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 static struct kmem_cache *nfs_page_cachep;
  28
  29 bool nfs_pgarray_set(struct nfs_page_array *p, unsigned int pagecount)
  30 {
  31         p->npages = pagecount;
  32         if (pagecount <= ARRAY_SIZE(p->page_array))
  33                 p->pagevec = p->page_array;
  34         else {
  35                 p->pagevec = kcalloc(pagecount, sizeof(struct page *), GFP_KERNEL);
  36                 if (!p->pagevec)
  37                         p->npages = 0;
  38         }
  39         return p->pagevec != NULL;
  40 }
  41
  42 void nfs_pgheader_init(struct nfs_pageio_descriptor *desc,
  43                        struct nfs_pgio_header *hdr,
  44                        void (*release)(struct nfs_pgio_header *hdr))
  45 {
  46         hdr->req = nfs_list_entry(desc->pg_list.next);
  47         hdr->inode = desc->pg_inode;
  48         hdr->cred = hdr->req->wb_context->cred;
  49         hdr->io_start = req_offset(hdr->req);
  50         hdr->good_bytes = desc->pg_count;
  51         hdr->dreq = desc->pg_dreq;
  52         hdr->layout_private = desc->pg_layout_private;
  53         hdr->release = release;
  54         hdr->completion_ops = desc->pg_completion_ops;
  55         if (hdr->completion_ops->init_hdr)
  56                 hdr->completion_ops->init_hdr(hdr);
  57 }
  58 EXPORT_SYMBOL_GPL(nfs_pgheader_init);
  59
  60 void nfs_set_pgio_error(struct nfs_pgio_header *hdr, int error, loff_t pos)
  61 {
  62         spin_lock(&hdr->lock);
  63         if (pos < hdr->io_start + hdr->good_bytes) {
  64                 set_bit(NFS_IOHDR_ERROR, &hdr->flags);
  65                 clear_bit(NFS_IOHDR_EOF, &hdr->flags);
  66                 hdr->good_bytes = pos - hdr->io_start;
  67                 hdr->error = error;
  68         }
  69         spin_unlock(&hdr->lock);
  70 }
  71
  72 static inline struct nfs_page *
  73 nfs_page_alloc(void)
  74 {
  75         struct nfs_page *p = kmem_cache_zalloc(nfs_page_cachep, GFP_NOIO);
  76         if (p)
  77                 INIT_LIST_HEAD(&p->wb_list);
  78         return p;
  79 }
  80
  81 static inline void
  82 nfs_page_free(struct nfs_page *p)
  83 {
  84         kmem_cache_free(nfs_page_cachep, p);
  85 }
  86
  87 static void
  88 nfs_iocounter_inc(struct nfs_io_counter *c)
  89 {
  90         atomic_inc(&c->io_count);
  91 }
  92
  93 static void
  94 nfs_iocounter_dec(struct nfs_io_counter *c)
  95 {
  96         if (atomic_dec_and_test(&c->io_count)) {
  97                 clear_bit(NFS_IO_INPROGRESS, &c->flags);
  98                 smp_mb__after_atomic();
  99                 wake_up_bit(&c->flags, NFS_IO_INPROGRESS);
 100         }
 101 }
 102
 103 static int
 104 __nfs_iocounter_wait(struct nfs_io_counter *c)
 105 {
 106         wait_queue_head_t *wq = bit_waitqueue(&c->flags, NFS_IO_INPROGRESS);
 107         DEFINE_WAIT_BIT(q, &c->flags, NFS_IO_INPROGRESS);
 108         int ret = 0;
 109
 110         do {
 111                 prepare_to_wait(wq, &q.wait, TASK_KILLABLE);
 112                 set_bit(NFS_IO_INPROGRESS, &c->flags);
 113                 if (atomic_read(&c->io_count) == 0)
 114                         break;
 115                 ret = nfs_wait_bit_killable(&c->flags);
 116         } while (atomic_read(&c->io_count) != 0);
 117         finish_wait(wq, &q.wait);
 118         return ret;
 119 }
 120
 121 /**
 122  * nfs_iocounter_wait - wait for i/o to complete
 123  * @c: nfs_io_counter to use
 124  *
 125  * returns -ERESTARTSYS if interrupted by a fatal signal.
