cache.c

Go to the documentation of this file.

/*
 * V9FS cache definitions.
 *
 *  Copyright (C) 2009 by Abhishek Kulkarni <[email protected]>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2
 *  as published by the Free Software Foundation.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to:
 *  Free Software Foundation
 *  51 Franklin Street, Fifth Floor
 *  Boston, MA  02111-1301  USA
 *
 */

#include <linux/jiffies.h>
#include <linux/file.h>
#include <linux/slab.h>
#include <linux/stat.h>
#include <linux/sched.h>
#include <linux/fs.h>
#include <net/9p/9p.h>

#include "v9fs.h"
#include "cache.h"

#define CACHETAG_LEN  11

struct fscache_netfs v9fs_cache_netfs = {
    .name       = "9p",
    .version    = 0,
};

static
int v9fs_random_cachetag(struct v9fs_session_info *v9ses)
{
    v9ses->cachetag = kmalloc(CACHETAG_LEN, GFP_KERNEL);
    if (!v9ses->cachetag)
        return -ENOMEM;

    return scnprintf(v9ses->cachetag, CACHETAG_LEN, "%lu", jiffies);
}

static uint16_t v9fs_cache_session_get_key(const void *cookie_netfs_data,
                       void *buffer, uint16_t bufmax)
{
    struct v9fs_session_info *v9ses;
    uint16_t klen = 0;

    v9ses = (struct v9fs_session_info *)cookie_netfs_data;
    p9_debug(P9_DEBUG_FSC, "session %p buf %p size %u\n",
         v9ses, buffer, bufmax);

    if (v9ses->cachetag)
        klen = strlen(v9ses->cachetag);

    if (klen > bufmax)
        return 0;

    memcpy(buffer, v9ses->cachetag, klen);
    p9_debug(P9_DEBUG_FSC, "cache session tag %s\n", v9ses->cachetag);
    return klen;
}

const struct fscache_cookie_def v9fs_cache_session_index_def = {
    .name       = "9P.session",
    .type       = FSCACHE_COOKIE_TYPE_INDEX,
    .get_key    = v9fs_cache_session_get_key,
};

void v9fs_cache_session_get_cookie(struct v9fs_session_info *v9ses)
{
    /* If no cache session tag was specified, we generate a random one. */
    if (!v9ses->cachetag)
        v9fs_random_cachetag(v9ses);

    v9ses->fscache = fscache_acquire_cookie(v9fs_cache_netfs.primary_index,
                        &v9fs_cache_session_index_def,
                        v9ses);
    p9_debug(P9_DEBUG_FSC, "session %p get cookie %p\n",
         v9ses, v9ses->fscache);
}

void v9fs_cache_session_put_cookie(struct v9fs_session_info *v9ses)
{
    p9_debug(P9_DEBUG_FSC, "session %p put cookie %p\n",
         v9ses, v9ses->fscache);
    fscache_relinquish_cookie(v9ses->fscache, 0);
    v9ses->fscache = NULL;
}


static uint16_t v9fs_cache_inode_get_key(const void *cookie_netfs_data,
                     void *buffer, uint16_t bufmax)
{
    const struct v9fs_inode *v9inode = cookie_netfs_data;
    memcpy(buffer, &v9inode->qid.path, sizeof(v9inode->qid.path));
    p9_debug(P9_DEBUG_FSC, "inode %p get key %llu\n",
         &v9inode->vfs_inode, v9inode->qid.path);
    return sizeof(v9inode->qid.path);
}

static void v9fs_cache_inode_get_attr(const void *cookie_netfs_data,
                      uint64_t *size)
{
    const struct v9fs_inode *v9inode = cookie_netfs_data;
    *size = i_size_read(&v9inode->vfs_inode);

    p9_debug(P9_DEBUG_FSC, "inode %p get attr %llu\n",
         &v9inode->vfs_inode, *size);
}

