linux/fs/9p/cache.c
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   1/*
   2 * V9FS cache definitions.
   3 *
   4 *  Copyright (C) 2009 by Abhishek Kulkarni <adkulkar@umail.iu.edu>
   5 *
   6 *  This program is free software; you can redistribute it and/or modify
   7 *  it under the terms of the GNU General Public License version 2
   8 *  as published by the Free Software Foundation.
   9 *
  10 *  This program is distributed in the hope that it will be useful,
  11 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 *  GNU General Public License for more details.
  14 *
  15 *  You should have received a copy of the GNU General Public License
  16 *  along with this program; if not, write to:
  17 *  Free Software Foundation
  18 *  51 Franklin Street, Fifth Floor
  19 *  Boston, MA  02111-1301  USA
  20 *
  21 */
  22
  23#include <linux/jiffies.h>
  24#include <linux/file.h>
  25#include <linux/slab.h>
  26#include <linux/stat.h>
  27#include <linux/sched.h>
  28#include <linux/fs.h>
  29#include <net/9p/9p.h>
  30
  31#include "v9fs.h"
  32#include "cache.h"
  33
  34#define CACHETAG_LEN  11
  35
  36struct fscache_netfs v9fs_cache_netfs = {
  37        .name           = "9p",
  38        .version        = 0,
  39};
  40
  41/**
  42 * v9fs_random_cachetag - Generate a random tag to be associated
  43 *                        with a new cache session.
  44 *
  45 * The value of jiffies is used for a fairly randomly cache tag.
  46 */
  47
  48static
  49int v9fs_random_cachetag(struct v9fs_session_info *v9ses)
  50{
  51        v9ses->cachetag = kmalloc(CACHETAG_LEN, GFP_KERNEL);
  52        if (!v9ses->cachetag)
  53                return -ENOMEM;
  54
  55        return scnprintf(v9ses->cachetag, CACHETAG_LEN, "%lu", jiffies);
  56}
  57
  58static uint16_t v9fs_cache_session_get_key(const void *cookie_netfs_data,
  59                                           void *buffer, uint16_t bufmax)
  60{
  61        struct v9fs_session_info *v9ses;
  62        uint16_t klen = 0;
  63
  64        v9ses = (struct v9fs_session_info *)cookie_netfs_data;
  65        p9_debug(P9_DEBUG_FSC, "session %p buf %p size %u\n",
  66                 v9ses, buffer, bufmax);
  67
  68        if (v9ses->cachetag)
  69                klen = strlen(v9ses->cachetag);
  70
  71        if (klen > bufmax)
  72                return 0;
  73
  74        memcpy(buffer, v9ses->cachetag, klen);
  75        p9_debug(P9_DEBUG_FSC, "cache session tag %s\n", v9ses->cachetag);
  76        return klen;
  77}
  78
  79const struct fscache_cookie_def v9fs_cache_session_index_def = {
  80        .name           = "9P.session",
  81        .type           = FSCACHE_COOKIE_TYPE_INDEX,
  82        .get_key        = v9fs_cache_session_get_key,
  83};
  84
  85void v9fs_cache_session_get_cookie(struct v9fs_session_info *v9ses)
  86{
  87        /* If no cache session tag was specified, we generate a random one. */
  88        if (!v9ses->cachetag)
  89                v9fs_random_cachetag(v9ses);
  90
  91        v9ses->fscache = fscache_acquire_cookie(v9fs_cache_netfs.primary_index,
  92                                                &v9fs_cache_session_index_def,
  93                                                v9ses);
  94        p9_debug(P9_DEBUG_FSC, "session %p get cookie %p\n",
  95                 v9ses, v9ses->fscache);
  96}
  97
  98void v9fs_cache_session_put_cookie(struct v9fs_session_info *v9ses)
  99{
 100        p9_debug(P9_DEBUG_FSC, "session %p put cookie %p\n",
 101                 v9ses, v9ses->fscache);
 102        fscache_relinquish_cookie(v9ses->fscache, 0);
 103        v9ses->fscache = NULL;
 104}
 105
 106
 107static uint16_t v9fs_cache_inode_get_key(const void *cookie_netfs_data,
 108                                         void *buffer, uint16_t bufmax)