 126  * Otherwise returns 0 once the io_count hits 0.
 127  */
 128 int
 129 nfs_iocounter_wait(struct nfs_io_counter *c)
 130 {
 131         if (atomic_read(&c->io_count) == 0)
 132                 return 0;
 133         return __nfs_iocounter_wait(c);
 134 }
 135
 136 /**
 137  * nfs_create_request - Create an NFS read/write request.
 138  * @ctx: open context to use
 139  * @inode: inode to which the request is attached
 140  * @page: page to write
 141  * @offset: starting offset within the page for the write
 142  * @count: number of bytes to read/write
 143  *
 144  * The page must be locked by the caller. This makes sure we never
 145  * create two different requests for the same page.
 146  * User should ensure it is safe to sleep in this function.
 147  */
 148 struct nfs_page *
 149 nfs_create_request(struct nfs_open_context *ctx, struct inode *inode,
 150                    struct page *page,
 151                    unsigned int offset, unsigned int count)
 152 {
 153         struct nfs_page         *req;
 154         struct nfs_lock_context *l_ctx;
 155
 156         if (test_bit(NFS_CONTEXT_BAD, &ctx->flags))
 157                 return ERR_PTR(-EBADF);
 158         /* try to allocate the request struct */
 159         req = nfs_page_alloc();
 160         if (req == NULL)
 161                 return ERR_PTR(-ENOMEM);
 162
 163         /* get lock context early so we can deal with alloc failures */
 164         l_ctx = nfs_get_lock_context(ctx);
 165         if (IS_ERR(l_ctx)) {
 166                 nfs_page_free(req);
 167                 return ERR_CAST(l_ctx);
 168         }
 169         req->wb_lock_context = l_ctx;
 170         nfs_iocounter_inc(&l_ctx->io_count);
 171
 172         /* Initialize the request struct. Initially, we assume a
 173          * long write-back delay. This will be adjusted in
 174          * update_nfs_request below if the region is not locked. */
 175         req->wb_page    = page;
 176         req->wb_index   = page_file_index(page);
 177         page_cache_get(page);
 178         req->wb_offset  = offset;
 179         req->wb_pgbase  = offset;
 180         req->wb_bytes   = count;
 181         req->wb_context = get_nfs_open_context(ctx);
 182         kref_init(&req->wb_kref);
 183         return req;
 184 }
 185
 186 /**
 187  * nfs_unlock_request - Unlock request and wake up sleepers.
 188  * @req:
 189  */
 190 void nfs_unlock_request(struct nfs_page *req)
 191 {
 192         if (!NFS_WBACK_BUSY(req)) {
 193                 printk(KERN_ERR "NFS: Invalid unlock attempted\n");
 194                 BUG();
 195         }
 196         smp_mb__before_atomic();
 197         clear_bit(PG_BUSY, &req->wb_flags);
 198         smp_mb__after_atomic();
 199         wake_up_bit(&req->wb_flags, PG_BUSY);
 200 }
 201
 202 /**
 203  * nfs_unlock_and_release_request - Unlock request and release the nfs_page
 204  * @req:
 205  */
 206 void nfs_unlock_and_release_request(struct nfs_page *req)
 207 {
 208         nfs_unlock_request(req);
 209         nfs_release_request(req);
 210 }
 211
 212 /*
 213  * nfs_clear_request - Free up all resources allocated to the request
 214  * @req:
 215  *
 216  * Release page and open context resources associated with a read/write
 217  * request after it has completed.
