linux/fs/nfs/pagelist.c
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   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
  27static struct kmem_cache *nfs_page_cachep;
  28
  29bool 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
  42void 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}
  58EXPORT_SYMBOL_GPL(nfs_pgheader_init);
  59
  60void 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
  72static inline struct nfs_page *
  73nfs_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
  81static inline void
  82nfs_page_free(struct nfs_page *p)
  83{
  84        kmem_cache_free(nfs_page_cachep, p);
  85}
  86
  87/**
  88 * nfs_create_request - Create an NFS read/write request.
  89 * @ctx: open context to use
  90 * @inode: inode to which the request is attached
  91 * @page: page to write
  92 * @offset: starting offset within the page for the write
  93 * @count: number of bytes to read/write
  94 *
  95 * The page must be locked by the caller. This makes sure we never
  96 * create two different requests for the same page.
  97 * User should ensure it is safe to sleep in this function.
  98 */
  99struct nfs_page *
 100nfs_create_request(struct nfs_open_context *ctx, struct inode *inode,
 101                   struct page *page,
 102                   unsigned int offset, unsigned int count)
 103{
 104        struct nfs_page         *req;
 105
 106        /* try to allocate the request struct */
 107        req = nfs_page_alloc();
 108        if (req == NULL)
 109                return ERR_PTR(-ENOMEM);
 110
 111        /* get lock context early so we can deal with alloc failures */
 112        req->wb_lock_context = nfs_get_lock_context(ctx);
 113        if (req->wb_lock_context == NULL) {
 114                nfs_page_free(req);
 115                return ERR_PTR(-ENOMEM);
 116        }
 117
 118        /* Initialize the request struct. Initially, we assume a
 119         * long write-back delay. This will be adjusted in
 120         * update_nfs_request below if the region is not locked. */
 121        req->wb_page    = page;
 122        req->wb_index   = page_file_index(page);
 123        page_cache_get(page);
 124        req->wb_offset  = offset;
 125        req->wb_pgbase  = offset;
 126        req->wb_bytes   = count;
 127        req->wb_context = get_nfs_open_context(ctx);
 128        kref_init(&req->wb_kref);
 129        return req;
 130}
 131
 132/**
 133 * nfs_unlock_request - Unlock request and wake up sleepers.
 134 * @req:
 135 */
 136void nfs_unlock_request(struct nfs_page *req)
 137{
 138        if (!NFS_WBACK_BUSY(req)) {
 139                printk(KERN_ERR "NFS: Invalid unlock attempted\n");
 140                BUG();
 141        }
 142        smp_mb__before_clear_bit();
 143        clear_bit(PG_BUSY, &req->wb_flags);
 144        smp_mb__after_clear_bit();
 145        wake_up_bit(&req->wb_flags, PG_BUSY);
 146}
 147
 148/**
 149 * nfs_unlock_and_release_request - Unlock request and release the nfs_page
 150 * @req:
 151 */
 152void nfs_unlock_and_release_request(struct nfs_page *req)
 153{
 154        nfs_unlock_request(req);
 155        nfs_release_request(req);
 156}
 157
 158/*
 159 * nfs_clear_request - Free up all resources allocated to the request
 160 * @req:
 161 *
 162 * Release page and open context resources associated with a read/write
 163 * request after it has completed.
 164 */
 165static void nfs_clear_request(struct nfs_page *req)
 166{
 167        struct page *page = req->wb_page;
 168        struct nfs_open_context *ctx = req->wb_context;
 169        struct nfs_lock_context *l_ctx = req->wb_lock_context;
 170
 171        if (page != NULL) {
 172                page_cache_release(page);
 173                req->wb_page = NULL;
 174        }
 175        if (l_ctx != NULL) {
 176                nfs_put_lock_context(l_ctx);
 177                req->wb_lock_context = NULL;
 178        }
 179        if (ctx != NULL) {
 180                put_nfs_open_context(ctx);
 181                req->wb_context = NULL;
 182        }
 183}
 184
 185
 186/**
 187 * nfs_release_request - Release the count on an NFS read/write request
 188 * @req: request to release
 189 *
 190 * Note: Should never be called with the spinlock held!
 191 */
 192static void nfs_free_request(struct kref *kref)
 193{
 194        struct nfs_page *req = container_of(kref, struct nfs_page, wb_kref);
 195
 196        /* Release struct file and open context */
 197        nfs_clear_request(req);
 198        nfs_page_free(req);
 199}
 200
 201void nfs_release_request(struct nfs_page *req)
 202{
 203        kref_put(&req->wb_kref, nfs_free_request);
 204}
 205
 206static int nfs_wait_bit_uninterruptible(void *word)
 207{
 208        io_schedule();
 209        return 0;
 210}
 211
 212/**
 213 * nfs_wait_on_request - Wait for a request to complete.
 214 * @req: request to wait upon.
