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        struct nfs_lock_context *l_ctx;
 106
 107        /* try to allocate the request struct */
 108        req = nfs_page_alloc();
 109        if (req == NULL)
 110                return ERR_PTR(-ENOMEM);
 111
 112        /* get lock context early so we can deal with alloc failures */
 113        l_ctx = nfs_get_lock_context(ctx);
 114        if (IS_ERR(l_ctx)) {
 115                nfs_page_free(req);
 116                return ERR_CAST(l_ctx);
 117        }
 118        req->wb_lock_context = l_ctx;
 119
 120        /* Initialize the request struct. Initially, we assume a
 121         * long write-back delay. This will be adjusted in
 122         * update_nfs_request below if the region is not locked. */
 123        req->wb_page    = page;
 124        req->wb_index   = page_file_index(page);
 125        page_cache_get(page);
 126        req->wb_offset  = offset;
 127        req->wb_pgbase  = offset;
 128        req->wb_bytes   = count;
 129        req->wb_context = get_nfs_open_context(ctx);
 130        kref_init(&req->wb_kref);
 131        return req;
 132}
 133
 134/**
 135 * nfs_unlock_request - Unlock request and wake up sleepers.
 136 * @req:
 137 */
 138void nfs_unlock_request(struct nfs_page *req)
 139{
 140        if (!NFS_WBACK_BUSY(req)) {
 141                printk(KERN_ERR "NFS: Invalid unlock attempted\n");
 142                BUG();
 143        }
 144        smp_mb__before_clear_bit();
 145        clear_bit(PG_BUSY, &req->wb_flags);
 146        smp_mb__after_clear_bit();
 147        wake_up_bit(&req->wb_flags, PG_BUSY);
 148}
 149
 150/**
 151 * nfs_unlock_and_release_request - Unlock request and release the nfs_page
 152 * @req:
 153 */
 154void nfs_unlock_and_release_request(struct nfs_page *req)
 155{
 156        nfs_unlock_request(req);
 157        nfs_release_request(req);
 158}
 159
 160/*
 161 * nfs_clear_request - Free up all resources allocated to the request
 162 * @req:
 163 *
 164 * Release page and open context resources associated with a read/write
 165 * request after it has completed.
 166 */
 167static void nfs_clear_request(struct nfs_page *req)
 168{
 169        struct page *page = req->wb_page;
 170        struct nfs_open_context *ctx = req->wb_context;
 171        struct nfs_lock_context *l_ctx = req->wb_lock_context;
 172
 173        if (page != NULL) {
 174                page_cache_release(page);
 175                req->wb_page = NULL;
 176        }
 177        if (l_ctx != NULL) {
 178                nfs_put_lock_context(l_ctx);
 179                req->wb_lock_context = NULL;
 180        }
 181        if (ctx != NULL) {
 182                put_nfs_open_context(ctx);
 183                req->wb_context = NULL;
 184        }
 185}
 186
 187
 188/**
 189 * nfs_release_request - Release the count on an NFS read/write request
 190 * @req: request to release
 191 *
 192 * Note: Should never be called with the spinlock held!
 193 */
 194static void nfs_free_request(struct kref *kref)
 195{
 196        struct nfs_page *req = container_of(kref, struct nfs_page, wb_kref);
 197
 198        /* Release struct file and open context */
 199        nfs_clear_request(req);
 200        nfs_page_free(req);
 201}
 202
 203void nfs_release_request(struct nfs_page *req)
 204{
 205        kref_put(&req->wb_kref, nfs_free_request);
 206}
 207
 208static int nfs_wait_bit_uninterruptible(void *word)
 209{
 210        io_schedule();
 211        return 0;
 212}
 213
 214/**
 215 * nfs_wait_on_request - Wait for a request to complete.
 216 * @req: request to wait upon.
 217 *
 218 * Interruptible by fatal signals only.
 219 * The user is responsible for holding a count on the request.
 220 */
 221int
 222nfs_wait_on_request(struct nfs_page *req)
 223{
 224        return wait_on_bit(&req->wb_flags, PG_BUSY,
 225                        nfs_wait_bit_uninterruptible,
 226                        TASK_UNINTERRUPTIBLE);
 227}
 228
 229bool nfs_generic_pg_test(struct nfs_pageio_descriptor *desc, struct nfs_page *prev, struct nfs_page *req)
 230{
 231        /*
 232         * FIXME: ideally we should be able to coalesce all requests
 233         * that are not block boundary aligned, but currently this
 234         * is problematic for the case of bsize < PAGE_CACHE_SIZE,
 235         * since nfs_flush_multi and nfs_pagein_multi assume you
 236         * can have only one struct nfs_page.