static uint16_t v9fs_cache_inode_get_aux(const void *cookie_netfs_data,
                     void *buffer, uint16_t buflen)
{
    const struct v9fs_inode *v9inode = cookie_netfs_data;
    memcpy(buffer, &v9inode->qid.version, sizeof(v9inode->qid.version));
    p9_debug(P9_DEBUG_FSC, "inode %p get aux %u\n",
         &v9inode->vfs_inode, v9inode->qid.version);
    return sizeof(v9inode->qid.version);
}

static enum
fscache_checkaux v9fs_cache_inode_check_aux(void *cookie_netfs_data,
                        const void *buffer,
                        uint16_t buflen)
{
    const struct v9fs_inode *v9inode = cookie_netfs_data;

    if (buflen != sizeof(v9inode->qid.version))
        return FSCACHE_CHECKAUX_OBSOLETE;

    if (memcmp(buffer, &v9inode->qid.version,
           sizeof(v9inode->qid.version)))
        return FSCACHE_CHECKAUX_OBSOLETE;

    return FSCACHE_CHECKAUX_OKAY;
}

static void v9fs_cache_inode_now_uncached(void *cookie_netfs_data)
{
    struct v9fs_inode *v9inode = cookie_netfs_data;
    struct pagevec pvec;
    pgoff_t first;
    int loop, nr_pages;

    pagevec_init(&pvec, 0);
    first = 0;

    for (;;) {
        nr_pages = pagevec_lookup(&pvec, v9inode->vfs_inode.i_mapping,
                      first,
                      PAGEVEC_SIZE - pagevec_count(&pvec));
        if (!nr_pages)
            break;

        for (loop = 0; loop < nr_pages; loop++)
            ClearPageFsCache(pvec.pages[loop]);

        first = pvec.pages[nr_pages - 1]->index + 1;

        pvec.nr = nr_pages;
        pagevec_release(&pvec);
        cond_resched();
    }
}

const struct fscache_cookie_def v9fs_cache_inode_index_def = {
    .name       = "9p.inode",
    .type       = FSCACHE_COOKIE_TYPE_DATAFILE,
    .get_key    = v9fs_cache_inode_get_key,
    .get_attr   = v9fs_cache_inode_get_attr,
    .get_aux    = v9fs_cache_inode_get_aux,
    .check_aux  = v9fs_cache_inode_check_aux,
    .now_uncached   = v9fs_cache_inode_now_uncached,
};

void v9fs_cache_inode_get_cookie(struct inode *inode)
{
    struct v9fs_inode *v9inode;
    struct v9fs_session_info *v9ses;

    if (!S_ISREG(inode->i_mode))
        return;

    v9inode = V9FS_I(inode);
    if (v9inode->fscache)
        return;

    v9ses = v9fs_inode2v9ses(inode);
    v9inode->fscache = fscache_acquire_cookie(v9ses->fscache,
                          &v9fs_cache_inode_index_def,
                          v9inode);

    p9_debug(P9_DEBUG_FSC, "inode %p get cookie %p\n",
         inode, v9inode->fscache);
}

void v9fs_cache_inode_put_cookie(struct inode *inode)
{
    struct v9fs_inode *v9inode = V9FS_I(inode);

    if (!v9inode->fscache)
        return;
    p9_debug(P9_DEBUG_FSC, "inode %p put cookie %p\n",
         inode, v9inode->fscache);

    fscache_relinquish_cookie(v9inode->fscache, 0);
    v9inode->fscache = NULL;
}

void v9fs_cache_inode_flush_cookie(struct inode *inode)
{
    struct v9fs_inode *v9inode = V9FS_I(inode);

    if (!v9inode->fscache)
        return;
    p9_debug(P9_DEBUG_FSC, "inode %p flush cookie %p\n",
         inode, v9inode->fscache);

    fscache_relinquish_cookie(v9inode->fscache, 1);
    v9inode->fscache = NULL;
}

void v9fs_cache_inode_set_cookie(struct inode *inode, struct file *filp)
{
    struct v9fs_inode *v9inode = V9FS_I(inode);
    struct p9_fid *fid;

