kernel/fs/nfs/pagelist.c

   1 /*
   2  * linux/fs/nfs/pagelist.c
   3  *
   4  * A set of helper functions for managing NFS read and write requests.
   5  * The main purpose of these routines is to provide support for the
   6  * coalescing of several requests into a single RPC call.
   7  *
   8  * Copyright 2000, 2001 (c) Trond Myklebust <trond.myklebust@fys.uio.no>
   9  *
  10  */
  11
  12 #include <linux/slab.h>
  13 #include <linux/file.h>
  14 #include <linux/sched.h>
  15 #include <linux/sunrpc/clnt.h>
  16 #include <linux/nfs.h>
  17 #include <linux/nfs3.h>
  18 #include <linux/nfs4.h>
  19 #include <linux/nfs_page.h>
  20 #include <linux/nfs_fs.h>
  21 #include <linux/nfs_mount.h>
  22 #include <linux/export.h>
  23
  24 #include "internal.h"
  25 #include "pnfs.h"
  26
  27 #define NFSDBG_FACILITY         NFSDBG_PAGECACHE
  28
  29 static struct kmem_cache *nfs_page_cachep;
  30 static const struct rpc_call_ops nfs_pgio_common_ops;
  31
  32 static bool nfs_pgarray_set(struct nfs_page_array *p, unsigned int pagecount)
  33 {
  34         p->npages = pagecount;
  35         if (pagecount <= ARRAY_SIZE(p->page_array))
  36                 p->pagevec = p->page_array;
  37         else {
  38                 p->pagevec = kcalloc(pagecount, sizeof(struct page *), GFP_KERNEL);
  39                 if (!p->pagevec)
  40                         p->npages = 0;
  41         }
  42         return p->pagevec != NULL;
  43 }
  44
  45 struct nfs_pgio_mirror *
  46 nfs_pgio_current_mirror(struct nfs_pageio_descriptor *desc)
  47 {
  48         return nfs_pgio_has_mirroring(desc) ?
  49                 &desc->pg_mirrors[desc->pg_mirror_idx] :
  50                 &desc->pg_mirrors[0];
  51 }
  52 EXPORT_SYMBOL_GPL(nfs_pgio_current_mirror);
  53
  54 void nfs_pgheader_init(struct nfs_pageio_descriptor *desc,
  55                        struct nfs_pgio_header *hdr,
  56                        void (*release)(struct nfs_pgio_header *hdr))
  57 {
  58         struct nfs_pgio_mirror *mirror = nfs_pgio_current_mirror(desc);
  59
  60
  61         hdr->req = nfs_list_entry(mirror->pg_list.next);
  62         hdr->inode = desc->pg_inode;
  63         hdr->cred = hdr->req->wb_context->cred;
  64         hdr->io_start = req_offset(hdr->req);
  65         hdr->good_bytes = mirror->pg_count;
  66         hdr->dreq = desc->pg_dreq;
  67         hdr->layout_private = desc->pg_layout_private;
  68         hdr->release = release;
  69         hdr->completion_ops = desc->pg_completion_ops;
  70         if (hdr->completion_ops->init_hdr)
  71                 hdr->completion_ops->init_hdr(hdr);
  72
  73         hdr->pgio_mirror_idx = desc->pg_mirror_idx;
  74 }
  75 EXPORT_SYMBOL_GPL(nfs_pgheader_init);
  76
  77 void nfs_set_pgio_error(struct nfs_pgio_header *hdr, int error, loff_t pos)
  78 {
  79         spin_lock(&hdr->lock);
  80         if (pos < hdr->io_start + hdr->good_bytes) {
  81                 set_bit(NFS_IOHDR_ERROR, &hdr->flags);
  82                 clear_bit(NFS_IOHDR_EOF, &hdr->flags);
  83                 hdr->good_bytes = pos - hdr->io_start;
  84                 hdr->error = error;
  85         }
  86         spin_unlock(&hdr->lock);
  87 }
  88
  89 static inline struct nfs_page *
  90 nfs_page_alloc(void)
  91 {
  92         struct nfs_page *p = kmem_cache_zalloc(nfs_page_cachep, GFP_NOIO);
  93         if (p)
  94                 INIT_LIST_HEAD(&p->wb_list);
  95         return p;
  96 }
  97
  98 static inline void
  99 nfs_page_free(struct nfs_page *p)
 100 {
 101         kmem_cache_free(nfs_page_cachep, p);
 102 }
 103
 104 static void
 105 nfs_iocounter_inc(struct nfs_io_counter *c)
 106 {
 107         atomic_inc(&c->io_count);
 108 }
 109
 110 static void
 111 nfs_iocounter_dec(struct nfs_io_counter *c)
 112 {
 113         if (atomic_dec_and_test(&c->io_count)) {
 114                 clear_bit(NFS_IO_INPROGRESS, &c->flags);
 115                 smp_mb__after_atomic();
 116                 wake_up_bit(&c->flags, NFS_IO_INPROGRESS);
 117         }
 118 }
 119
 120 static int
 121 __nfs_iocounter_wait(struct nfs_io_counter *c)
 122 {
 123         wait_queue_head_t *wq = bit_waitqueue(&c->flags, NFS_IO_INPROGRESS);
 124         DEFINE_WAIT_BIT(q, &c->flags, NFS_IO_INPROGRESS);
 125         int ret = 0;
 126
 127         do {
 128                 prepare_to_wait(wq, &q.wait, TASK_KILLABLE);
 129                 set_bit(NFS_IO_INPROGRESS, &c->flags);
 130                 if (atomic_read(&c->io_count) == 0)
 131                         break;
 132                 ret = nfs_wait_bit_killable(&q.key);
 133         } while (atomic_read(&c->io_count) != 0 && !ret);
 134         finish_wait(wq, &q.wait);
 135         return ret;
 136 }
 137
 138 /**
 139  * nfs_iocounter_wait - wait for i/o to complete
 140  * @c: nfs_io_counter to use
 141  *
 142  * returns -ERESTARTSYS if interrupted by a fatal signal.
 143  * Otherwise returns 0 once the io_count hits 0.
 144  */
 145 int
 146 nfs_iocounter_wait(struct nfs_io_counter *c)
 147 {
 148         if (atomic_read(&c->io_count) == 0)
 149                 return 0;
 150         return __nfs_iocounter_wait(c);
 151 }
 152
 153 /*
 154  * nfs_page_group_lock - lock the head of the page group
 155  * @req - request in group that is to be locked
 156  * @nonblock - if true don't block waiting for lock
 157  *
 158  * this lock must be held if modifying the page group list
 159  *
 160  * return 0 on success, < 0 on error: -EDELAY if nonblocking or the
 161  * result from wait_on_bit_lock
 162  *
 163  * NOTE: calling with nonblock=false should always have set the
 164  *       lock bit (see fs/buffer.c and other uses of wait_on_bit_lock
 165  *       with TASK_UNINTERRUPTIBLE), so there is no need to check the result.