 237         */
 238        if (desc->pg_bsize < PAGE_SIZE)
 239                return 0;
 240
 241        return desc->pg_count + req->wb_bytes <= desc->pg_bsize;
 242}
 243EXPORT_SYMBOL_GPL(nfs_generic_pg_test);
 244
 245/**
 246 * nfs_pageio_init - initialise a page io descriptor
 247 * @desc: pointer to descriptor
 248 * @inode: pointer to inode
 249 * @doio: pointer to io function
 250 * @bsize: io block size
 251 * @io_flags: extra parameters for the io function
 252 */
 253void nfs_pageio_init(struct nfs_pageio_descriptor *desc,
 254                     struct inode *inode,
 255                     const struct nfs_pageio_ops *pg_ops,
 256                     const struct nfs_pgio_completion_ops *compl_ops,
 257                     size_t bsize,
 258                     int io_flags)
 259{
 260        INIT_LIST_HEAD(&desc->pg_list);
 261        desc->pg_bytes_written = 0;
 262        desc->pg_count = 0;
 263        desc->pg_bsize = bsize;
 264        desc->pg_base = 0;
 265        desc->pg_moreio = 0;
 266        desc->pg_recoalesce = 0;
 267        desc->pg_inode = inode;
 268        desc->pg_ops = pg_ops;
 269        desc->pg_completion_ops = compl_ops;
 270        desc->pg_ioflags = io_flags;
 271        desc->pg_error = 0;
 272        desc->pg_lseg = NULL;
 273        desc->pg_dreq = NULL;
 274        desc->pg_layout_private = NULL;
 275}
 276EXPORT_SYMBOL_GPL(nfs_pageio_init);
 277
 278/**
 279 * nfs_can_coalesce_requests - test two requests for compatibility
 280 * @prev: pointer to nfs_page
 281 * @req: pointer to nfs_page
 282 *
 283 * The nfs_page structures 'prev' and 'req' are compared to ensure that the
 284 * page data area they describe is contiguous, and that their RPC
 285 * credentials, NFSv4 open state, and lockowners are the same.
 286 *
 287 * Return 'true' if this is the case, else return 'false'.
 288 */
 289static bool nfs_can_coalesce_requests(struct nfs_page *prev,
 290                                      struct nfs_page *req,
 291                                      struct nfs_pageio_descriptor *pgio)
 292{
 293        if (req->wb_context->cred != prev->wb_context->cred)
 294                return false;
 295        if (req->wb_lock_context->lockowner.l_owner != prev->wb_lock_context->lockowner.l_owner)
 296                return false;
 297        if (req->wb_lock_context->lockowner.l_pid != prev->wb_lock_context->lockowner.l_pid)
 298                return false;
 299        if (req->wb_context->state != prev->wb_context->state)
 300                return false;
 301        if (req->wb_pgbase != 0)
 302                return false;
 303        if (prev->wb_pgbase + prev->wb_bytes != PAGE_CACHE_SIZE)
 304                return false;
 305        if (req_offset(req) != req_offset(prev) + prev->wb_bytes)
 306                return false;
 307        return pgio->pg_ops->pg_test(pgio, prev, req);
 308}
 309
 310/**
 311 * nfs_pageio_do_add_request - Attempt to coalesce a request into a page list.
 312 * @desc: destination io descriptor
 313 * @req: request
 314 *
 315 * Returns true if the request 'req' was successfully coalesced into the
 316 * existing list of pages 'desc'.
 317 */
 318static int nfs_pageio_do_add_request(struct nfs_pageio_descriptor *desc,
 319                                     struct nfs_page *req)
 320{
 321        if (desc->pg_count != 0) {
 322                struct nfs_page *prev;
 323
 324                prev = nfs_list_entry(desc->pg_list.prev);
 325                if (!nfs_can_coalesce_requests(prev, req, desc))
 326                        return 0;
 327        } else {
 328                if (desc->pg_ops->pg_init)
 329                        desc->pg_ops->pg_init(desc, req);
 330                desc->pg_base = req->wb_pgbase;
 331        }
 332        nfs_list_remove_request(req);
 333        nfs_list_add_request(req, &desc->pg_list);
 334        desc->pg_count += req->wb_bytes;
 335        return 1;
 336}
 337
 338/*
 339 * Helper for nfs_pageio_add_request and nfs_pageio_complete
 340 */
 341static void nfs_pageio_doio(struct nfs_pageio_descriptor *desc)
 342{
 343        if (!list_empty(&desc->pg_list)) {
 344                int error = desc->pg_ops->pg_doio(desc);
 345                if (error < 0)
 346                        desc->pg_error = error;
 347                else
 348                        desc->pg_bytes_written += desc->pg_count;
 349        }
 350        if (list_empty(&desc->pg_list)) {
 351                desc->pg_count = 0;
 352                desc->pg_base = 0;
 353        }
 354}
 355
 356/**
 357 * nfs_pageio_add_request - Attempt to coalesce a request into a page list.
