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/nfs3.h>
  17 #include <linux/nfs4.h>
  18 #include <linux/nfs_page.h>
  19 #include <linux/nfs_fs.h>
  20 #include <linux/nfs_mount.h>
  21
  22 #include "internal.h"
  23 #include "pnfs.h"
  24
  25 static struct kmem_cache *nfs_page_cachep;
  26
  27 static inline struct nfs_page *
  28 nfs_page_alloc(void)
  29 {
  30         struct nfs_page *p = kmem_cache_zalloc(nfs_page_cachep, GFP_KERNEL);
  31         if (p)
  32                 INIT_LIST_HEAD(&p->wb_list);
  33         return p;
  34 }
  35
  36 static inline void
  37 nfs_page_free(struct nfs_page *p)
  38 {
  39         kmem_cache_free(nfs_page_cachep, p);
  40 }
  41
  42 /**
  43  * nfs_create_request - Create an NFS read/write request.
  44  * @file: file descriptor to use
  45  * @inode: inode to which the request is attached
  46  * @page: page to write
  47  * @offset: starting offset within the page for the write
  48  * @count: number of bytes to read/write
  49  *
  50  * The page must be locked by the caller. This makes sure we never
  51  * create two different requests for the same page.
  52  * User should ensure it is safe to sleep in this function.
  53  */
  54 struct nfs_page *
  55 nfs_create_request(struct nfs_open_context *ctx, struct inode *inode,
  56                    struct page *page,
  57                    unsigned int offset, unsigned int count)
  58 {
  59         struct nfs_page         *req;
  60
  61         /* try to allocate the request struct */
  62         req = nfs_page_alloc();
  63         if (req == NULL)
  64                 return ERR_PTR(-ENOMEM);
  65
  66         /* get lock context early so we can deal with alloc failures */
  67         req->wb_lock_context = nfs_get_lock_context(ctx);
  68         if (req->wb_lock_context == NULL) {
  69                 nfs_page_free(req);
  70                 return ERR_PTR(-ENOMEM);
  71         }
  72
  73         /* Initialize the request struct. Initially, we assume a
  74          * long write-back delay. This will be adjusted in
  75          * update_nfs_request below if the region is not locked. */
  76         req->wb_page    = page;
  77         atomic_set(&req->wb_complete, 0);
  78         req->wb_index   = page->index;
  79         page_cache_get(page);
  80         BUG_ON(PagePrivate(page));
  81         BUG_ON(!PageLocked(page));
  82         BUG_ON(page->mapping->host != inode);
  83         req->wb_offset  = offset;
  84         req->wb_pgbase  = offset;
  85         req->wb_bytes   = count;
  86         req->wb_context = get_nfs_open_context(ctx);
  87         kref_init(&req->wb_kref);
  88         return req;
  89 }
  90
  91 /**
  92  * nfs_unlock_request - Unlock request and wake up sleepers.
  93  * @req:
  94  */
  95 void nfs_unlock_request(struct nfs_page *req)
  96 {
  97         if (!NFS_WBACK_BUSY(req)) {
  98                 printk(KERN_ERR "NFS: Invalid unlock attempted\n");
  99                 BUG();
 100         }
 101         smp_mb__before_clear_bit();
 102         clear_bit(PG_BUSY, &req->wb_flags);
 103         smp_mb__after_clear_bit();
 104         wake_up_bit(&req->wb_flags, PG_BUSY);
 105         nfs_release_request(req);
 106 }
 107
 108 /**
 109  * nfs_set_page_tag_locked - Tag a request as locked
 110  * @req:
 111  */
 112 int nfs_set_page_tag_locked(struct nfs_page *req)
 113 {
 114         if (!nfs_lock_request_dontget(req))
 115                 return 0;
 116         if (test_bit(PG_MAPPED, &req->wb_flags))
 117                 radix_tree_tag_set(&NFS_I(req->wb_context->path.dentry->d_inode)->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_LOCKED);
 118         return 1;
 119 }
 120
 121 /**
 122  * nfs_clear_page_tag_locked - Clear request tag and wake up sleepers
 123  */
 124 void nfs_clear_page_tag_locked(struct nfs_page *req)
 125 {
 126         if (test_bit(PG_MAPPED, &req->wb_flags)) {
 127                 struct inode *inode = req->wb_context->path.dentry->d_inode;
 128                 struct nfs_inode *nfsi = NFS_I(inode);
 129
 130                 spin_lock(&inode->i_lock);
 131                 radix_tree_tag_clear(&nfsi->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_LOCKED);
 132                 nfs_unlock_request(req);
 133                 spin_unlock(&inode->i_lock);
 134         } else
 135                 nfs_unlock_request(req);
 136 }
 137
 138 /*
 139  * nfs_clear_request - Free up all resources allocated to the request
 140  * @req:
 141  *
 142  * Release page and open context resources associated with a read/write
 143  * request after it has completed.
