBG_FACILITY         NFSDBG_PAGECACHE
  30
  31 static const struct nfs_pageio_ops nfs_pageio_read_ops;
  32 static const struct rpc_call_ops nfs_read_common_ops;
  33 static const struct nfs_pgio_completion_ops nfs_async_read_completion_ops;
  34
  35 static struct kmem_cache *nfs_rdata_cachep;
  36
  37 struct nfs_read_header *nfs_readhdr_alloc(void)
  38 {
  39         struct nfs_read_header *rhdr;
  40
  41         rhdr = kmem_cache_zalloc(nfs_rdata_cachep, GFP_KERNEL);
  42         if (rhdr) {
  43                 struct nfs_pgio_header *hdr = &rhdr->header;
  44
  45                 INIT_LIST_HEAD(&hdr->pages);
  46                 INIT_LIST_HEAD(&hdr->rpc_list);
  47                 spin_lock_init(&hdr->lock);
  48                 atomic_set(&hdr->refcnt, 0);
  49         }
  50         return rhdr;
  51 }
  52 EXPORT_SYMBOL_GPL(nfs_readhdr_alloc);
  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 EXPORT_SYMBOL_GPL(nfs_readhdr_free);
  86
  87 void nfs_readdata_release(struct nfs_read_data *rdata)
  88 {
  89         struct nfs_pgio_header *hdr = rdata->header;
  90         struct nfs_read_header *read_header = container_of(hdr, struct nfs_read_header, header);
  91
  92         put_nfs_open_context(rdata->args.context);
  93         if (rdata->pages.pagevec != rdata->pages.page_array)
  94                 kfree(rdata->pages.pagevec);
  95         if (rdata == &read_header->rpc_data) {
  96                 rdata->header = NULL;
  97                 rdata = NULL;
  98         }
  99         if (atomic_dec_and_test(&hdr->refcnt))
 100                 hdr->completion_ops->completion(hdr);
 101         /* Note: we only free the rpc_task after callbacks are done.
 102          * See the comment in rpc_free_task() for why
 103          */
 104         kfree(rdata);
 105 }
 106 EXPORT_SYMBOL_GPL(nfs_readdata_release);
 107
 108 static
 109 int nfs_return_empty_page(struct page *page)
 110 {
 111         zero_user(page, 0, PAGE_CACHE_SIZE);
 112         SetPageUptodate(page);
 113         unlock_page(page);
 114         return 0;
 115 }
 116
 117 void nfs_pageio_init_read(struct nfs_pageio_descriptor *pgio,
 118                               struct inode *inode, bool force_mds,
 119                               const struct nfs_pgio_completion_ops *compl_ops)
 120 {
 121         struct nfs_server *server = NFS_SERVER(inode);
 122         const struct nfs_pageio_ops *pg_ops = &nfs_pageio_read_ops;
 123
 124 #ifdef CONFIG_NFS_V4_1
 125         if (server->pnfs_curr_ld && !force_mds)
 126                 pg_ops = server->pnfs_curr_ld->pg_read_ops;
 127 #endif
 128         nfs_pageio_init(pgio, inode, pg_ops, compl_ops, server->rsize, 0);
 129 }
 130 EXPORT_SYMBOL_GPL(nfs_pageio_init_read);
 131
 132 void nfs_pageio_reset_read_mds(struct nfs_pageio_descriptor *pgio)
 133 {
 134         pgio->pg_ops = &nfs_pageio_read_ops;
 135         pgio->pg_bsize = NFS_SERVER(pgio->pg_inode)->rsize;
 136 }
 137 EXPORT_SYMBOL_GPL(nfs_pageio_reset_read_mds);
 138
 139 int nfs_readpage_async(struct nfs_open_context *ctx, struct inode *inode,
 140                        struct page *page)
 141 {
 142         struct nfs_page *new;
 143         unsigned int len;
 144         struct nfs_pageio_descriptor pgio;
 145
 146         len = nfs_page_length(page);
 147         if (len == 0)
 148                 return nfs_return_empty_page(page);
 149         new = nfs_create_request(ctx, inode, page, 0, len);
 150         if (IS_ERR(new)) {
 151                 unlock_page(page);
 152                 return PTR_ERR(new);
 153         }
 154         if (len < PAGE_CACHE_SIZE)
 155                 zero_user_segment(page, len, PAGE_CACHE_SIZE);
 156
 157         nfs_pageio_init_read(&pgio, inode, false,