 166  */
 167 int
 168 nfs_page_group_lock(struct nfs_page *req, bool nonblock)
 169 {
 170         struct nfs_page *head = req->wb_head;
 171
 172         WARN_ON_ONCE(head != head->wb_head);
 173
 174         if (!test_and_set_bit(PG_HEADLOCK, &head->wb_flags))
 175                 return 0;
 176
 177         if (!nonblock)
 178                 return wait_on_bit_lock(&head->wb_flags, PG_HEADLOCK,
 179                                 TASK_UNINTERRUPTIBLE);
 180
 181         return -EAGAIN;
 182 }
 183
 184 /*
 185  * nfs_page_group_lock_wait - wait for the lock to clear, but don't grab it
 186  * @req - a request in the group
 187  *
 188  * This is a blocking call to wait for the group lock to be cleared.
 189  */
 190 void
 191 nfs_page_group_lock_wait(struct nfs_page *req)
 192 {
 193         struct nfs_page *head = req->wb_head;
 194
 195         WARN_ON_ONCE(head != head->wb_head);
 196
 197         wait_on_bit(&head->wb_flags, PG_HEADLOCK,
 198                 TASK_UNINTERRUPTIBLE);
 199 }
 200
 201 /*
 202  * nfs_page_group_unlock - unlock the head of the page group
 203  * @req - request in group that is to be unlocked
 204  */
 205 void
 206 nfs_page_group_unlock(struct nfs_page *req)
 207 {
 208         struct nfs_page *head = req->wb_head;
 209
 210         WARN_ON_ONCE(head != head->wb_head);
 211
 212         smp_mb__before_atomic();
 213         clear_bit(PG_HEADLOCK, &head->wb_flags);
 214         smp_mb__after_atomic();
 215         wake_up_bit(&head->wb_flags, PG_HEADLOCK);
 216 }
 217
 218 /*
 219  * nfs_page_group_sync_on_bit_locked
 220  *
 221  * must be called with page group lock held
 222  */
 223 static bool
 224 nfs_page_group_sync_on_bit_locked(struct nfs_page *req, unsigned int bit)
 225 {
 226         struct nfs_page *head = req->wb_head;
 227         struct nfs_page *tmp;
 228
 229         WARN_ON_ONCE(!test_bit(PG_HEADLOCK, &head->wb_flags));
 230         WARN_ON_ONCE(test_and_set_bit(bit, &req->wb_flags));
 231
 232         tmp = req->wb_this_page;
 233         while (tmp != req) {
 234                 if (!test_bit(bit, &tmp->wb_flags))
 235                         return false;
 236                 tmp = tmp->wb_this_page;
 237         }
 238
 239         /* true! reset all bits */
 240         tmp = req;
 241         do {
 242                 clear_bit(bit, &tmp->wb_flags);
 243                 tmp = tmp->wb_this_page;
 244         } while (tmp != req);
 245
 246         return true;
 247 }
 248
 249 /*
 250  * nfs_page_group_sync_on_bit - set bit on current request, but only
 251  *   return true if the bit is set for all requests in page group
 252  * @req - request in page group
 253  * @bit - PG_* bit that is used to sync page group
 254  */
 255 bool nfs_page_group_sync_on_bit(struct nfs_page *req, unsigned int bit)
 256 {
 257         bool ret;
 258
 259         nfs_page_group_lock(req, false);
 260         ret = nfs_page_group_sync_on_bit_locked(req, bit);
 261         nfs_page_group_unlock(req);
 262
 263         return ret;
 264 }
 265
 266 /*
 267  * nfs_page_group_init - Initialize the page group linkage for @req
 268  * @req - a new nfs request
 269  * @prev - the previous request in page group, or NULL if @req is the first
 270  *         or only request in the group (the head).
 271  */
 272 static inline void
 273 nfs_page_group_init(struct nfs_page *req, struct nfs_page *prev)
 274 {
 275         struct inode *inode;
 276         WARN_ON_ONCE(prev == req);
 277
 278         if (!prev) {
 279                 /* a head request */
 280                 req->wb_head = req;
 281                 req->wb_this_page = req;
 282         } else {
 283                 /* a subrequest */
 284                 WARN_ON_ONCE(prev->wb_this_page != prev->wb_head);
 285                 WARN_ON_ONCE(!test_bit(PG_HEADLOCK, &prev->wb_head->wb_flags));
 286                 req->wb_head = prev->wb_head;
 287                 req->wb_this_page = prev->wb_this_page;
 288                 prev->wb_this_page = req;
 289
 290                 /* All subrequests take a ref on the head request until
 291                  * nfs_page_group_destroy is called */
 292                 kref_get(&req->wb_head->wb_kref);
 293
 294                 /* grab extra ref and bump the request count if head request
 295                  * has extra ref from the write/commit path to handle handoff
 296                  * between write and commit lists. */
 297                 if (test_bit(PG_INODE_REF, &prev->wb_head->wb_flags)) {
 298                         inode = page_file_mapping(req->wb_page)->host;
 299                         set_bit(PG_INODE_REF, &req->wb_flags);
 300                         kref_get(&req->wb_kref);
 301                         spin_lock(&inode->i_lock);
 302                         NFS_I(inode)->nrequests++;
 303                         spin_unlock(&inode->i_lock);
 304                 }
 305         }
 306 }
 307
 308 /*
 309  * nfs_page_group_destroy - sync the destruction of page groups
 310  * @req - request that no longer needs the page group
 311  *
 312  * releases the page group reference from each member once all
 313  * members have called this function.
 314  */
 315 static void
 316 nfs_page_group_destroy(struct kref *kref)
 317 {
 318         struct nfs_page *req = container_of(kref, struct nfs_page, wb_kref);
 319         struct nfs_page *tmp, *next;
 320
 321         /* subrequests must release the ref on the head request */
 322         if (req->wb_head != req)
 323                 nfs_release_request(req->wb_head);
 324
 325         if (!nfs_page_group_sync_on_bit(req, PG_TEARDOWN))
 326                 return;
 327
 328         tmp = req;
 329         do {
 330                 next = tmp->wb_this_page;
 331                 /* unlink and free */
 332                 tmp->wb_this_page = tmp;
 333                 tmp->wb_head = tmp;
 334                 nfs_free_request(tmp);
 335                 tmp = next;
 336         } while (tmp != req);
 337 }
 338
 339 /**
 340  * nfs_create_request - Create an NFS read/write request.
