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