 158                              &nfs_async_read_completion_ops);
 159         nfs_pageio_add_request(&pgio, new);
 160         nfs_pageio_complete(&pgio);
 161         NFS_I(inode)->read_io += pgio.pg_bytes_written;
 162         return 0;
 163 }
 164
 165 static void nfs_readpage_release(struct nfs_page *req)
 166 {
 167         struct inode *d_inode = req->wb_context->dentry->d_inode;
 168
 169         if (PageUptodate(req->wb_page))
 170                 nfs_readpage_to_fscache(d_inode, req->wb_page, 0);
 171
 172         unlock_page(req->wb_page);
 173
 174         dprintk("NFS: read done (%s/%Lu %d@%Ld)\n",
 175                         req->wb_context->dentry->d_inode->i_sb->s_id,
 176                         (unsigned long long)NFS_FILEID(req->wb_context->dentry->d_inode),
 177                         req->wb_bytes,
 178                         (long long)req_offset(req));
 179         nfs_release_request(req);
 180 }
 181
 182 /* Note io was page aligned */
 183 static void nfs_read_completion(struct nfs_pgio_header *hdr)
 184 {
 185         unsigned long bytes = 0;
 186
 187         if (test_bit(NFS_IOHDR_REDO, &hdr->flags))
 188                 goto out;
 189         while (!list_empty(&hdr->pages)) {
 190                 struct nfs_page *req = nfs_list_entry(hdr->pages.next);
 191                 struct page *page = req->wb_page;
 192
 193                 if (test_bit(NFS_IOHDR_EOF, &hdr->flags)) {
 194                         if (bytes > hdr->good_bytes)
 195                                 zero_user(page, 0, PAGE_SIZE);
 196                         else if (hdr->good_bytes - bytes < PAGE_SIZE)
 197                                 zero_user_segment(page,
 198                                         hdr->good_bytes & ~PAGE_MASK,
 199                                         PAGE_SIZE);
 200                 }
 201                 bytes += req->wb_bytes;
 202                 if (test_bit(NFS_IOHDR_ERROR, &hdr->flags)) {
 203                         if (bytes <= hdr->good_bytes)
 204                                 SetPageUptodate(page);
 205                 } else
 206                         SetPageUptodate(page);
 207                 nfs_list_remove_request(req);
 208                 nfs_readpage_release(req);
 209         }
 210 out:
 211         hdr->release(hdr);
 212 }
 213
 214 int nfs_initiate_read(struct rpc_clnt *clnt,
 215                       struct nfs_read_data *data,
 216                       const struct rpc_call_ops *call_ops, int flags)
 217 {
 218         struct inode *inode = data->header->inode;
 219         int swap_flags = IS_SWAPFILE(inode) ? NFS_RPC_SWAPFLAGS : 0;
 220         struct rpc_task *task;
 221         struct rpc_message msg = {
 222                 .rpc_argp = &data->args,
 223                 .rpc_resp = &data->res,
 224                 .rpc_cred = data->header->cred,
 225         };
 226         struct rpc_task_setup task_setup_data = {
 227                 .task = &data->task,
 228                 .rpc_client = clnt,
 229                 .rpc_message = &msg,
 230                 .callback_ops = call_ops,
 231                 .callback_data = data,
 232                 .workqueue = nfsiod_workqueue,
 233                 .flags = RPC_TASK_ASYNC | swap_flags | flags,
 234         };
 235
 236         /* Set up the initial task struct. */
 237         NFS_PROTO(inode)->read_setup(data, &msg);
 238
 239         dprintk("NFS: %5u initiated read call (req %s/%llu, %u bytes @ "
 240                         "offset %llu)\n",
 241                         data->task.tk_pid,
 242                         inode->i_sb->s_id,
 243                         (unsigned long long)NFS_FILEID(inode),
 244                         data->args.count,
 245                         (unsigned long long)data->args.offset);