 215 *
 216 * Interruptible by fatal signals only.
 217 * The user is responsible for holding a count on the request.
 218 */
 219int
 220nfs_wait_on_request(struct nfs_page *req)
 221{
 222        return wait_on_bit(&req->wb_flags, PG_BUSY,
 223                        nfs_wait_bit_uninterruptible,
 224                        TASK_UNINTERRUPTIBLE);
 225}
 226
 227bool nfs_generic_pg_test(struct nfs_pageio_descriptor *desc, struct nfs_page *prev, struct nfs_page *req)
 228{
 229        /*
 230         * FIXME: ideally we should be able to coalesce all requests
 231         * that are not block boundary aligned, but currently this
 232         * is problematic for the case of bsize < PAGE_CACHE_SIZE,
 233         * since nfs_flush_multi and nfs_pagein_multi assume you
 234         * can have only one struct nfs_page.
 235         */
 236        if (desc->pg_bsize < PAGE_SIZE)
 237                return 0;
 238
 239        return desc->pg_count + req->wb_bytes <= desc->pg_bsize;
 240}
 241EXPORT_SYMBOL_GPL(nfs_generic_pg_test);
 242
 243/**
 244 * nfs_pageio_init - initialise a page io descriptor
 245 * @desc: pointer to descriptor
 246 * @inode: pointer to inode
 247 * @doio: pointer to io function
 248 * @bsize: io block size
 249 * @io_flags: extra parameters for the io function
 250 */
 251void nfs_pageio_init(struct nfs_pageio_descriptor *desc,
 252                     struct inode *inode,
 253                     const struct nfs_pageio_ops *pg_ops,
 254                     const struct nfs_pgio_completion_ops *compl_ops,
 255                     size_t bsize,
 256                     int io_flags)
 257{
 258        INIT_LIST_HEAD(&desc->pg_list);
 259        desc->pg_bytes_written = 0;
 260        desc->pg_count = 0;
 261        desc->pg_bsize = bsize;
 262        desc->pg_base = 0;
 263        desc->pg_moreio = 0;
 264        desc->pg_recoalesce = 0;
 265        desc->pg_inode = inode;
 266        desc->pg_ops = pg_ops;
 267        desc->pg_completion_ops = compl_ops;
 268        desc->pg_ioflags = io_flags;
 269        desc->pg_error = 0;
 270        desc->pg_lseg = NULL;
 271        desc->pg_dreq = NULL;
 272        desc->pg_layout_private = NULL;
 273}
 274EXPORT_SYMBOL_GPL(nfs_pageio_init);
 275
 276/**
 277 * nfs_can_coalesce_requests - test two requests for compatibility
 278 * @prev: pointer to nfs_page
 279 * @req: pointer to nfs_page
 280 *
 281 * The nfs_page structures 'prev' and 'req' are compared to ensure that the
 282 * page data area they describe is contiguous, and that their RPC
 283 * credentials, NFSv4 open state, and lockowners are the same.
 284 *
 285 * Return 'true' if this is the case, else return 'false'.
 286 */
 287static bool nfs_can_coalesce_requests(struct nfs_page *prev,
 288                                      struct nfs_page *req,
 289                                      struct nfs_pageio_descriptor *pgio)
 290{
 291        if (req->wb_context->cred != prev->wb_context->cred)
 292                return false;
 293        if (req->wb_lock_context->lockowner != prev->wb_lock_context->lockowner)
 294                return false;
 295        if (req->wb_context->state != prev->wb_context->state)
 296                return false;
 297        if (req->wb_pgbase != 0)
 298                return false;
 299        if (prev->wb_pgbase + prev->wb_bytes != PAGE_CACHE_SIZE)
 300                return false;
 301        if (req_offset(req) != req_offset(prev) + prev->wb_bytes)
 302                return false;
 303        return pgio->pg_ops->pg_test(pgio, prev, req);
 304}
 305
 306/**
 307 * nfs_pageio_do_add_request - Attempt to coalesce a request into a page list.
 308 * @desc: destination io descriptor
 309 * @req: request
 310 *
 311 * Returns true if the request 'req' was successfully coalesced into the
 312 * existing list of pages 'desc'.