 144  */
 145 static void nfs_clear_request(struct nfs_page *req)
 146 {
 147         struct page *page = req->wb_page;
 148         struct nfs_open_context *ctx = req->wb_context;
 149         struct nfs_lock_context *l_ctx = req->wb_lock_context;
 150
 151         if (page != NULL) {
 152                 page_cache_release(page);
 153                 req->wb_page = NULL;
 154         }
 155         if (l_ctx != NULL) {
 156                 nfs_put_lock_context(l_ctx);
 157                 req->wb_lock_context = NULL;
 158         }
 159         if (ctx != NULL) {
 160                 put_nfs_open_context(ctx);
 161                 req->wb_context = NULL;
 162         }
 163 }
 164
 165
 166 /**
 167  * nfs_release_request - Release the count on an NFS read/write request
 168  * @req: request to release
 169  *
 170  * Note: Should never be called with the spinlock held!
 171  */
 172 static void nfs_free_request(struct kref *kref)
 173 {
 174         struct nfs_page *req = container_of(kref, struct nfs_page, wb_kref);
 175
 176         /* Release struct file and open context */
 177         nfs_clear_request(req);
 178         nfs_page_free(req);
 179 }
 180
 181 void nfs_release_request(struct nfs_page *req)
 182 {
 183         kref_put(&req->wb_kref, nfs_free_request);
 184 }
 185
 186 static int nfs_wait_bit_uninterruptible(void *word)
 187 {
 188         io_schedule();
 189         return 0;
 190 }
 191
 192 /**
 193  * nfs_wait_on_request - Wait for a request to complete.
 194  * @req: request to wait upon.
 195  *
 196  * Interruptible by fatal signals only.
 197  * The user is responsible for holding a count on the request.
 198  */
 199 int
 200 nfs_wait_on_request(struct nfs_page *req)
 201 {
 202         return wait_on_bit(&req->wb_flags, PG_BUSY,
 203                         nfs_wait_bit_uninterruptible,
 204                         TASK_UNINTERRUPTIBLE);
 205 }
 206
 207 /**
 208  * nfs_pageio_init - initialise a page io descriptor
 209  * @desc: pointer to descriptor
 210  * @inode: pointer to inode
 211  * @doio: pointer to io function
 212  * @bsize: io block size
 213  * @io_flags: extra parameters for the io function
 214  */
 215 void nfs_pageio_init(struct nfs_pageio_descriptor *desc,
 216                      struct inode *inode,
 217                      int (*doio)(struct nfs_pageio_descriptor *),
 218                      size_t bsize,
 219                      int io_flags)
 220 {
 221         INIT_LIST_HEAD(&desc->pg_list);
 222         desc->pg_bytes_written = 0;
 223         desc->pg_count = 0;
 224         desc->pg_bsize = bsize;
 225         desc->pg_base = 0;
 226         desc->pg_moreio = 0;
 227         desc->pg_inode = inode;
 228         desc->pg_doio = doio;
 229         desc->pg_ioflags = io_flags;
 230         desc->pg_error = 0;
 231         desc->pg_lseg = NULL;
 232 }
 233
 234 /**
 235  * nfs_can_coalesce_requests - test two requests for compatibility
 236  * @prev: pointer to nfs_page
 237  * @req: pointer to nfs_page
 238  *
 239  * The nfs_page structures 'prev' and 'req' are compared to ensure that the
 240  * page data area they describe is contiguous, and that their RPC
 241  * credentials, NFSv4 open state, and lockowners are the same.