 246
 247         task = rpc_run_task(&task_setup_data);
 248         if (IS_ERR(task))
 249                 return PTR_ERR(task);
 250         rpc_put_task(task);
 251         return 0;
 252 }
 253 EXPORT_SYMBOL_GPL(nfs_initiate_read);
 254
 255 /*
 256  * Set up the NFS read request struct
 257  */
 258 static void nfs_read_rpcsetup(struct nfs_read_data *data,
 259                 unsigned int count, unsigned int offset)
 260 {
 261         struct nfs_page *req = data->header->req;
 262
 263         data->args.fh     = NFS_FH(data->header->inode);
 264         data->args.offset = req_offset(req) + offset;
 265         data->args.pgbase = req->wb_pgbase + offset;
 266         data->args.pages  = data->pages.pagevec;
 267         data->args.count  = count;
 268         data->args.context = get_nfs_open_context(req->wb_context);
 269         data->args.lock_context = req->wb_lock_context;
 270
 271         data->res.fattr   = &data->fattr;
 272         data->res.count   = count;
 273         data->res.eof     = 0;
 274         nfs_fattr_init(&data->fattr);
 275 }
 276
 277 static int nfs_do_read(struct nfs_read_data *data,
 278                 const struct rpc_call_ops *call_ops)
 279 {
 280         struct inode *inode = data->header->inode;
 281
 282         return nfs_initiate_read(NFS_CLIENT(inode), data, call_ops, 0);
 283 }
 284
 285 static int
 286 nfs_do_multiple_reads(struct list_head *head,
 287                 const struct rpc_call_ops *call_ops)
 288 {
 289         struct nfs_read_data *data;
 290         int ret = 0;
 291
 292         while (!list_empty(head)) {
 293                 int ret2;
 294
 295                 data = list_first_entry(head, struct nfs_read_data, list);
 296                 list_del_init(&data->list);
 297
 298                 ret2 = nfs_do_read(data, call_ops);
 299                 if (ret == 0)
 300                         ret = ret2;
 301         }
 302         return ret;
 303 }
 304
 305 static void
 306 nfs_async_read_error(struct list_head *head)
 307 {
 308         struct nfs_page *req;
 309
 310         while (!list_empty(head)) {
 311                 req = nfs_list_entry(head->next);
 312                 nfs_list_remove_request(req);
 313                 nfs_readpage_release(req);
 314         }
 315 }
 316
 317 static const struct nfs_pgio_completion_ops nfs_async_read_completion_ops = {
 318         .error_cleanup = nfs_async_read_error,
 319         .completion = nfs_read_completion,
 320 };
 321
 322 static void nfs_pagein_error(struct nfs_pageio_descriptor *desc,
 323                 struct nfs_pgio_header *hdr)
 324 {
 325         set_bit(NFS_IOHDR_REDO, &hdr->flags);
 326         while (!list_empty(&hdr->rpc_list)) {
 327                 struct nfs_read_data *data = list_first_entry(&hdr->rpc_list,
 328                                 struct nfs_read_data, list);
 329                 list_del(&data->list);
 330                 nfs_readdata_release(data);
 331         }
 332         desc->pg_completion_ops->error_cleanup(&desc->pg_list);
 333 }
 334
 335 /*
 336  * Generate multiple requests to fill a single page.
 337  *
 338  * We optimize to reduce the number of read operations on the wire.  If we
 339  * detect that we're reading a page, or an area of a page, that is past the
 340  * end of file, we do not generate NFS read operations but just clear the
 341  * parts of the page that would have come back zero from the server anyway.
 342  *
 343  * We rely on the cached value of i_size to make this determination; another
 344  * client can fill pages on the server past our cached end-of-file, but we
 345  * won't see the new data until our attribute cache is updated.  This is more
 346  * or less conventional NFS client behavior.