 313 */
 314static int nfs_pageio_do_add_request(struct nfs_pageio_descriptor *desc,
 315                                     struct nfs_page *req)
 316{
 317        if (desc->pg_count != 0) {
 318                struct nfs_page *prev;
 319
 320                prev = nfs_list_entry(desc->pg_list.prev);
 321                if (!nfs_can_coalesce_requests(prev, req, desc))
 322                        return 0;
 323        } else {
 324                if (desc->pg_ops->pg_init)
 325                        desc->pg_ops->pg_init(desc, req);
 326                desc->pg_base = req->wb_pgbase;
 327        }
 328        nfs_list_remove_request(req);
 329        nfs_list_add_request(req, &desc->pg_list);
 330        desc->pg_count += req->wb_bytes;
 331        return 1;
 332}
 333
 334/*
 335 * Helper for nfs_pageio_add_request and nfs_pageio_complete
 336 */
 337static void nfs_pageio_doio(struct nfs_pageio_descriptor *desc)
 338{
 339        if (!list_empty(&desc->pg_list)) {
 340                int error = desc->pg_ops->pg_doio(desc);
 341                if (error < 0)
 342                        desc->pg_error = error;
 343                else
 344                        desc->pg_bytes_written += desc->pg_count;
 345        }
 346        if (list_empty(&desc->pg_list)) {
 347                desc->pg_count = 0;
 348                desc->pg_base = 0;
 349        }
 350}
 351
 352/**
 353 * nfs_pageio_add_request - Attempt to coalesce a request into a page list.
 354 * @desc: destination io descriptor
 355 * @req: request
 356 *
 357 * Returns true if the request 'req' was successfully coalesced into the
 358 * existing list of pages 'desc'.
 359 */
 360static int __nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
 361                           struct nfs_page *req)
 362{
 363        while (!nfs_pageio_do_add_request(desc, req)) {
 364                desc->pg_moreio = 1;
 365                nfs_pageio_doio(desc);
 366                if (desc->pg_error < 0)
 367                        return 0;
 368                desc->pg_moreio = 0;
 369                if (desc->pg_recoalesce)
 370                        return 0;
 371        }
 372        return 1;
 373}
 374
 375static int nfs_do_recoalesce(struct nfs_pageio_descriptor *desc)
 376{
 377        LIST_HEAD(head);
 378
 379        do {
 380                list_splice_init(&desc->pg_list, &head);
 381                desc->pg_bytes_written -= desc->pg_count;
 382                desc->pg_count = 0;
 383                desc->pg_base = 0;
 384                desc->pg_recoalesce = 0;
 385
 386                while (!list_empty(&head)) {
 387                        struct nfs_page *req;
 388
 389                        req = list_first_entry(&head, struct nfs_page, wb_list);
 390                        nfs_list_remove_request(req);
 391                        if (__nfs_pageio_add_request(desc, req))
 392                                continue;
 393                        if (desc->pg_error < 0)
 394                                return 0;
 395                        break;
 396                }
 397        } while (desc->pg_recoalesce);
 398        return 1;
 399}
 400
 401int nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
 402                struct nfs_page *req)
 403{
 404        int ret;
 405
 406        do {
 407                ret = __nfs_pageio_add_request(desc, req);
 408                if (ret)
 409                        break;
 410                if (desc->pg_error < 0)
 411                        break;
 412                ret = nfs_do_recoalesce(desc);
 413        } while (ret);
 414        return ret;
 415}
 416EXPORT_SYMBOL_GPL(nfs_pageio_add_request);
 417
 418/**
 419 * nfs_pageio_complete - Complete I/O on an nfs_pageio_descriptor
 420 * @desc: pointer to io descriptor
 421 */
 422void nfs_pageio_complete(struct nfs_pageio_descriptor *desc)
 423{
 424        for (;;) {
 425                nfs_pageio_doio(desc);
 426                if (!desc->pg_recoalesce)
 427                        break;
 428                if (!nfs_do_recoalesce(desc))
 429                        break;
 430        }
 431}
 432EXPORT_SYMBOL_GPL(nfs_pageio_complete);
 433
 434/**
 435 * nfs_pageio_cond_complete - Conditional I/O completion
 436 * @desc: pointer to io descriptor
 437 * @index: page index
 438 *
 439 * It is important to ensure that processes don't try to take locks
 440 * on non-contiguous ranges of pages as that might deadlock. This
 441 * function should be called before attempting to wait on a locked
 442 * nfs_page. It will complete the I/O if the page index 'index'
 443 * is not contiguous with the existing list of pages in 'desc'.
 444 */
 445void nfs_pageio_cond_complete(struct nfs_pageio_descriptor *desc, pgoff_t index)
 446{
 447        if (!list_empty(&desc->pg_list)) {
 448                struct nfs_page *prev = nfs_list_entry(desc->pg_list.prev);
 449                if (index != prev->wb_index + 1)
 450                        nfs_pageio_complete(desc);
 451        }
 452}
 453
 454int __init nfs_init_nfspagecache(void)
 455{
 456        nfs_page_cachep = kmem_cache_create("nfs_page",
 457                                            sizeof(struct nfs_page),
 458                                            0, SLAB_HWCACHE_ALIGN,
 459                                            NULL);
 460        if (nfs_page_cachep == NULL)
 461                return -ENOMEM;
 462
 463        return 0;
 464}
 465
 466void nfs_destroy_nfspagecache(void)
 467{
 468        kmem_cache_destroy(nfs_page_cachep);
 469}
 470
 471
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