 109{
 110        const struct v9fs_inode *v9inode = cookie_netfs_data;
 111        memcpy(buffer, &v9inode->qid.path, sizeof(v9inode->qid.path));
 112        p9_debug(P9_DEBUG_FSC, "inode %p get key %llu\n",
 113                 &v9inode->vfs_inode, v9inode->qid.path);
 114        return sizeof(v9inode->qid.path);
 115}
 116
 117static void v9fs_cache_inode_get_attr(const void *cookie_netfs_data,
 118                                      uint64_t *size)
 119{
 120        const struct v9fs_inode *v9inode = cookie_netfs_data;
 121        *size = i_size_read(&v9inode->vfs_inode);
 122
 123        p9_debug(P9_DEBUG_FSC, "inode %p get attr %llu\n",
 124                 &v9inode->vfs_inode, *size);
 125}
 126
 127static uint16_t v9fs_cache_inode_get_aux(const void *cookie_netfs_data,
 128                                         void *buffer, uint16_t buflen)
 129{
 130        const struct v9fs_inode *v9inode = cookie_netfs_data;
 131        memcpy(buffer, &v9inode->qid.version, sizeof(v9inode->qid.version));
 132        p9_debug(P9_DEBUG_FSC, "inode %p get aux %u\n",
 133                 &v9inode->vfs_inode, v9inode->qid.version);
 134        return sizeof(v9inode->qid.version);
 135}
 136
 137static enum
 138fscache_checkaux v9fs_cache_inode_check_aux(void *cookie_netfs_data,
 139                                            const void *buffer,
 140                                            uint16_t buflen)
 141{
 142        const struct v9fs_inode *v9inode = cookie_netfs_data;
 143
 144        if (buflen != sizeof(v9inode->qid.version))
 145                return FSCACHE_CHECKAUX_OBSOLETE;
 146
 147        if (memcmp(buffer, &v9inode->qid.version,
 148                   sizeof(v9inode->qid.version)))
 149                return FSCACHE_CHECKAUX_OBSOLETE;
 150
 151        return FSCACHE_CHECKAUX_OKAY;
 152}
 153
 154static void v9fs_cache_inode_now_uncached(void *cookie_netfs_data)
 155{
 156        struct v9fs_inode *v9inode = cookie_netfs_data;
 157        struct pagevec pvec;
 158        pgoff_t first;
 159        int loop, nr_pages;
 160
 161        pagevec_init(&pvec, 0);
 162        first = 0;
 163
 164        for (;;) {
 165                nr_pages = pagevec_lookup(&pvec, v9inode->vfs_inode.i_mapping,
 166                                          first,
 167                                          PAGEVEC_SIZE - pagevec_count(&pvec));
 168                if (!nr_pages)
 169                        break;
 170
 171                for (loop = 0; loop < nr_pages; loop++)
 172                        ClearPageFsCache(pvec.pages[loop]);
 173
 174                first = pvec.pages[nr_pages - 1]->index + 1;
 175
 176                pvec.nr = nr_pages;
 177                pagevec_release(&pvec);
 178                cond_resched();
 179        }
 180}
 181
 182const struct fscache_cookie_def v9fs_cache_inode_index_def = {
 183        .name           = "9p.inode",
 184        .type           = FSCACHE_COOKIE_TYPE_DATAFILE,
 185        .get_key        = v9fs_cache_inode_get_key,
 186        .get_attr       = v9fs_cache_inode_get_attr,
 187        .get_aux        = v9fs_cache_inode_get_aux,
 188        .check_aux      = v9fs_cache_inode_check_aux,
 189        .now_uncached   = v9fs_cache_inode_now_uncached,
 190};
 191
 192void v9fs_cache_inode_get_cookie(struct inode *inode)
 193{
 194        struct v9fs_inode *v9inode;
 195        struct v9fs_session_info *v9ses;
 196
 197        if (!S_ISREG(inode->i_mode))
 198                return;
 199
 200        v9inode = V9FS_I(inode);
 201        if (v9inode->fscache)
 202                return;
 203
 204        v9ses = v9fs_inode2v9ses(inode);
 205        v9inode->fscache = fscache_acquire_cookie(v9ses->fscache,