 347  */
 348 static int nfs_pagein_multi(struct nfs_pageio_descriptor *desc,
 349                             struct nfs_pgio_header *hdr)
 350 {
 351         struct nfs_page *req = hdr->req;
 352         struct page *page = req->wb_page;
 353         struct nfs_read_data *data;
 354         size_t rsize = desc->pg_bsize, nbytes;
 355         unsigned int offset;
 356
 357         offset = 0;
 358         nbytes = desc->pg_count;
 359         do {
 360                 size_t len = min(nbytes,rsize);
 361
 362                 data = nfs_readdata_alloc(hdr, 1);
 363                 if (!data) {
 364                         nfs_pagein_error(desc, hdr);
 365                         return -ENOMEM;
 366                 }
 367                 data->pages.pagevec[0] = page;
 368                 nfs_read_rpcsetup(data, len, offset);
 369                 list_add(&data->list, &hdr->rpc_list);
 370                 nbytes -= len;
 371                 offset += len;
 372         } while (nbytes != 0);
 373
 374         nfs_list_remove_request(req);
 375         nfs_list_add_request(req, &hdr->pages);
 376         desc->pg_rpc_callops = &nfs_read_common_ops;
 377         return 0;
 378 }
 379
 380 static int nfs_pagein_one(struct nfs_pageio_descriptor *desc,
 381                           struct nfs_pgio_header *hdr)
 382 {
 383         struct nfs_page         *req;
 384         struct page             **pages;
 385         struct nfs_read_data    *data;
 386         struct list_head *head = &desc->pg_list;
 387
 388         data = nfs_readdata_alloc(hdr, nfs_page_array_len(desc->pg_base,
 389                                                           desc->pg_count));
 390         if (!data) {
 391                 nfs_pagein_error(desc, hdr);
 392                 return -ENOMEM;
 393         }
 394
 395         pages = data->pages.pagevec;
 396         while (!list_empty(head)) {
 397                 req = nfs_list_entry(head->next);
 398                 nfs_list_remove_request(req);
 399                 nfs_list_add_request(req, &hdr->pages);
 400                 *pages++ = req->wb_page;
 401         }
 402
 403         nfs_read_rpcsetup(data, desc->pg_count, 0);
 404         list_add(&data->list, &hdr->rpc_list);
 405         desc->pg_rpc_callops = &nfs_read_common_ops;
 406         return 0;
 407 }
 408
 409 int nfs_generic_pagein(struct nfs_pageio_descriptor *desc,
 410                        struct nfs_pgio_header *hdr)
 411 {
 412         if (desc->pg_bsize < PAGE_CACHE_SIZE)
 413                 return nfs_pagein_multi(desc, hdr);
 414         return nfs_pagein_one(desc, hdr);
 415 }
 416 EXPORT_SYMBOL_GPL(nfs_generic_pagein);
 417
 418 static int nfs_generic_pg_readpages(struct nfs_pageio_descriptor *desc)
 419 {
 420         struct nfs_read_header *rhdr;
 421         struct nfs_pgio_header *hdr;
 422         int ret;
 423
 424         rhdr = nfs_readhdr_alloc();
 425         if (!rhdr) {
 426                 desc->pg_completion_ops->error_cleanup(&desc->pg_list);
 427                 return -ENOMEM;
 428         }
 429         hdr = &rhdr->header;
 430         nfs_pgheader_init(desc, hdr, nfs_readhdr_free);
 431         atomic_inc(&hdr->refcnt);
 432         ret = nfs_generic_pagein(desc, hdr);
 433         if (ret == 0)
 434                 ret = nfs_do_multiple_reads(&hdr->rpc_list,
 435                                             desc->pg_rpc_callops);
 436         if (atomic_dec_and_test(&hdr->refcnt))
 437                 hdr->completion_ops->completion(hdr);
 438         return ret;
 439 }
 440
 441 static const struct nfs_pageio_ops nfs_pageio_read_ops = {
 442         .pg_test = nfs_generic_pg_test,
 443         .pg_doio = nfs_generic_pg_readpages,
 444 };
 445
 446 /*
 447  * This is the callback from RPC telling us whether a reply was
 448  * received or some error occurred (timeout or socket shutdown).
