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 static bool nfs_generic_pg_test(struct nfs_pageio_descriptor *desc, struct nfs_page *prev, struct nfs_page *req)
 208 {
 209         /*
 210          * FIXME: ideally we should be able to coalesce all requests
 211          * that are not block boundary aligned, but currently this
 212          * is problematic for the case of bsize < PAGE_CACHE_SIZE,
 213          * since nfs_flush_multi and nfs_pagein_multi assume you
 214          * can have only one struct nfs_page.
 215          */
 216         if (desc->pg_bsize < PAGE_SIZE)
 217                 return 0;
 218
 219         return desc->pg_count + req->wb_bytes <= desc->pg_bsize;
 220 }
 221
 222 /**
 223  * nfs_pageio_init - initialise a page io descriptor
 224  * @desc: pointer to descriptor
 225  * @inode: pointer to inode
 226  * @doio: pointer to io function
 227  * @bsize: io block size
 228  * @io_flags: extra parameters for the io function
 229  */
 230 void nfs_pageio_init(struct nfs_pageio_descriptor *desc,
 231                      struct inode *inode,
 232                      int (*doio)(struct nfs_pageio_descriptor *),
 233                      size_t bsize,
 234                      int io_flags)
 235 {
 236         INIT_LIST_HEAD(&desc->pg_list);
 237         desc->pg_bytes_written = 0;
 238         desc->pg_count = 0;
 239         desc->pg_bsize = bsize;
 240         desc->pg_base = 0;
 241         desc->pg_moreio = 0;
 242         desc->pg_inode = inode;
 243         desc->pg_doio = doio;
 244         desc->pg_ioflags = io_flags;
 245         desc->pg_error = 0;
 246         desc->pg_lseg = NULL;
 247         desc->pg_test = nfs_generic_pg_test;
 248         pnfs_pageio_init(desc, inode);
 249 }
 250
 251 /**
 252  * nfs_can_coalesce_requests - test two requests for compatibility
 253  * @prev: pointer to nfs_page
 254  * @req: pointer to nfs_page
 255  *
 256  * The nfs_page structures 'prev' and 'req' are compared to ensure that the
 257  * page data area they describe is contiguous, and that their RPC
 258  * credentials, NFSv4 open state, and lockowners are the same.
 259  *
 260  * Return 'true' if this is the case, else return 'false'.
 261  */
 262 static bool nfs_can_coalesce_requests(struct nfs_page *prev,
 263                                       struct nfs_page *req,
 264                                       struct nfs_pageio_descriptor *pgio)
 265 {
 266         if (req->wb_context->cred != prev->wb_context->cred)
 267                 return false;
 268         if (req->wb_lock_context->lockowner != prev->wb_lock_context->lockowner)
 269                 return false;
 270         if (req->wb_context->state != prev->wb_context->state)
 271                 return false;
 272         if (req->wb_index != (prev->wb_index + 1))
 273                 return false;
 274         if (req->wb_pgbase != 0)
 275                 return false;
 276         if (prev->wb_pgbase + prev->wb_bytes != PAGE_CACHE_SIZE)
 277                 return false;
 278         return pgio->pg_test(pgio, prev, req);
 279 }
 280
 281 /**
 282  * nfs_pageio_do_add_request - Attempt to coalesce a request into a page list.
 283  * @desc: destination io descriptor
 284  * @req: request
 285  *
 286  * Returns true if the request 'req' was successfully coalesced into the
 287  * existing list of pages 'desc'.
 288  */
 289 static int nfs_pageio_do_add_request(struct nfs_pageio_descriptor *desc,
 290                                      struct nfs_page *req)
 291 {
 292         if (desc->pg_count != 0) {
 293                 struct nfs_page *prev;
 294
 295                 prev = nfs_list_entry(desc->pg_list.prev);
 296                 if (!nfs_can_coalesce_requests(prev, req, desc))
 297                         return 0;
 298         } else {
 299                 desc->pg_base = req->wb_pgbase;
 300         }
 301         nfs_list_remove_request(req);
 302         nfs_list_add_request(req, &desc->pg_list);
 303         desc->pg_count += req->wb_bytes;
 304         return 1;
 305 }
 306
 307 /*
 308  * Helper for nfs_pageio_add_request and nfs_pageio_complete
 309  */
 310 static void nfs_pageio_doio(struct nfs_pageio_descriptor *desc)
 311 {
 312         if (!list_empty(&desc->pg_list)) {
 313                 int error = desc->pg_doio(desc);
 314                 if (error < 0)
 315                         desc->pg_error = error;
 316                 else
 317                         desc->pg_bytes_written += desc->pg_count;
 318         }
 319         if (list_empty(&desc->pg_list)) {
 320                 desc->pg_count = 0;
 321                 desc->pg_base = 0;
 322         }
 323 }
 324
 325 /**
 326  * nfs_pageio_add_request - Attempt to coalesce a request into a page list.