 358 * @desc: destination io descriptor
 359 * @req: request
 360 *
 361 * Returns true if the request 'req' was successfully coalesced into the
 362 * existing list of pages 'desc'.
 363 */
 364static int __nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
 365                           struct nfs_page *req)
 366{
 367        while (!nfs_pageio_do_add_request(desc, req)) {
 368                desc->pg_moreio = 1;
 369                nfs_pageio_doio(desc);
 370                if (desc->pg_error < 0)
 371                        return 0;
 372                desc->pg_moreio = 0;
 373                if (desc->pg_recoalesce)
 374                        return 0;
 375        }
 376        return 1;
 377}
 378
 379static int nfs_do_recoalesce(struct nfs_pageio_descriptor *desc)
 380{
 381        LIST_HEAD(head);
 382
 383        do {
 384                list_splice_init(&desc->pg_list, &head);
 385                desc->pg_bytes_written -= desc->pg_count;
 386                desc->pg_count = 0;
 387                desc->pg_base = 0;
 388                desc->pg_recoalesce = 0;
 389
 390                while (!list_empty(&head)) {
 391                        struct nfs_page *req;
 392
 393                        req = list_first_entry(&head, struct nfs_page, wb_list);
 394                        nfs_list_remove_request(req);
 395                        if (__nfs_pageio_add_request(desc, req))
 396                                continue;
 397                        if (desc->pg_error < 0)
 398                                return 0;
 399                        break;
 400                }
 401        } while (desc->pg_recoalesce);
 402        return 1;
 403}
 404
 405int nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
 406                struct nfs_page *req)
 407{
 408        int ret;
 409
 410        do {
 411                ret = __nfs_pageio_add_request(desc, req);
 412                if (ret)
 413                        break;
 414                if (desc->pg_error < 0)
 415                        break;
 416                ret = nfs_do_recoalesce(desc);
 417        } while (ret);
 418        return ret;
 419}
 420EXPORT_SYMBOL_GPL(nfs_pageio_add_request);
 421
 422/**
 423 * nfs_pageio_complete - Complete I/O on an nfs_pageio_descriptor
 424 * @desc: pointer to io descriptor
 425 */
 426void nfs_pageio_complete(struct nfs_pageio_descriptor *desc)
 427{
 428        for (;;) {
 429                nfs_pageio_doio(desc);
 430                if (!desc->pg_recoalesce)
 431                        break;
 432                if (!nfs_do_recoalesce(desc))
 433                        break;
 434        }
 435}
 436EXPORT_SYMBOL_GPL(nfs_pageio_complete);
 437
 438/**
 439 * nfs_pageio_cond_complete - Conditional I/O completion
 440 * @desc: pointer to io descriptor
 441 * @index: page index
 442 *
 443 * It is important to ensure that processes don't try to take locks
 444 * on non-contiguous ranges of pages as that might deadlock. This
 445 * function should be called before attempting to wait on a locked
 446 * nfs_page. It will complete the I/O if the page index 'index'
 447 * is not contiguous with the existing list of pages in 'desc'.
 448 */
 449void nfs_pageio_cond_complete(struct nfs_pageio_descriptor *desc, pgoff_t index)
 450{
 451        if (!list_empty(&desc->pg_list)) {
 452                struct nfs_page *prev = nfs_list_entry(desc->pg_list.prev);
 453                if (index != prev->wb_index + 1)
 454                        nfs_pageio_complete(desc);
 455        }
 456}
 457
 458int __init nfs_init_nfspagecache(void)
 459{
 460        nfs_page_cachep = kmem_cache_create("nfs_page",
 461                                            sizeof(struct nfs_page),
 462                                            0, SLAB_HWCACHE_ALIGN,
 463                                            NULL);
 464        if (nfs_page_cachep == NULL)
 465                return -ENOMEM;
 466
 467        return 0;
 468}
 469
 470void nfs_destroy_nfspagecache(void)
 471{
 472        kmem_cache_destroy(nfs_page_cachep);
 473}
 474
 475
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