 206                                                  &v9fs_cache_inode_index_def,
 207                                                  v9inode);
 208
 209        p9_debug(P9_DEBUG_FSC, "inode %p get cookie %p\n",
 210                 inode, v9inode->fscache);
 211}
 212
 213void v9fs_cache_inode_put_cookie(struct inode *inode)
 214{
 215        struct v9fs_inode *v9inode = V9FS_I(inode);
 216
 217        if (!v9inode->fscache)
 218                return;
 219        p9_debug(P9_DEBUG_FSC, "inode %p put cookie %p\n",
 220                 inode, v9inode->fscache);
 221
 222        fscache_relinquish_cookie(v9inode->fscache, 0);
 223        v9inode->fscache = NULL;
 224}
 225
 226void v9fs_cache_inode_flush_cookie(struct inode *inode)
 227{
 228        struct v9fs_inode *v9inode = V9FS_I(inode);
 229
 230        if (!v9inode->fscache)
 231                return;
 232        p9_debug(P9_DEBUG_FSC, "inode %p flush cookie %p\n",
 233                 inode, v9inode->fscache);
 234
 235        fscache_relinquish_cookie(v9inode->fscache, 1);
 236        v9inode->fscache = NULL;
 237}
 238
 239void v9fs_cache_inode_set_cookie(struct inode *inode, struct file *filp)
 240{
 241        struct v9fs_inode *v9inode = V9FS_I(inode);
 242        struct p9_fid *fid;
 243
 244        if (!v9inode->fscache)
 245                return;
 246
 247        spin_lock(&v9inode->fscache_lock);
 248        fid = filp->private_data;
 249        if ((filp->f_flags & O_ACCMODE) != O_RDONLY)
 250                v9fs_cache_inode_flush_cookie(inode);
 251        else
 252                v9fs_cache_inode_get_cookie(inode);
 253
 254        spin_unlock(&v9inode->fscache_lock);
 255}
 256
 257void v9fs_cache_inode_reset_cookie(struct inode *inode)
 258{
 259        struct v9fs_inode *v9inode = V9FS_I(inode);
 260        struct v9fs_session_info *v9ses;
 261        struct fscache_cookie *old;
 262
 263        if (!v9inode->fscache)
 264                return;
 265
 266        old = v9inode->fscache;
 267
 268        spin_lock(&v9inode->fscache_lock);
 269        fscache_relinquish_cookie(v9inode->fscache, 1);
 270
 271        v9ses = v9fs_inode2v9ses(inode);
 272        v9inode->fscache = fscache_acquire_cookie(v9ses->fscache,
 273                                                  &v9fs_cache_inode_index_def,
 274                                                  v9inode);
 275        p9_debug(P9_DEBUG_FSC, "inode %p revalidating cookie old %p new %p\n",
 276                 inode, old, v9inode->fscache);
 277
 278        spin_unlock(&v9inode->fscache_lock);
 279}
 280
 281int __v9fs_fscache_release_page(struct page *page, gfp_t gfp)
 282{
 283        struct inode *inode = page->mapping->host;
 284        struct v9fs_inode *v9inode = V9FS_I(inode);
 285
 286        BUG_ON(!v9inode->fscache);
 287
 288        return fscache_maybe_release_page(v9inode->fscache, page, gfp);
 289}
 290
 291void __v9fs_fscache_invalidate_page(struct page *page)
 292{
 293        struct inode *inode = page->mapping->host;
 294        struct v9fs_inode *v9inode = V9FS_I(inode);
 295
 296        BUG_ON(!v9inode->fscache);
 297
 298        if (PageFsCache(page)) {
 299                fscache_wait_on_page_write(v9inode->fscache, page);
 300                BUG_ON(!PageLocked(page));
 301                fscache_uncache_page(v9inode->fscache, page);
 302        }
 303}
 304
 305static void v9fs_vfs_readpage_complete(struct page *page, void *data,
 306                                       int error)
 307{
 308        if (!error)
 309                SetPageUptodate(page);
 310
 311        unlock_page(page);
 312}
 313
 314/**
 315 * __v9fs_readpage_from_fscache - read a page from cache
 316 *
 317 * Returns 0 if the pages are in cache and a BIO is submitted,
 318 * 1 if the pages are not in cache and -error otherwise.