 449  */
 450 int nfs_readpage_result(struct rpc_task *task, struct nfs_read_data *data)
 451 {
 452         struct inode *inode = data->header->inode;
 453         int status;
 454
 455         dprintk("NFS: %s: %5u, (status %d)\n", __func__, task->tk_pid,
 456                         task->tk_status);
 457
 458         status = NFS_PROTO(inode)->read_done(task, data);
 459         if (status != 0)
 460                 return status;
 461
 462         nfs_add_stats(inode, NFSIOS_SERVERREADBYTES, data->res.count);
 463
 464         if (task->tk_status == -ESTALE) {
 465                 set_bit(NFS_INO_STALE, &NFS_I(inode)->flags);
 466                 nfs_mark_for_revalidate(inode);
 467         }
 468         return 0;
 469 }
 470
 471 static void nfs_readpage_retry(struct rpc_task *task, struct nfs_read_data *data)
 472 {
 473         struct nfs_readargs *argp = &data->args;
 474         struct nfs_readres *resp = &data->res;
 475
 476         /* This is a short read! */
 477         nfs_inc_stats(data->header->inode, NFSIOS_SHORTREAD);
 478         /* Has the server at least made some progress? */
 479         if (resp->count == 0) {
 480                 nfs_set_pgio_error(data->header, -EIO, argp->offset);
 481                 return;
 482         }
 483         /* Yes, so retry the read at the end of the data */
 484         data->mds_offset += resp->count;
 485         argp->offset += resp->count;
 486         argp->pgbase += resp->count;
 487         argp->count -= resp->count;
 488         rpc_restart_call_prepare(task);
 489 }
 490
 491 static void nfs_readpage_result_common(struct rpc_task *task, void *calldata)
 492 {
 493         struct nfs_read_data *data = calldata;
 494         struct nfs_pgio_header *hdr = data->header;
 495
 496         /* Note the only returns of nfs_readpage_result are 0 and -EAGAIN */
 497         if (nfs_readpage_result(task, data) != 0)
 498                 return;
 499         if (task->tk_status < 0)
 500                 nfs_set_pgio_error(hdr, task->tk_status, data->args.offset);
 501         else if (data->res.eof) {
 502                 loff_t bound;
 503
 504                 bound = data->args.offset + data->res.count;
 505                 spin_lock(&hdr->lock);
 506                 if (bound < hdr->io_start + hdr->good_bytes) {
 507                         set_bit(NFS_IOHDR_EOF, &hdr->flags);
 508                         clear_bit(NFS_IOHDR_ERROR, &hdr->flags);
 509                         hdr->good_bytes = bound - hdr->io_start;
 510                 }
 511                 spin_unlock(&hdr->lock);
 512         } else if (data->res.count != data->args.count)
 513                 nfs_readpage_retry(task, data);
 514 }
 515
 516 static void nfs_readpage_release_common(void *calldata)
 517 {
 518         nfs_readdata_release(calldata);
 519 }
 520
 521 void nfs_read_prepare(struct rpc_task *task, void *calldata)
 522 {
 523         struct nfs_read_data *data = calldata;
 524         int err;
 525         err = NFS_PROTO(data->header->inode)->read_rpc_prepare(task, data);
 526         if (err)
 527                 rpc_exit(task, err);
 528 }
 529
 530 static const struct rpc_call_ops nfs_read_common_ops = {
 531         .rpc_call_prepare = nfs_read_prepare,
 532         .rpc_call_done = nfs_readpage_result_common,
 533         .rpc_release = nfs_readpage_release_common,
 534 };
 535
 536 /*
 537  * Read a page over NFS.
 538  * We read the page synchronously in the following case:
 539  *  -   The error flag is set for this page. This happens only when a
 540  *      previous async read operation failed.
 541  */
 542 int nfs_readpage(struct file *file, struct page *page)
 543 {
 544         struct nfs_open_context *ctx;
 545         struct inode *inode = page_file_mapping(page)->host;
 546         int             error;
 547
 548         dprintk("NFS: nfs_readpage (%p %ld@%lu)\n",
 549                 page, PAGE_CACHE_SIZE, page_file_index(page));
 550         nfs_inc_stats(inode, NFSIOS_VFSREADPAGE);
 551         nfs_add_stats(inode, NFSIOS_READPAGES, 1);
 552
 553         /*
 554          * Try to flush any pending writes to the file..
 555          *
 556          * NOTE! Because we own the page lock, there cannot
 557          * be any new pending writes generated at this point
 558          * for this page (other pages can be written to).