 242  *
 243  * Return 'true' if this is the case, else return 'false'.
 244  */
 245 static int nfs_can_coalesce_requests(struct nfs_page *prev,
 246                                      struct nfs_page *req,
 247                                      struct nfs_pageio_descriptor *pgio)
 248 {
 249         if (req->wb_context->cred != prev->wb_context->cred)
 250                 return 0;
 251         if (req->wb_lock_context->lockowner != prev->wb_lock_context->lockowner)
 252                 return 0;
 253         if (req->wb_context->state != prev->wb_context->state)
 254                 return 0;
 255         if (req->wb_index != (prev->wb_index + 1))
 256                 return 0;
 257         if (req->wb_pgbase != 0)
 258                 return 0;
 259         if (prev->wb_pgbase + prev->wb_bytes != PAGE_CACHE_SIZE)
 260                 return 0;
 261         /*
 262          * Non-whole file layouts need to check that req is inside of
 263          * pgio->pg_lseg.
 264          */
 265         if (pgio->pg_test && !pgio->pg_test(pgio, prev, req))
 266                 return 0;
 267         return 1;
 268 }
 269
 270 /**
 271  * nfs_pageio_do_add_request - Attempt to coalesce a request into a page list.
 272  * @desc: destination io descriptor
 273  * @req: request
 274  *
 275  * Returns true if the request 'req' was successfully coalesced into the
 276  * existing list of pages 'desc'.
 277  */
 278 static int nfs_pageio_do_add_request(struct nfs_pageio_descriptor *desc,
 279                                      struct nfs_page *req)
 280 {
 281         size_t newlen = req->wb_bytes;
 282
 283         if (desc->pg_count != 0) {
 284                 struct nfs_page *prev;
 285
 286                 /*
 287                  * FIXME: ideally we should be able to coalesce all requests
 288                  * that are not block boundary aligned, but currently this
 289                  * is problematic for the case of bsize < PAGE_CACHE_SIZE,
 290                  * since nfs_flush_multi and nfs_pagein_multi assume you
 291                  * can have only one struct nfs_page.
 292                  */
 293                 if (desc->pg_bsize < PAGE_SIZE)
 294                         return 0;
 295                 newlen += desc->pg_count;
 296                 if (newlen > desc->pg_bsize)
 297                         return 0;
 298                 prev = nfs_list_entry(desc->pg_list.prev);
 299                 if (!nfs_can_coalesce_requests(prev, req, desc))
 300                         return 0;
 301         } else
 302                 desc->pg_base = req->wb_pgbase;
 303         nfs_list_remove_request(req);
 304         nfs_list_add_request(req, &desc->pg_list);
 305         desc->pg_count = newlen;
 306         return 1;
 307 }
 308
 309 /*
 310  * Helper for nfs_pageio_add_request and nfs_pageio_complete
 311  */
 312 static void nfs_pageio_doio(struct nfs_pageio_descriptor *desc)
 313 {
 314         if (!list_empty(&desc->pg_list)) {
 315                 int error = desc->pg_doio(desc);
 316                 if (error < 0)
 317                         desc->pg_error = error;
 318                 else
 319                         desc->pg_bytes_written += desc->pg_count;
 320         }
 321         if (list_empty(&desc->pg_list)) {
 322                 desc->pg_count = 0;
 323                 desc->pg_base = 0;
 324         }
 325 }
 326
 327 /**
 328  * nfs_pageio_add_request - Attempt to coalesce a request into a page list.
 329  * @desc: destination io descriptor
 330  * @req: request
 331  *
 332  * Returns true if the request 'req' was successfully coalesced into the
 333  * existing list of pages 'desc'.