 341  * @ctx: open context to use
 342  * @page: page to write
 343  * @last: last nfs request created for this page group or NULL if head
 344  * @offset: starting offset within the page for the write
 345  * @count: number of bytes to read/write
 346  *
 347  * The page must be locked by the caller. This makes sure we never
 348  * create two different requests for the same page.
 349  * User should ensure it is safe to sleep in this function.
 350  */
 351 struct nfs_page *
 352 nfs_create_request(struct nfs_open_context *ctx, struct page *page,
 353                    struct nfs_page *last, unsigned int offset,
 354                    unsigned int count)
 355 {
 356         struct nfs_page         *req;
 357         struct nfs_lock_context *l_ctx;
 358
 359         if (test_bit(NFS_CONTEXT_BAD, &ctx->flags))
 360                 return ERR_PTR(-EBADF);
 361         /* try to allocate the request struct */
 362         req = nfs_page_alloc();
 363         if (req == NULL)
 364                 return ERR_PTR(-ENOMEM);
 365
 366         /* get lock context early so we can deal with alloc failures */
 367         l_ctx = nfs_get_lock_context(ctx);
 368         if (IS_ERR(l_ctx)) {
 369                 nfs_page_free(req);
 370                 return ERR_CAST(l_ctx);
 371         }
 372         req->wb_lock_context = l_ctx;
 373         nfs_iocounter_inc(&l_ctx->io_count);
 374
 375         /* Initialize the request struct. Initially, we assume a
 376          * long write-back delay. This will be adjusted in
 377          * update_nfs_request below if the region is not locked. */
 378         req->wb_page    = page;
 379         req->wb_index   = page_file_index(page);
 380         page_cache_get(page);
 381         req->wb_offset  = offset;
 382         req->wb_pgbase  = offset;
 383         req->wb_bytes   = count;
 384         req->wb_context = get_nfs_open_context(ctx);
 385         kref_init(&req->wb_kref);
 386         nfs_page_group_init(req, last);
 387         return req;
 388 }
 389
 390 /**
 391  * nfs_unlock_request - Unlock request and wake up sleepers.
 392  * @req:
 393  */
 394 void nfs_unlock_request(struct nfs_page *req)
 395 {
 396         if (!NFS_WBACK_BUSY(req)) {
 397                 printk(KERN_ERR "NFS: Invalid unlock attempted\n");
 398                 BUG();
 399         }
 400         smp_mb__before_atomic();
 401         clear_bit(PG_BUSY, &req->wb_flags);
 402         smp_mb__after_atomic();
 403         wake_up_bit(&req->wb_flags, PG_BUSY);
 404 }
 405
 406 /**
 407  * nfs_unlock_and_release_request - Unlock request and release the nfs_page
 408  * @req:
 409  */
 410 void nfs_unlock_and_release_request(struct nfs_page *req)
 411 {
 412         nfs_unlock_request(req);
 413         nfs_release_request(req);
 414 }
 415
 416 /*
 417  * nfs_clear_request - Free up all resources allocated to the request
 418  * @req:
 419  *
 420  * Release page and open context resources associated with a read/write
 421  * request after it has completed.
 422  */
 423 static void nfs_clear_request(struct nfs_page *req)
 424 {
 425         struct page *page = req->wb_page;
 426         struct nfs_open_context *ctx = req->wb_context;
 427         struct nfs_lock_context *l_ctx = req->wb_lock_context;
 428
 429         if (page != NULL) {
 430                 page_cache_release(page);
 431                 req->wb_page = NULL;
 432         }
 433         if (l_ctx != NULL) {
 434                 nfs_iocounter_dec(&l_ctx->io_count);
 435                 nfs_put_lock_context(l_ctx);
 436                 req->wb_lock_context = NULL;
 437         }
 438         if (ctx != NULL) {
 439                 put_nfs_open_context(ctx);
 440                 req->wb_context = NULL;
 441         }
 442 }
 443
 444 /**
 445  * nfs_release_request - Release the count on an NFS read/write request
 446  * @req: request to release
 447  *
 448  * Note: Should never be called with the spinlock held!
 449  */
 450 void nfs_free_request(struct nfs_page *req)
 451 {
 452         WARN_ON_ONCE(req->wb_this_page != req);
 453
 454         /* extra debug: make sure no sync bits are still set */
 455         WARN_ON_ONCE(test_bit(PG_TEARDOWN, &req->wb_flags));
 456         WARN_ON_ONCE(test_bit(PG_UNLOCKPAGE, &req->wb_flags));
 457         WARN_ON_ONCE(test_bit(PG_UPTODATE, &req->wb_flags));
 458         WARN_ON_ONCE(test_bit(PG_WB_END, &req->wb_flags));
 459         WARN_ON_ONCE(test_bit(PG_REMOVE, &req->wb_flags));
 460
 461         /* Release struct file and open context */
 462         nfs_clear_request(req);
 463         nfs_page_free(req);
 464 }
 465
 466 void nfs_release_request(struct nfs_page *req)
 467 {
 468         kref_put(&req->wb_kref, nfs_page_group_destroy);
 469 }
 470
 471 /**
 472  * nfs_wait_on_request - Wait for a request to complete.
 473  * @req: request to wait upon.
 474  *
 475  * Interruptible by fatal signals only.
 476  * The user is responsible for holding a count on the request.
 477  */
 478 int
 479 nfs_wait_on_request(struct nfs_page *req)
 480 {
 481         return wait_on_bit_io(&req->wb_flags, PG_BUSY,
 482                               TASK_UNINTERRUPTIBLE);
 483 }
 484
 485 /*
 486  * nfs_generic_pg_test - determine if requests can be coalesced
 487  * @desc: pointer to descriptor
 488  * @prev: previous request in desc, or NULL
 489  * @req: this request
 490  *
 491  * Returns zero if @req can be coalesced into @desc, otherwise it returns
 492  * the size of the request.
 493  */
 494 size_t nfs_generic_pg_test(struct nfs_pageio_descriptor *desc,
 495                            struct nfs_page *prev, struct nfs_page *req)
 496 {
 497         struct nfs_pgio_mirror *mirror = nfs_pgio_current_mirror(desc);
 498
 499
 500         if (mirror->pg_count > mirror->pg_bsize) {
 501                 /* should never happen */
 502                 WARN_ON_ONCE(1);
 503                 return 0;
 504         }
 505
 506         /*
 507          * Limit the request size so that we can still allocate a page array
 508          * for it without upsetting the slab allocator.