 218  */
 219 static void nfs_clear_request(struct nfs_page *req)
 220 {
 221         struct page *page = req->wb_page;
 222         struct nfs_open_context *ctx = req->wb_context;
 223         struct nfs_lock_context *l_ctx = req->wb_lock_context;
 224
 225         if (page != NULL) {
 226                 page_cache_release(page);
 227                 req->wb_page = NULL;
 228         }
 229         if (l_ctx != NULL) {
 230                 nfs_iocounter_dec(&l_ctx->io_count);
 231                 nfs_put_lock_context(l_ctx);
 232                 req->wb_lock_context = NULL;
 233         }
 234         if (ctx != NULL) {
 235                 put_nfs_open_context(ctx);
 236                 req->wb_context = NULL;
 237         }
 238 }
 239
 240
 241 /**
 242  * nfs_release_request - Release the count on an NFS read/write request
 243  * @req: request to release
 244  *
 245  * Note: Should never be called with the spinlock held!
 246  */
 247 static void nfs_free_request(struct kref *kref)
 248 {
 249         struct nfs_page *req = container_of(kref, struct nfs_page, wb_kref);
 250
 251         /* Release struct file and open context */
 252         nfs_clear_request(req);
 253         nfs_page_free(req);
 254 }
 255
 256 void nfs_release_request(struct nfs_page *req)
 257 {
 258         kref_put(&req->wb_kref, nfs_free_request);
 259 }
 260
 261 static int nfs_wait_bit_uninterruptible(void *word)
 262 {
 263         io_schedule();
 264         return 0;
 265 }
 266
 267 /**
 268  * nfs_wait_on_request - Wait for a request to complete.
 269  * @req: request to wait upon.
 270  *
 271  * Interruptible by fatal signals only.
 272  * The user is responsible for holding a count on the request.
 273  */
 274 int
 275 nfs_wait_on_request(struct nfs_page *req)
 276 {
 277         return wait_on_bit(&req->wb_flags, PG_BUSY,
 278                         nfs_wait_bit_uninterruptible,
 279                         TASK_UNINTERRUPTIBLE);
 280 }
 281
 282 bool nfs_generic_pg_test(struct nfs_pageio_descriptor *desc, struct nfs_page *prev, struct nfs_page *req)
 283 {
 284         /*
 285          * FIXME: ideally we should be able to coalesce all requests
 286          * that are not block boundary aligned, but currently this
 287          * is problematic for the case of bsize < PAGE_CACHE_SIZE,
 288          * since nfs_flush_multi and nfs_pagein_multi assume you
 289          * can have only one struct nfs_page.
 290          */
 291         if (desc->pg_bsize < PAGE_SIZE)
 292                 return 0;
 293
 294         return desc->pg_count + req->wb_bytes <= desc->pg_bsize;
 295 }
 296 EXPORT_SYMBOL_GPL(nfs_generic_pg_test);
 297
 298 /**
 299  * nfs_pageio_init - initialise a page io descriptor
 300  * @desc: pointer to descriptor
 301  * @inode: pointer to inode
 302  * @doio: pointer to io function
 303  * @bsize: io block size
 304  * @io_flags: extra parameters for the io function
 305  */
 306 void nfs_pageio_init(struct nfs_pageio_descriptor *desc,
 307                      struct inode *inode,
 308                      const struct nfs_pageio_ops *pg_ops,
 309                      const struct nfs_pgio_completion_ops *compl_ops,
 310                      size_t bsize,
 311                      int io_flags)
 312 {
 313         INIT_LIST_HEAD(&desc->pg_list);
 314         desc->pg_bytes_written = 0;
 315         desc->pg_count = 0;
 316         desc->pg_bsize = bsize;
 317         desc->pg_base = 0;
 318         desc->pg_moreio = 0;
 319         desc->pg_recoalesce = 0;
 320         desc->pg_inode = inode;
 321         desc->pg_ops = pg_ops;
 322         desc->pg_completion_ops = compl_ops;
 323         desc->pg_ioflags = io_flags;
 324         desc->pg_error = 0;
 325         desc->pg_lseg = NULL;
 326         desc->pg_dreq = NULL;
 327         desc->pg_layout_private = NULL;
 328 }
 329 EXPORT_SYMBOL_GPL(nfs_pageio_init);
 330
 331 static bool nfs_match_open_context(const struct nfs_open_context *ctx1,
 332                 const struct nfs_open_context *ctx2)
 333 {
 334         return ctx1->cred == ctx2->cred && ctx1->state == ctx2->state;
 335 }
 336
 337 static bool nfs_match_lock_context(const struct nfs_lock_context *l1,
 338                 const struct nfs_lock_context *l2)
 339 {
 340         return l1->lockowner.l_owner == l2->lockowner.l_owner
 341                 && l1->lockowner.l_pid == l2->lockowner.l_pid;
 342 }
 343
 344 /**
 345  * nfs_can_coalesce_requests - test two requests for compatibility
 346  * @prev: pointer to nfs_page
 347  * @req: pointer to nfs_page
 348  *
 349  * The nfs_page structures 'prev' and 'req' are compared to ensure that the
 350  * page data area they describe is contiguous, and that their RPC
 351  * credentials, NFSv4 open state, and lockowners are the same.