 559          */
 560         error = nfs_wb_page(inode, page);
 561         if (error)
 562                 goto out_unlock;
 563         if (PageUptodate(page))
 564                 goto out_unlock;
 565
 566         error = -ESTALE;
 567         if (NFS_STALE(inode))
 568                 goto out_unlock;
 569
 570         if (file == NULL) {
 571                 error = -EBADF;
 572                 ctx = nfs_find_open_context(inode, NULL, FMODE_READ);
 573                 if (ctx == NULL)
 574                         goto out_unlock;
 575         } else
 576                 ctx = get_nfs_open_context(nfs_file_open_context(file));
 577
 578         if (!IS_SYNC(inode)) {
 579                 error = nfs_readpage_from_fscache(ctx, inode, page);
 580                 if (error == 0)
 581                         goto out;
 582         }
 583
 584         error = nfs_readpage_async(ctx, inode, page);
 585
 586 out:
 587         put_nfs_open_context(ctx);
 588         return error;
 589 out_unlock:
 590         unlock_page(page);
 591         return error;
 592 }
 593
 594 struct nfs_readdesc {
 595         struct nfs_pageio_descriptor *pgio;
 596         struct nfs_open_context *ctx;
 597 };
 598
 599 static int
 600 readpage_async_filler(void *data, struct page *page)
 601 {
 602         struct nfs_readdesc *desc = (struct nfs_readdesc *)data;
 603         struct inode *inode = page_file_mapping(page)->host;
 604         struct nfs_page *new;
 605         unsigned int len;
 606         int error;
 607
 608         len = nfs_page_length(page);
 609         if (len == 0)
 610                 return nfs_return_empty_page(page);
 611
 612         new = nfs_create_request(desc->ctx, inode, page, 0, len);
 613         if (IS_ERR(new))
 614                 goto out_error;
 615
 616         if (len < PAGE_CACHE_SIZE)
 617                 zero_user_segment(page, len, PAGE_CACHE_SIZE);
 618         if (!nfs_pageio_add_request(desc->pgio, new)) {
 619                 error = desc->pgio->pg_error;
 620                 goto out_unlock;
 621         }
 622         return 0;
 623 out_error:
 624         error = PTR_ERR(new);
 625 out_unlock:
 626         unlock_page(page);
 627         return error;
 628 }
 629
 630 int nfs_readpages(struct file *filp, struct address_space *mapping,
 631                 struct list_head *pages, unsigned nr_pages)
 632 {
 633         struct nfs_pageio_descriptor pgio;
 634         struct nfs_readdesc desc = {
 635                 .pgio = &pgio,
 636         };
 637         struct inode *inode = mapping->host;
 638         unsigned long npages;
 639         int ret = -ESTALE;
 640
 641         dprintk("NFS: nfs_readpages (%s/%Lu %d)\n",
 642                         inode->i_sb->s_id,
 643                         (unsigned long long)NFS_FILEID(inode),
 644                         nr_pages);
 645         nfs_inc_stats(inode, NFSIOS_VFSREADPAGES);
 646
 647         if (NFS_STALE(inode))
 648                 goto out;
 649
 650         if (filp == NULL) {
 651                 desc.ctx = nfs_find_open_context(inode, NULL, FMODE_READ);
 652                 if (desc.ctx == NULL)
 653                         return -EBADF;
 654         } else
 655                 desc.ctx = get_nfs_open_context(nfs_file_open_context(filp));
 656
 657         /* attempt to read as many of the pages as possible from the cache
 658          * - this returns -ENOBUFS immediately if the cookie is negative
 659          */
 660         ret = nfs_readpages_from_fscache(desc.ctx, inode, mapping,
 661                                          pages, &nr_pages);
 662         if (ret == 0)
 663                 goto read_complete; /* all pages were read */
 664
 665         nfs_pageio_init_read(&pgio, inode, false,
 666                              &nfs_async_read_completion_ops);
 667
 668         ret = read_cache_pages(mapping, pages, readpage_async_filler, &desc);
 669
 670         nfs_pageio_complete(&pgio);
 671         NFS_I(inode)->read_io += pgio.pg_bytes_written;
 672         npages = (pgio.pg_bytes_written + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 673         nfs_add_stats(inode, NFSIOS_READPAGES, npages);
 674 read_complete:
 675         put_nfs_open_context(desc.ctx);
 676 out:
 677         return ret;
 678 }
 679
 680 int __init nfs_init_readpagecache(void)
 681 {
 682         nfs_rdata_cachep = kmem_cache_create("nfs_read_data",
 683                                              sizeof(struct nfs_read_header),
 684                                              0, SLAB_HWCACHE_ALIGN,
 685                                              NULL);
 686         if (nfs_rdata_cachep == NULL)
 687                 return -ENOMEM;
 688
 689         return 0;
 690 }
 691
 692 void nfs_destroy_readpagecache(void)
 693 {
 694         kmem_cache_destroy(nfs_rdata_cachep);
 695 }