 327  * @desc: destination io descriptor
 328  * @req: request
 329  *
 330  * Returns true if the request 'req' was successfully coalesced into the
 331  * existing list of pages 'desc'.
 332  */
 333 int nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
 334                            struct nfs_page *req)
 335 {
 336         while (!nfs_pageio_do_add_request(desc, req)) {
 337                 desc->pg_moreio = 1;
 338                 nfs_pageio_doio(desc);
 339                 if (desc->pg_error < 0)
 340                         return 0;
 341                 desc->pg_moreio = 0;
 342         }
 343         return 1;
 344 }
 345
 346 /**
 347  * nfs_pageio_complete - Complete I/O on an nfs_pageio_descriptor
 348  * @desc: pointer to io descriptor
 349  */
 350 void nfs_pageio_complete(struct nfs_pageio_descriptor *desc)
 351 {
 352         nfs_pageio_doio(desc);
 353 }
 354
 355 /**
 356  * nfs_pageio_cond_complete - Conditional I/O completion
 357  * @desc: pointer to io descriptor
 358  * @index: page index
 359  *
 360  * It is important to ensure that processes don't try to take locks
 361  * on non-contiguous ranges of pages as that might deadlock. This
 362  * function should be called before attempting to wait on a locked
 363  * nfs_page. It will complete the I/O if the page index 'index'
 364  * is not contiguous with the existing list of pages in 'desc'.
 365  */
 366 void nfs_pageio_cond_complete(struct nfs_pageio_descriptor *desc, pgoff_t index)
 367 {
 368         if (!list_empty(&desc->pg_list)) {
 369                 struct nfs_page *prev = nfs_list_entry(desc->pg_list.prev);
 370                 if (index != prev->wb_index + 1)
 371                         nfs_pageio_doio(desc);
 372         }
 373 }
 374
 375 #define NFS_SCAN_MAXENTRIES 16
 376 /**
 377  * nfs_scan_list - Scan a list for matching requests
 378  * @nfsi: NFS inode
 379  * @dst: Destination list
 380  * @idx_start: lower bound of page->index to scan
 381  * @npages: idx_start + npages sets the upper bound to scan.
 382  * @tag: tag to scan for
 383  *
 384  * Moves elements from one of the inode request lists.
 385  * If the number of requests is set to 0, the entire address_space
 386  * starting at index idx_start, is scanned.
 387  * The requests are *not* checked to ensure that they form a contiguous set.
 388  * You must be holding the inode's i_lock when calling this function
 389  */
 390 int nfs_scan_list(struct nfs_inode *nfsi,
 391                 struct list_head *dst, pgoff_t idx_start,
 392                 unsigned int npages, int tag)
 393 {
 394         struct nfs_page *pgvec[NFS_SCAN_MAXENTRIES];
 395         struct nfs_page *req;
 396         pgoff_t idx_end;
 397         int found, i;
 398         int res;
 399         struct list_head *list;
 400
 401         res = 0;
 402         if (npages == 0)
 403                 idx_end = ~0;
 404         else
 405                 idx_end = idx_start + npages - 1;
 406
 407         for (;;) {
 408                 found = radix_tree_gang_lookup_tag(&nfsi->nfs_page_tree,
 409                                 (void **)&pgvec[0], idx_start,
 410                                 NFS_SCAN_MAXENTRIES, tag);
 411                 if (found <= 0)
 412                         break;
 413                 for (i = 0; i < found; i++) {
 414                         req = pgvec[i];
 415                         if (req->wb_index > idx_end)
 416                                 goto out;
 417                         idx_start = req->wb_index + 1;
 418                         if (nfs_set_page_tag_locked(req)) {
 419                                 kref_get(&req->wb_kref);
 420                                 radix_tree_tag_clear(&nfsi->nfs_page_tree,
 421                                                 req->wb_index, tag);
 422                                 list = pnfs_choose_commit_list(req, dst);
 423                                 nfs_list_add_request(req, list);
 424                                 res++;
 425                                 if (res == INT_MAX)
 426                                         goto out;
 427                         }
 428                 }
 429                 /* for latency reduction */
 430                 cond_resched_lock(&nfsi->vfs_inode.i_lock);
 431         }
 432 out:
 433         return res;
 434 }
 435
 436 int __init nfs_init_nfspagecache(void)
 437 {
 438         nfs_page_cachep = kmem_cache_create("nfs_page",
 439                                             sizeof(struct nfs_page),
 440                                             0, SLAB_HWCACHE_ALIGN,
 441                                             NULL);
 442         if (nfs_page_cachep == NULL)
 443                 return -ENOMEM;
 444
 445         return 0;
 446 }
 447
 448 void nfs_destroy_nfspagecache(void)
 449 {
 450         kmem_cache_destroy(nfs_page_cachep);
 451 }
 452