 352  *
 353  * Return 'true' if this is the case, else return 'false'.
 354  */
 355 static bool nfs_can_coalesce_requests(struct nfs_page *prev,
 356                                       struct nfs_page *req,
 357                                       struct nfs_pageio_descriptor *pgio)
 358 {
 359         if (!nfs_match_open_context(req->wb_context, prev->wb_context))
 360                 return false;
 361         if (req->wb_context->dentry->d_inode->i_flock != NULL &&
 362             !nfs_match_lock_context(req->wb_lock_context, prev->wb_lock_context))
 363                 return false;
 364         if (req->wb_pgbase != 0)
 365                 return false;
 366         if (prev->wb_pgbase + prev->wb_bytes != PAGE_CACHE_SIZE)
 367                 return false;
 368         if (req_offset(req) != req_offset(prev) + prev->wb_bytes)
 369                 return false;
 370         return pgio->pg_ops->pg_test(pgio, prev, req);
 371 }
 372
 373 /**
 374  * nfs_pageio_do_add_request - Attempt to coalesce a request into a page list.
 375  * @desc: destination io descriptor
 376  * @req: request
 377  *
 378  * Returns true if the request 'req' was successfully coalesced into the
 379  * existing list of pages 'desc'.
 380  */
 381 static int nfs_pageio_do_add_request(struct nfs_pageio_descriptor *desc,
 382                                      struct nfs_page *req)
 383 {
 384         if (desc->pg_count != 0) {
 385                 struct nfs_page *prev;
 386
 387                 prev = nfs_list_entry(desc->pg_list.prev);
 388                 if (!nfs_can_coalesce_requests(prev, req, desc))
 389                         return 0;
 390         } else {
 391                 if (desc->pg_ops->pg_init)
 392                         desc->pg_ops->pg_init(desc, req);
 393                 desc->pg_base = req->wb_pgbase;
 394         }
 395         nfs_list_remove_request(req);
 396         nfs_list_add_request(req, &desc->pg_list);
 397         desc->pg_count += req->wb_bytes;
 398         return 1;
 399 }
 400
 401 /*
 402  * Helper for nfs_pageio_add_request and nfs_pageio_complete
 403  */
 404 static void nfs_pageio_doio(struct nfs_pageio_descriptor *desc)
 405 {
 406         if (!list_empty(&desc->pg_list)) {
 407                 int error = desc->pg_ops->pg_doio(desc);
 408                 if (error < 0)
 409                         desc->pg_error = error;
 410                 else
 411                         desc->pg_bytes_written += desc->pg_count;
 412         }
 413         if (list_empty(&desc->pg_list)) {
 414                 desc->pg_count = 0;
 415                 desc->pg_base = 0;
 416         }
 417 }
 418
 419 /**
 420  * nfs_pageio_add_request - Attempt to coalesce a request into a page list.
 421  * @desc: destination io descriptor
 422  * @req: request
 423  *
 424  * Returns true if the request 'req' was successfully coalesced into the
 425  * existing list of pages 'desc'.