 509          */
 510         if (((mirror->pg_count + req->wb_bytes) >> PAGE_SHIFT) *
 511                         sizeof(struct page) > PAGE_SIZE)
 512                 return 0;
 513
 514         return min(mirror->pg_bsize - mirror->pg_count, (size_t)req->wb_bytes);
 515 }
 516 EXPORT_SYMBOL_GPL(nfs_generic_pg_test);
 517
 518 struct nfs_pgio_header *nfs_pgio_header_alloc(const struct nfs_rw_ops *ops)
 519 {
 520         struct nfs_pgio_header *hdr = ops->rw_alloc_header();
 521
 522         if (hdr) {
 523                 INIT_LIST_HEAD(&hdr->pages);
 524                 spin_lock_init(&hdr->lock);
 525                 hdr->rw_ops = ops;
 526         }
 527         return hdr;
 528 }
 529 EXPORT_SYMBOL_GPL(nfs_pgio_header_alloc);
 530
 531 /*
 532  * nfs_pgio_header_free - Free a read or write header
 533  * @hdr: The header to free
 534  */
 535 void nfs_pgio_header_free(struct nfs_pgio_header *hdr)
 536 {
 537         hdr->rw_ops->rw_free_header(hdr);
 538 }
 539 EXPORT_SYMBOL_GPL(nfs_pgio_header_free);
 540
 541 /**
 542  * nfs_pgio_data_destroy - make @hdr suitable for reuse
 543  *
 544  * Frees memory and releases refs from nfs_generic_pgio, so that it may
 545  * be called again.
 546  *
 547  * @hdr: A header that has had nfs_generic_pgio called
 548  */
 549 void nfs_pgio_data_destroy(struct nfs_pgio_header *hdr)
 550 {
 551         if (hdr->args.context)
 552                 put_nfs_open_context(hdr->args.context);
 553         if (hdr->page_array.pagevec != hdr->page_array.page_array)
 554                 kfree(hdr->page_array.pagevec);
 555 }
 556 EXPORT_SYMBOL_GPL(nfs_pgio_data_destroy);
 557
 558 /**
 559  * nfs_pgio_rpcsetup - Set up arguments for a pageio call
 560  * @hdr: The pageio hdr
 561  * @count: Number of bytes to read
 562  * @offset: Initial offset
 563  * @how: How to commit data (writes only)
 564  * @cinfo: Commit information for the call (writes only)
 565  */
 566 static void nfs_pgio_rpcsetup(struct nfs_pgio_header *hdr,
 567                               unsigned int count, unsigned int offset,
 568                               int how, struct nfs_commit_info *cinfo)
 569 {
 570         struct nfs_page *req = hdr->req;
 571
 572         /* Set up the RPC argument and reply structs
 573          * NB: take care not to mess about with hdr->commit et al. */
 574
 575         hdr->args.fh     = NFS_FH(hdr->inode);
 576         hdr->args.offset = req_offset(req) + offset;
 577         /* pnfs_set_layoutcommit needs this */
 578         hdr->mds_offset = hdr->args.offset;
 579         hdr->args.pgbase = req->wb_pgbase + offset;
 580         hdr->args.pages  = hdr->page_array.pagevec;
 581         hdr->args.count  = count;
 582         hdr->args.context = get_nfs_open_context(req->wb_context);
 583         hdr->args.lock_context = req->wb_lock_context;
 584         hdr->args.stable  = NFS_UNSTABLE;
 585         switch (how & (FLUSH_STABLE | FLUSH_COND_STABLE)) {
 586         case 0:
 587                 break;
 588         case FLUSH_COND_STABLE:
 589                 if (nfs_reqs_to_commit(cinfo))
 590                         break;
 591         default:
 592                 hdr->args.stable = NFS_FILE_SYNC;
 593         }
 594
 595         hdr->res.fattr   = &hdr->fattr;
 596         hdr->res.count   = count;
 597         hdr->res.eof     = 0;
 598         hdr->res.verf    = &hdr->verf;
 599         nfs_fattr_init(&hdr->fattr);
 600 }
 601
 602 /**
 603  * nfs_pgio_prepare - Prepare pageio hdr to go over the wire
 604  * @task: The current task
 605  * @calldata: pageio header to prepare
 606  */
 607 static void nfs_pgio_prepare(struct rpc_task *task, void *calldata)
 608 {
 609         struct nfs_pgio_header *hdr = calldata;
 610         int err;
 611         err = NFS_PROTO(hdr->inode)->pgio_rpc_prepare(task, hdr);
 612         if (err)
 613                 rpc_exit(task, err);
 614 }
 615
 616 int nfs_initiate_pgio(struct rpc_clnt *clnt, struct nfs_pgio_header *hdr,
 617                       struct rpc_cred *cred, const struct nfs_rpc_ops *rpc_ops,
 618                       const struct rpc_call_ops *call_ops, int how, int flags)
 619 {
 620         struct rpc_task *task;
 621         struct rpc_message msg = {
 622                 .rpc_argp = &hdr->args,
 623                 .rpc_resp = &hdr->res,
 624                 .rpc_cred = cred,
 625         };
 626         struct rpc_task_setup task_setup_data = {
 627                 .rpc_client = clnt,
 628                 .task = &hdr->task,
 629                 .rpc_message = &msg,
 630                 .callback_ops = call_ops,
 631                 .callback_data = hdr,
 632                 .workqueue = nfsiod_workqueue,
 633                 .flags = RPC_TASK_ASYNC | flags,
 634         };
 635         int ret = 0;
 636
 637         hdr->rw_ops->rw_initiate(hdr, &msg, rpc_ops, &task_setup_data, how);
 638
 639         dprintk("NFS: %5u initiated pgio call "
 640                 "(req %s/%llu, %u bytes @ offset %llu)\n",
 641                 hdr->task.tk_pid,
 642                 hdr->inode->i_sb->s_id,
 643                 (unsigned long long)NFS_FILEID(hdr->inode),
 644                 hdr->args.count,
 645                 (unsigned long long)hdr->args.offset);
 646
 647         task = rpc_run_task(&task_setup_data);
