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