 334  */
 335 int nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
 336                            struct nfs_page *req)
 337 {
 338         while (!nfs_pageio_do_add_request(desc, req)) {
 339                 desc->pg_moreio = 1;
 340                 nfs_pageio_doio(desc);
 341                 if (desc->pg_error < 0)
 342                         return 0;
 343                 desc->pg_moreio = 0;
 344         }
 345         return 1;
 346 }
 347
 348 /**
 349  * nfs_pageio_complete - Complete I/O on an nfs_pageio_descriptor
 350  * @desc: pointer to io descriptor
 351  */
 352 void nfs_pageio_complete(struct nfs_pageio_descriptor *desc)
 353 {
 354         nfs_pageio_doio(desc);
 355 }
 356
 357 /**
 358  * nfs_pageio_cond_complete - Conditional I/O completion
 359  * @desc: pointer to io descriptor
 360  * @index: page index
 361  *
 362  * It is important to ensure that processes don't try to take locks
 363  * on non-contiguous ranges of pages as that might deadlock. This
 364  * function should be called before attempting to wait on a locked
 365  * nfs_page. It will complete the I/O if the page index 'index'
 366  * is not contiguous with the existing list of pages in 'desc'.
 367  */
 368 void nfs_pageio_cond_complete(struct nfs_pageio_descriptor *desc, pgoff_t index)
 369 {
 370         if (!list_empty(&desc->pg_list)) {
 371                 struct nfs_page *prev = nfs_list_entry(desc->pg_list.prev);
 372                 if (index != prev->wb_index + 1)
 373                         nfs_pageio_doio(desc);
 374         }
 375 }
 376
 377 #define NFS_SCAN_MAXENTRIES 16
 378 /**
 379  * nfs_scan_list - Scan a list for matching requests
 380  * @nfsi: NFS inode
 381  * @dst: Destination list
 382  * @idx_start: lower bound of page->index to scan
 383  * @npages: idx_start + npages sets the upper bound to scan.
 384  * @tag: tag to scan for
 385  *
 386  * Moves elements from one of the inode request lists.
 387  * If the number of requests is set to 0, the entire address_space
 388  * starting at index idx_start, is scanned.
 389  * The requests are *not* checked to ensure that they form a contiguous set.
 390  * You must be holding the inode's i_lock when calling this function
 391  */
 392 int nfs_scan_list(struct nfs_inode *nfsi,
 393                 struct list_head *dst, pgoff_t idx_start,
 394                 unsigned int npages, int tag)
 395 {
 396         struct nfs_page *pgvec[NFS_SCAN_MAXENTRIES];
 397         struct nfs_page *req;
 398         pgoff_t idx_end;
 399         int found, i;
 400         int res;
 401         struct list_head *list;
 402
 403         res = 0;
 404         if (npages == 0)
 405                 idx_end = ~0;
 406         else
 407                 idx_end = idx_start + npages - 1;
 408
 409         for (;;) {
 410                 found = radix_tree_gang_lookup_tag(&nfsi->nfs_page_tree,
 411                                 (void **)&pgvec[0], idx_start,
 412                                 NFS_SCAN_MAXENTRIES, tag);
 413                 if (found <= 0)
 414                         break;
 415                 for (i = 0; i < found; i++) {
 416                         req = pgvec[i];
 417                         if (req->wb_index > idx_end)
 418                                 goto out;
 419                         idx_start = req->wb_index + 1;
 420                         if (nfs_set_page_tag_locked(req)) {
 421                                 kref_get(&req->wb_kref);
 422                                 radix_tree_tag_clear(&nfsi->nfs_page_tree,
 423                                                 req->wb_index, tag);
 424                                 list = pnfs_choose_commit_list(req, dst);
 425                                 nfs_list_add_request(req, list);
 426                                 res++;
 427                                 if (res == INT_MAX)
 428                                         goto out;
 429                         }
 430                 }
 431                 /* for latency reduction */
 432                 cond_resched_lock(&nfsi->vfs_inode.i_lock);
 433         }
 434 out:
 435         return res;
 436 }
 437
 438 int __init nfs_init_nfspagecache(void)
 439 {
 440         nfs_page_cachep = kmem_cache_create("nfs_page",
 441                                             sizeof(struct nfs_page),
 442                                             0, SLAB_HWCACHE_ALIGN,
 443                                             NULL);
 444         if (nfs_page_cachep == NULL)
 445                 return -ENOMEM;
 446
 447         return 0;
 448 }
 449
 450 void nfs_destroy_nfspagecache(void)
 451 {
 452         kmem_cache_destroy(nfs_page_cachep);
 453 }
 454