 648         if (IS_ERR(task)) {
 649                 ret = PTR_ERR(task);
 650                 goto out;
 651         }
 652         if (how & FLUSH_SYNC) {
 653                 ret = rpc_wait_for_completion_task(task);
 654                 if (ret == 0)
 655                         ret = task->tk_status;
 656         }
 657         rpc_put_task(task);
 658 out:
 659         return ret;
 660 }
 661 EXPORT_SYMBOL_GPL(nfs_initiate_pgio);
 662
 663 /**
 664  * nfs_pgio_error - Clean up from a pageio error
 665  * @desc: IO descriptor
 666  * @hdr: pageio header
 667  */
 668 static int nfs_pgio_error(struct nfs_pageio_descriptor *desc,
 669                           struct nfs_pgio_header *hdr)
 670 {
 671         struct nfs_pgio_mirror *mirror;
 672         u32 midx;
 673
 674         set_bit(NFS_IOHDR_REDO, &hdr->flags);
 675         nfs_pgio_data_destroy(hdr);
 676         hdr->completion_ops->completion(hdr);
 677         /* TODO: Make sure it's right to clean up all mirrors here
 678          *       and not just hdr->pgio_mirror_idx */
 679         for (midx = 0; midx < desc->pg_mirror_count; midx++) {
 680                 mirror = &desc->pg_mirrors[midx];
 681                 desc->pg_completion_ops->error_cleanup(&mirror->pg_list);
 682         }
 683         return -ENOMEM;
 684 }
 685
 686 /**
 687  * nfs_pgio_release - Release pageio data
 688  * @calldata: The pageio header to release
 689  */
 690 static void nfs_pgio_release(void *calldata)
 691 {
 692         struct nfs_pgio_header *hdr = calldata;
 693         if (hdr->rw_ops->rw_release)
 694                 hdr->rw_ops->rw_release(hdr);
 695         nfs_pgio_data_destroy(hdr);
 696         hdr->completion_ops->completion(hdr);
 697 }
 698
 699 static void nfs_pageio_mirror_init(struct nfs_pgio_mirror *mirror,
 700                                    unsigned int bsize)
 701 {
 702         INIT_LIST_HEAD(&mirror->pg_list);
 703         mirror->pg_bytes_written = 0;
 704         mirror->pg_count = 0;
 705         mirror->pg_bsize = bsize;
 706         mirror->pg_base = 0;
 707         mirror->pg_recoalesce = 0;
 708 }
 709
 710 /**
 711  * nfs_pageio_init - initialise a page io descriptor
 712  * @desc: pointer to descriptor
 713  * @inode: pointer to inode
 714  * @doio: pointer to io function
 715  * @bsize: io block size
 716  * @io_flags: extra parameters for the io function
 717  */
 718 void nfs_pageio_init(struct nfs_pageio_descriptor *desc,
 719                      struct inode *inode,
 720                      const struct nfs_pageio_ops *pg_ops,
 721                      const struct nfs_pgio_completion_ops *compl_ops,
 722                      const struct nfs_rw_ops *rw_ops,
 723                      size_t bsize,
 724                      int io_flags)
 725 {
 726         struct nfs_pgio_mirror *new;
 727         int i;
 728
 729         desc->pg_moreio = 0;
 730         desc->pg_inode = inode;
 731         desc->pg_ops = pg_ops;
 732         desc->pg_completion_ops = compl_ops;
 733         desc->pg_rw_ops = rw_ops;
 734         desc->pg_ioflags = io_flags;
 735         desc->pg_error = 0;
 736         desc->pg_lseg = NULL;
 737         desc->pg_dreq = NULL;
 738         desc->pg_layout_private = NULL;
 739         desc->pg_bsize = bsize;
 740
 741         desc->pg_mirror_count = 1;
 742         desc->pg_mirror_idx = 0;
 743
 744         if (pg_ops->pg_get_mirror_count) {
 745                 /* until we have a request, we don't have an lseg and no
 746                  * idea how many mirrors there will be */
 747                 new = kcalloc(NFS_PAGEIO_DESCRIPTOR_MIRROR_MAX,
 748                               sizeof(struct nfs_pgio_mirror), GFP_KERNEL);
 749                 desc->pg_mirrors_dynamic = new;
 750                 desc->pg_mirrors = new;
 751
 752                 for (i = 0; i < NFS_PAGEIO_DESCRIPTOR_MIRROR_MAX; i++)
 753                         nfs_pageio_mirror_init(&desc->pg_mirrors[i], bsize);
 754         } else {
 755                 desc->pg_mirrors_dynamic = NULL;
 756                 desc->pg_mirrors = desc->pg_mirrors_static;
 757                 nfs_pageio_mirror_init(&desc->pg_mirrors[0], bsize);
 758         }
 759 }
 760 EXPORT_SYMBOL_GPL(nfs_pageio_init);
 761
 762 /**
 763  * nfs_pgio_result - Basic pageio error handling
 764  * @task: The task that ran
 765  * @calldata: Pageio header to check
 766  */
 767 static void nfs_pgio_result(struct rpc_task *task, void *calldata)
 768 {
 769         struct nfs_pgio_header *hdr = calldata;
 770         struct inode *inode = hdr->inode;
 771
 772         dprintk("NFS: %s: %5u, (status %d)\n", __func__,
 773                 task->tk_pid, task->tk_status);
 774
 775         if (hdr->rw_ops->rw_done(task, hdr, inode) != 0)
 776                 return;
 777         if (task->tk_status < 0)
 778                 nfs_set_pgio_error(hdr, task->tk_status, hdr->args.offset);
 779         else
 780                 hdr->rw_ops->rw_result(task, hdr);
 781 }
 782
 783 /*
 784  * Create an RPC task for the given read or write request and kick it.
 785  * The page must have been locked by the caller.
 786  *
 787  * It may happen that the page we're passed is not marked dirty.
 788  * This is the case if nfs_updatepage detects a conflicting request
 789  * that has been written but not committed.