 319 */
 320
 321int __v9fs_readpage_from_fscache(struct inode *inode, struct page *page)
 322{
 323        int ret;
 324        const struct v9fs_inode *v9inode = V9FS_I(inode);
 325
 326        p9_debug(P9_DEBUG_FSC, "inode %p page %p\n", inode, page);
 327        if (!v9inode->fscache)
 328                return -ENOBUFS;
 329
 330        ret = fscache_read_or_alloc_page(v9inode->fscache,
 331                                         page,
 332                                         v9fs_vfs_readpage_complete,
 333                                         NULL,
 334                                         GFP_KERNEL);
 335        switch (ret) {
 336        case -ENOBUFS:
 337        case -ENODATA:
 338                p9_debug(P9_DEBUG_FSC, "page/inode not in cache %d\n", ret);
 339                return 1;
 340        case 0:
 341                p9_debug(P9_DEBUG_FSC, "BIO submitted\n");
 342                return ret;
 343        default:
 344                p9_debug(P9_DEBUG_FSC, "ret %d\n", ret);
 345                return ret;
 346        }
 347}
 348
 349/**
 350 * __v9fs_readpages_from_fscache - read multiple pages from cache
 351 *
 352 * Returns 0 if the pages are in cache and a BIO is submitted,
 353 * 1 if the pages are not in cache and -error otherwise.
 354 */
 355
 356int __v9fs_readpages_from_fscache(struct inode *inode,
 357                                  struct address_space *mapping,
 358                                  struct list_head *pages,
 359                                  unsigned *nr_pages)
 360{
 361        int ret;
 362        const struct v9fs_inode *v9inode = V9FS_I(inode);
 363
 364        p9_debug(P9_DEBUG_FSC, "inode %p pages %u\n", inode, *nr_pages);
 365        if (!v9inode->fscache)
 366                return -ENOBUFS;
 367
 368        ret = fscache_read_or_alloc_pages(v9inode->fscache,
 369                                          mapping, pages, nr_pages,
 370                                          v9fs_vfs_readpage_complete,
 371                                          NULL,
 372                                          mapping_gfp_mask(mapping));
 373        switch (ret) {
 374        case -ENOBUFS:
 375        case -ENODATA:
 376                p9_debug(P9_DEBUG_FSC, "pages/inodes not in cache %d\n", ret);
 377                return 1;
 378        case 0:
 379                BUG_ON(!list_empty(pages));
 380                BUG_ON(*nr_pages != 0);
 381                p9_debug(P9_DEBUG_FSC, "BIO submitted\n");
 382                return ret;
 383        default:
 384                p9_debug(P9_DEBUG_FSC, "ret %d\n", ret);
 385                return ret;
 386        }
 387}
 388
 389/**
 390 * __v9fs_readpage_to_fscache - write a page to the cache
 391 *
 392 */
 393
 394void __v9fs_readpage_to_fscache(struct inode *inode, struct page *page)
 395{
 396        int ret;
 397        const struct v9fs_inode *v9inode = V9FS_I(inode);
 398
 399        p9_debug(P9_DEBUG_FSC, "inode %p page %p\n", inode, page);
 400        ret = fscache_write_page(v9inode->fscache, page, GFP_KERNEL);
 401        p9_debug(P9_DEBUG_FSC, "ret =  %d\n", ret);
 402        if (ret != 0)
 403                v9fs_uncache_page(inode, page);
 404}
 405
 406/*
 407 * wait for a page to complete writing to the cache
 408 */
 409void __v9fs_fscache_wait_on_page_write(struct inode *inode, struct page *page)
 410{
 411        const struct v9fs_inode *v9inode = V9FS_I(inode);
 412        p9_debug(P9_DEBUG_FSC, "inode %p page %p\n", inode, page);
 413        if (PageFsCache(page))
 414                fscache_wait_on_page_write(v9inode->fscache, page);
 415}
 416
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