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