 790  */
 791 int nfs_generic_pgio(struct nfs_pageio_descriptor *desc,
 792                      struct nfs_pgio_header *hdr)
 793 {
 794         struct nfs_pgio_mirror *mirror = nfs_pgio_current_mirror(desc);
 795
 796         struct nfs_page         *req;
 797         struct page             **pages,
 798                                 *last_page;
 799         struct list_head *head = &mirror->pg_list;
 800         struct nfs_commit_info cinfo;
 801         unsigned int pagecount, pageused;
 802
 803         pagecount = nfs_page_array_len(mirror->pg_base, mirror->pg_count);
 804         if (!nfs_pgarray_set(&hdr->page_array, pagecount))
 805                 return nfs_pgio_error(desc, hdr);
 806
 807         nfs_init_cinfo(&cinfo, desc->pg_inode, desc->pg_dreq);
 808         pages = hdr->page_array.pagevec;
 809         last_page = NULL;
 810         pageused = 0;
 811         while (!list_empty(head)) {
 812                 req = nfs_list_entry(head->next);
 813                 nfs_list_remove_request(req);
 814                 nfs_list_add_request(req, &hdr->pages);
 815
 816                 if (!last_page || last_page != req->wb_page) {
 817                         pageused++;
 818                         if (pageused > pagecount)
 819                                 break;
 820                         *pages++ = last_page = req->wb_page;
 821                 }
 822         }
 823         if (WARN_ON_ONCE(pageused != pagecount))
 824                 return nfs_pgio_error(desc, hdr);
 825
 826         if ((desc->pg_ioflags & FLUSH_COND_STABLE) &&
 827             (desc->pg_moreio || nfs_reqs_to_commit(&cinfo)))
 828                 desc->pg_ioflags &= ~FLUSH_COND_STABLE;
 829
 830         /* Set up the argument struct */
 831         nfs_pgio_rpcsetup(hdr, mirror->pg_count, 0, desc->pg_ioflags, &cinfo);
 832         desc->pg_rpc_callops = &nfs_pgio_common_ops;
 833         return 0;
 834 }
 835 EXPORT_SYMBOL_GPL(nfs_generic_pgio);
 836
 837 static int nfs_generic_pg_pgios(struct nfs_pageio_descriptor *desc)
 838 {
 839         struct nfs_pgio_mirror *mirror;
 840         struct nfs_pgio_header *hdr;
 841         int ret;
 842
 843         mirror = nfs_pgio_current_mirror(desc);
 844
 845         hdr = nfs_pgio_header_alloc(desc->pg_rw_ops);
 846         if (!hdr) {
 847                 /* TODO: make sure this is right with mirroring - or
 848                  *       should it back out all mirrors? */
 849                 desc->pg_completion_ops->error_cleanup(&mirror->pg_list);
 850                 return -ENOMEM;
 851         }
 852         nfs_pgheader_init(desc, hdr, nfs_pgio_header_free);
 853         ret = nfs_generic_pgio(desc, hdr);
 854         if (ret == 0)
 855                 ret = nfs_initiate_pgio(NFS_CLIENT(hdr->inode),
 856                                         hdr,
 857                                         hdr->cred,
 858                                         NFS_PROTO(hdr->inode),
 859                                         desc->pg_rpc_callops,
 860                                         desc->pg_ioflags, 0);
 861         return ret;
 862 }
 863
 864 /*
 865  * nfs_pageio_setup_mirroring - determine if mirroring is to be used
 866  *                              by calling the pg_get_mirror_count op
 867  */
 868 static int nfs_pageio_setup_mirroring(struct nfs_pageio_descriptor *pgio,
 869                                        struct nfs_page *req)
 870 {
 871         int mirror_count = 1;
 872
 873         if (!pgio->pg_ops->pg_get_mirror_count)
 874                 return 0;
 875
 876         mirror_count = pgio->pg_ops->pg_get_mirror_count(pgio, req);
 877
 878         if (!mirror_count || mirror_count > NFS_PAGEIO_DESCRIPTOR_MIRROR_MAX)
 879                 return -EINVAL;
 880
 881         if (WARN_ON_ONCE(!pgio->pg_mirrors_dynamic))
 882                 return -EINVAL;
 883
 884         pgio->pg_mirror_count = mirror_count;
 885
 886         return 0;
 887 }
 888
 889 /*
 890  * nfs_pageio_stop_mirroring - stop using mirroring (set mirror count to 1)
 891  */
 892 void nfs_pageio_stop_mirroring(struct nfs_pageio_descriptor *pgio)
 893 {
 894         pgio->pg_mirror_count = 1;
 895         pgio->pg_mirror_idx = 0;
 896 }
 897
 898 static void nfs_pageio_cleanup_mirroring(struct nfs_pageio_descriptor *pgio)
 899 {
 900         pgio->pg_mirror_count = 1;
 901         pgio->pg_mirror_idx = 0;
 902         pgio->pg_mirrors = pgio->pg_mirrors_static;
 903         kfree(pgio->pg_mirrors_dynamic);
 904         pgio->pg_mirrors_dynamic = NULL;
 905 }
 906
 907 static bool nfs_match_open_context(const struct nfs_open_context *ctx1,
 908                 const struct nfs_open_context *ctx2)
 909 {
 910         return ctx1->cred == ctx2->cred && ctx1->state == ctx2->state;
 911 }
 912
 913 static bool nfs_match_lock_context(const struct nfs_lock_context *l1,
 914                 const struct nfs_lock_context *l2)
 915 {
 916         return l1->lockowner.l_owner == l2->lockowner.l_owner
 917                 && l1->lockowner.l_pid == l2->lockowner.l_pid;
 918 }
 919
 920 /**
 921  * nfs_can_coalesce_requests - test two requests for compatibility
 922  * @prev: pointer to nfs_page
 923  * @req: pointer to nfs_page
 924  *
 925  * The nfs_page structures 'prev' and 'req' are compared to ensure that the
 926  * page data area they describe is contiguous, and that their RPC
 927  * credentials, NFSv4 open state, and lockowners are the same.
 928  *
 929  * Return 'true' if this is the case, else return 'false'.
 930  */
 931 static bool nfs_can_coalesce_requests(struct nfs_page *prev,
 932                                       struct nfs_page *req,
 933                                       struct nfs_pageio_descriptor *pgio)
 934 {
 935         size_t size;
 936         struct file_lock_context *flctx;
 937
 938         if (prev) {
 939                 if (!nfs_match_open_context(req->wb_context, prev->wb_context))
 940                         return false;
 941                 flctx = d_inode(req->wb_context->dentry)->i_flctx;
 942                 if (flctx != NULL &&
 943                     !(list_empty_careful(&flctx->flc_posix) &&
 944                       list_empty_careful(&flctx->flc_flock)) &&
 945                     !nfs_match_lock_context(req->wb_lock_context,
 946                                             prev->wb_lock_context))
 947                         return false;
 948                 if (req_offset(req) != req_offset(prev) + prev->wb_bytes)
 949                         return false;
 950                 if (req->wb_page == prev->wb_page) {
 951                         if (req->wb_pgbase != prev->wb_pgbase + prev->wb_bytes)
 952                                 return false;
 953                 } else {
 954                         if (req->wb_pgbase != 0 ||
 955                             prev->wb_pgbase + prev->wb_bytes != PAGE_CACHE_SIZE)
 956                                 return false;
 957                 }
 958         }
 959         size = pgio->pg_ops->pg_test(pgio, prev, req);
 960         WARN_ON_ONCE(size > req->wb_bytes);
 961         if (size && size < req->wb_bytes)
 962                 req->wb_bytes = size;
 963         return size > 0;
 964 }
 965
 966 /**
 967  * nfs_pageio_do_add_request - Attempt to coalesce a request into a page list.