 426  */
 427 static int __nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
 428                            struct nfs_page *req)
 429 {
 430         while (!nfs_pageio_do_add_request(desc, req)) {
 431                 desc->pg_moreio = 1;
 432                 nfs_pageio_doio(desc);
 433                 if (desc->pg_error < 0)
 434                         return 0;
 435                 desc->pg_moreio = 0;
 436                 if (desc->pg_recoalesce)
 437                         return 0;
 438         }
 439         return 1;
 440 }
 441
 442 static int nfs_do_recoalesce(struct nfs_pageio_descriptor *desc)
 443 {
 444         LIST_HEAD(head);
 445
 446         do {
 447                 list_splice_init(&desc->pg_list, &head);
 448                 desc->pg_bytes_written -= desc->pg_count;
 449                 desc->pg_count = 0;
 450                 desc->pg_base = 0;
 451                 desc->pg_recoalesce = 0;
 452
 453                 while (!list_empty(&head)) {
 454                         struct nfs_page *req;
 455
 456                         req = list_first_entry(&head, struct nfs_page, wb_list);
 457                         nfs_list_remove_request(req);
 458                         if (__nfs_pageio_add_request(desc, req))
 459                                 continue;
 460                         if (desc->pg_error < 0)
 461                                 return 0;
 462                         break;
 463                 }
 464         } while (desc->pg_recoalesce);
 465         return 1;
 466 }
 467
 468 int nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
 469                 struct nfs_page *req)
 470 {
 471         int ret;
 472
 473         do {
 474                 ret = __nfs_pageio_add_request(desc, req);
 475                 if (ret)
 476                         break;
 477                 if (desc->pg_error < 0)
 478                         break;
 479                 ret = nfs_do_recoalesce(desc);
 480         } while (ret);
 481         return ret;
 482 }
 483 EXPORT_SYMBOL_GPL(nfs_pageio_add_request);
 484
 485 /**
 486  * nfs_pageio_complete - Complete I/O on an nfs_pageio_descriptor
 487  * @desc: pointer to io descriptor
 488  */
 489 void nfs_pageio_complete(struct nfs_pageio_descriptor *desc)
 490 {
 491         for (;;) {
 492                 nfs_pageio_doio(desc);
 493                 if (!desc->pg_recoalesce)
 494                         break;
 495                 if (!nfs_do_recoalesce(desc))
 496                         break;
 497         }
 498 }
 499 EXPORT_SYMBOL_GPL(nfs_pageio_complete);
 500
 501 /**
 502  * nfs_pageio_cond_complete - Conditional I/O completion
 503  * @desc: pointer to io descriptor
 504  * @index: page index
 505  *
 506  * It is important to ensure that processes don't try to take locks
 507  * on non-contiguous ranges of pages as that might deadlock. This
 508  * function should be called before attempting to wait on a locked
 509  * nfs_page. It will complete the I/O if the page index 'index'
 510  * is not contiguous with the existing list of pages in 'desc'.
 511  */
 512 void nfs_pageio_cond_complete(struct nfs_pageio_descriptor *desc, pgoff_t index)
 513 {
 514         if (!list_empty(&desc->pg_list)) {
 515                 struct nfs_page *prev = nfs_list_entry(desc->pg_list.prev);
 516                 if (index != prev->wb_index + 1)
 517                         nfs_pageio_complete(desc);
 518         }
 519 }
 520
 521 int __init nfs_init_nfspagecache(void)
 522 {
 523         nfs_page_cachep = kmem_cache_create("nfs_page",
 524                                             sizeof(struct nfs_page),
 525                                             0, SLAB_HWCACHE_ALIGN,
 526                                             NULL);
 527         if (nfs_page_cachep == NULL)
 528                 return -ENOMEM;
 529
 530         return 0;
 531 }
 532
 533 void nfs_destroy_nfspagecache(void)
 534 {
 535         kmem_cache_destroy(nfs_page_cachep);
 536 }
 537