 968  * @desc: destination io descriptor
 969  * @req: request
 970  *
 971  * Returns true if the request 'req' was successfully coalesced into the
 972  * existing list of pages 'desc'.
 973  */
 974 static int nfs_pageio_do_add_request(struct nfs_pageio_descriptor *desc,
 975                                      struct nfs_page *req)
 976 {
 977         struct nfs_pgio_mirror *mirror = nfs_pgio_current_mirror(desc);
 978
 979         struct nfs_page *prev = NULL;
 980
 981         if (mirror->pg_count != 0) {
 982                 prev = nfs_list_entry(mirror->pg_list.prev);
 983         } else {
 984                 if (desc->pg_ops->pg_init)
 985                         desc->pg_ops->pg_init(desc, req);
 986                 mirror->pg_base = req->wb_pgbase;
 987         }
 988         if (!nfs_can_coalesce_requests(prev, req, desc))
 989                 return 0;
 990         nfs_list_remove_request(req);
 991         nfs_list_add_request(req, &mirror->pg_list);
 992         mirror->pg_count += req->wb_bytes;
 993         return 1;
 994 }
 995
 996 /*
 997  * Helper for nfs_pageio_add_request and nfs_pageio_complete
 998  */
 999 static void nfs_pageio_doio(struct nfs_pageio_descriptor *desc)
1000 {
1001         struct nfs_pgio_mirror *mirror = nfs_pgio_current_mirror(desc);
1002
1003
1004         if (!list_empty(&mirror->pg_list)) {
1005                 int error = desc->pg_ops->pg_doio(desc);
1006                 if (error < 0)
1007                         desc->pg_error = error;
1008                 else
1009                         mirror->pg_bytes_written += mirror->pg_count;
1010         }
1011         if (list_empty(&mirror->pg_list)) {
1012                 mirror->pg_count = 0;
1013                 mirror->pg_base = 0;
1014         }
1015 }
1016
1017 /**
1018  * nfs_pageio_add_request - Attempt to coalesce a request into a page list.
1019  * @desc: destination io descriptor
1020  * @req: request
1021  *
1022  * This may split a request into subrequests which are all part of the
1023  * same page group.
1024  *
1025  * Returns true if the request 'req' was successfully coalesced into the
1026  * existing list of pages 'desc'.
1027  */
1028 static int __nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
1029                            struct nfs_page *req)
1030 {
1031         struct nfs_pgio_mirror *mirror = nfs_pgio_current_mirror(desc);
1032
1033         struct nfs_page *subreq;
1034         unsigned int bytes_left = 0;
1035         unsigned int offset, pgbase;
1036
1037         nfs_page_group_lock(req, false);
1038
1039         subreq = req;
1040         bytes_left = subreq->wb_bytes;
1041         offset = subreq->wb_offset;
1042         pgbase = subreq->wb_pgbase;
1043
1044         do {
1045                 if (!nfs_pageio_do_add_request(desc, subreq)) {
1046                         /* make sure pg_test call(s) did nothing */
1047                         WARN_ON_ONCE(subreq->wb_bytes != bytes_left);
1048                         WARN_ON_ONCE(subreq->wb_offset != offset);
1049                         WARN_ON_ONCE(subreq->wb_pgbase != pgbase);
1050
1051                         nfs_page_group_unlock(req);
1052                         desc->pg_moreio = 1;
1053                         nfs_pageio_doio(desc);
1054                         if (desc->pg_error < 0)
1055                                 return 0;
1056                         if (mirror->pg_recoalesce)
1057                                 return 0;
1058                         /* retry add_request for this subreq */
1059                         nfs_page_group_lock(req, false);
1060                         continue;
1061                 }
1062
1063                 /* check for buggy pg_test call(s) */
1064                 WARN_ON_ONCE(subreq->wb_bytes + subreq->wb_pgbase > PAGE_SIZE);
1065                 WARN_ON_ONCE(subreq->wb_bytes > bytes_left);
1066                 WARN_ON_ONCE(subreq->wb_bytes == 0);
1067
1068                 bytes_left -= subreq->wb_bytes;
1069                 offset += subreq->wb_bytes;
1070                 pgbase += subreq->wb_bytes;
1071
1072                 if (bytes_left) {
1073                         subreq = nfs_create_request(req->wb_context,
1074                                         req->wb_page,
1075                                         subreq, pgbase, bytes_left);
1076                         if (IS_ERR(subreq))
1077                                 goto err_ptr;
1078                         nfs_lock_request(subreq);
1079                         subreq->wb_offset  = offset;
1080                         subreq->wb_index = req->wb_index;
1081                 }
1082         } while (bytes_left > 0);
1083
1084         nfs_page_group_unlock(req);
1085         return 1;
1086 err_ptr:
1087         desc->pg_error = PTR_ERR(subreq);
1088         nfs_page_group_unlock(req);
1089         return 0;
1090 }
1091
1092 static int nfs_do_recoalesce(struct nfs_pageio_descriptor *desc)
1093 {
1094         struct nfs_pgio_mirror *mirror = nfs_pgio_current_mirror(desc);
1095         LIST_HEAD(head);
1096
1097         do {
1098                 list_splice_init(&mirror->pg_list, &head);
1099                 mirror->pg_bytes_written -= mirror->pg_count;
1100                 mirror->pg_count = 0;
1101                 mirror->pg_base = 0;
1102                 mirror->pg_recoalesce = 0;
1103
1104                 desc->pg_moreio = 0;
1105
1106                 while (!list_empty(&head)) {
1107                         struct nfs_page *req;
1108
1109                         req = list_first_entry(&head, struct nfs_page, wb_list);
1110                         nfs_list_remove_request(req);
1111                         if (__nfs_pageio_add_request(desc, req))
1112                                 continue;
1113                         if (desc->pg_error < 0) {
1114                                 list_splice_tail(&head, &mirror->pg_list);
1115                                 mirror->pg_recoalesce = 1;
1116                                 return 0;
1117                         }
1118                         break;
1119                 }
1120         } while (mirror->pg_recoalesce);
1121         return 1;
1122 }
1123
1124 static int nfs_pageio_add_request_mirror(struct nfs_pageio_descriptor *desc,
1125                 struct nfs_page *req)
1126 {
1127         int ret;
1128
1129         do {
1130                 ret = __nfs_pageio_add_request(desc, req);
1131                 if (ret)
1132                         break;
1133                 if (desc->pg_error < 0)
1134                         break;
1135                 ret = nfs_do_recoalesce(desc);
1136         } while (ret);
1137
1138         return ret;
1139 }
1140
1141 int nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
1142                            struct nfs_page *req)
1143 {
1144         u32 midx;
1145         unsigned int pgbase, offset, bytes;
1146         struct nfs_page *dupreq, *lastreq;
1147
1148         pgbase = req->wb_pgbase;
1149         offset = req->wb_offset;
1150         bytes = req->wb_bytes;
1151
1152         nfs_pageio_setup_mirroring(desc, req);
1153
1154         for (midx = 0; midx < desc->pg_mirror_count; midx++) {
1155                 if (midx) {
1156                         nfs_page_group_lock(req, false);
1157
1158                         /* find the last request */
1159                         for (lastreq = req->wb_head;
1160                              lastreq->wb_this_page != req->wb_head;
1161                              lastreq = lastreq->wb_this_page)
1162                                 ;
1163
1164                         dupreq = nfs_create_request(req->wb_context,
1165                                         req->wb_page, lastreq, pgbase, bytes);
1166
1167                         if (IS_ERR(dupreq)) {
1168                                 nfs_page_group_unlock(req);
1169                                 return 0;
1170                         }
1171
1172                         nfs_lock_request(dupreq);
1173                         nfs_page_group_unlock(req);
1174                         dupreq->wb_offset = offset;
1175                         dupreq->wb_index = req->wb_index;
1176                 } else
1177                         dupreq = req;
1178
1179                 if (nfs_pgio_has_mirroring(desc))
1180                         desc->pg_mirror_idx = midx;
1181                 if (!nfs_pageio_add_request_mirror(desc, dupreq))
1182                         return 0;
1183         }
1184
1185         return 1;
1186 }
1187
1188 /*
1189  * nfs_pageio_complete_mirror - Complete I/O on the current mirror of an
1190  *                              nfs_pageio_descriptor
1191  * @desc: pointer to io descriptor
1192  */
1193 static void nfs_pageio_complete_mirror(struct nfs_pageio_descriptor *desc,
1194                                        u32 mirror_idx)
1195 {
1196         struct nfs_pgio_mirror *mirror = &desc->pg_mirrors[mirror_idx];
1197         u32 restore_idx = desc->pg_mirror_idx;
1198
1199         if (nfs_pgio_has_mirroring(desc))
1200                 desc->pg_mirror_idx = mirror_idx;
1201         for (;;) {
1202                 nfs_pageio_doio(desc);
1203                 if (!mirror->pg_recoalesce)
1204                         break;
1205                 if (!nfs_do_recoalesce(desc))
1206                         break;
1207         }
1208         desc->pg_mirror_idx = restore_idx;
1209 }
1210
1211 /*
1212  * nfs_pageio_resend - Transfer requests to new descriptor and resend
1213  * @hdr - the pgio header to move request from
1214  * @desc - the pageio descriptor to add requests to
1215  *
1216  * Try to move each request (nfs_page) from @hdr to @desc then attempt
1217  * to send them.
1218  *
1219  * Returns 0 on success and < 0 on error.
1220  */
1221 int nfs_pageio_resend(struct nfs_pageio_descriptor *desc,
1222                       struct nfs_pgio_header *hdr)
1223 {
1224         LIST_HEAD(failed);
1225
1226         desc->pg_dreq = hdr->dreq;
1227         while (!list_empty(&hdr->pages)) {
1228                 struct nfs_page *req = nfs_list_entry(hdr->pages.next);
1229
1230                 nfs_list_remove_request(req);
1231                 if (!nfs_pageio_add_request(desc, req))
1232                         nfs_list_add_request(req, &failed);
1233         }
1234         nfs_pageio_complete(desc);
1235         if (!list_empty(&failed)) {
1236                 list_move(&failed, &hdr->pages);
1237                 return -EIO;
1238         }
1239         return 0;
1240 }
1241 EXPORT_SYMBOL_GPL(nfs_pageio_resend);
1242
1243 /**
1244  * nfs_pageio_complete - Complete I/O then cleanup an nfs_pageio_descriptor
1245  * @desc: pointer to io descriptor
1246  */
1247 void nfs_pageio_complete(struct nfs_pageio_descriptor *desc)
1248 {
1249         u32 midx;
1250
1251         for (midx = 0; midx < desc->pg_mirror_count; midx++)
1252                 nfs_pageio_complete_mirror(desc, midx);
1253
1254         if (desc->pg_ops->pg_cleanup)
1255                 desc->pg_ops->pg_cleanup(desc);
1256         nfs_pageio_cleanup_mirroring(desc);
1257 }
1258
1259 /**
1260  * nfs_pageio_cond_complete - Conditional I/O completion
1261  * @desc: pointer to io descriptor
1262  * @index: page index
1263  *
1264  * It is important to ensure that processes don't try to take locks
1265  * on non-contiguous ranges of pages as that might deadlock. This
1266  * function should be called before attempting to wait on a locked
1267  * nfs_page. It will complete the I/O if the page index 'index'
1268  * is not contiguous with the existing list of pages in 'desc'.
1269  */
1270 void nfs_pageio_cond_complete(struct nfs_pageio_descriptor *desc, pgoff_t index)
1271 {
1272         struct nfs_pgio_mirror *mirror;
1273         struct nfs_page *prev;
1274         u32 midx;
1275
1276         for (midx = 0; midx < desc->pg_mirror_count; midx++) {
1277                 mirror = &desc->pg_mirrors[midx];
1278                 if (!list_empty(&mirror->pg_list)) {
1279                         prev = nfs_list_entry(mirror->pg_list.prev);
1280                         if (index != prev->wb_index + 1)
1281                                 nfs_pageio_complete_mirror(desc, midx);
1282                 }
1283         }
1284 }
1285
1286 int __init nfs_init_nfspagecache(void)
1287 {
1288         nfs_page_cachep = kmem_cache_create("nfs_page",
1289                                             sizeof(struct nfs_page),
1290                                             0, SLAB_HWCACHE_ALIGN,
1291                                             NULL);
1292         if (nfs_page_cachep == NULL)
1293                 return -ENOMEM;
1294
1295         return 0;
1296 }
1297
1298 void nfs_destroy_nfspagecache(void)
1299 {
1300         kmem_cache_destroy(nfs_page_cachep);
1301 }
1302
1303 static const struct rpc_call_ops nfs_pgio_common_ops = {
1304         .rpc_call_prepare = nfs_pgio_prepare,
1305         .rpc_call_done = nfs_pgio_result,
1306         .rpc_release = nfs_pgio_release,
1307 };
1308
1309 const struct nfs_pageio_ops nfs_pgio_rw_ops = {
1310         .pg_test = nfs_generic_pg_test,
1311         .pg_doio = nfs_generic_pg_pgios,
1312 };