    if (!v9inode->fscache)
        return;

    spin_lock(&v9inode->fscache_lock);
    fid = filp->private_data;
    if ((filp->f_flags & O_ACCMODE) != O_RDONLY)
        v9fs_cache_inode_flush_cookie(inode);
    else
        v9fs_cache_inode_get_cookie(inode);

    spin_unlock(&v9inode->fscache_lock);
}

void v9fs_cache_inode_reset_cookie(struct inode *inode)
{
    struct v9fs_inode *v9inode = V9FS_I(inode);
    struct v9fs_session_info *v9ses;
    struct fscache_cookie *old;

    if (!v9inode->fscache)
        return;

    old = v9inode->fscache;

    spin_lock(&v9inode->fscache_lock);
    fscache_relinquish_cookie(v9inode->fscache, 1);

    v9ses = v9fs_inode2v9ses(inode);
    v9inode->fscache = fscache_acquire_cookie(v9ses->fscache,
                          &v9fs_cache_inode_index_def,
                          v9inode);
    p9_debug(P9_DEBUG_FSC, "inode %p revalidating cookie old %p new %p\n",
         inode, old, v9inode->fscache);

    spin_unlock(&v9inode->fscache_lock);
}

int __v9fs_fscache_release_page(struct page *page, gfp_t gfp)
{
    struct inode *inode = page->mapping->host;
    struct v9fs_inode *v9inode = V9FS_I(inode);

    BUG_ON(!v9inode->fscache);

    return fscache_maybe_release_page(v9inode->fscache, page, gfp);
}

void __v9fs_fscache_invalidate_page(struct page *page)
{
    struct inode *inode = page->mapping->host;
    struct v9fs_inode *v9inode = V9FS_I(inode);

    BUG_ON(!v9inode->fscache);

    if (PageFsCache(page)) {
        fscache_wait_on_page_write(v9inode->fscache, page);
        BUG_ON(!PageLocked(page));
        fscache_uncache_page(v9inode->fscache, page);
    }
}

static void v9fs_vfs_readpage_complete(struct page *page, void *data,
                       int error)
{
    if (!error)
        SetPageUptodate(page);

    unlock_page(page);
}

int __v9fs_readpage_from_fscache(struct inode *inode, struct page *page)
{
    int ret;
    const struct v9fs_inode *v9inode = V9FS_I(inode);

    p9_debug(P9_DEBUG_FSC, "inode %p page %p\n", inode, page);
    if (!v9inode->fscache)
        return -ENOBUFS;

    ret = fscache_read_or_alloc_page(v9inode->fscache,
                     page,
                     v9fs_vfs_readpage_complete,
                     NULL,
                     GFP_KERNEL);
    switch (ret) {
    case -ENOBUFS:
    case -ENODATA:
        p9_debug(P9_DEBUG_FSC, "page/inode not in cache %d\n", ret);
        return 1;
    case 0:
        p9_debug(P9_DEBUG_FSC, "BIO submitted\n");
        return ret;
    default:
        p9_debug(P9_DEBUG_FSC, "ret %d\n", ret);
        return ret;
    }
}

int __v9fs_readpages_from_fscache(struct inode *inode,
                  struct address_space *mapping,
                  struct list_head *pages,
                  unsigned *nr_pages)
{
    int ret;
    const struct v9fs_inode *v9inode = V9FS_I(inode);

    p9_debug(P9_DEBUG_FSC, "inode %p pages %u\n", inode, *nr_pages);
    if (!v9inode->fscache)
        return -ENOBUFS;

    ret = fscache_read_or_alloc_pages(v9inode->fscache,
                      mapping, pages, nr_pages,
                      v9fs_vfs_readpage_complete,
                      NULL,
                      mapping_gfp_mask(mapping));
    switch (ret) {
    case -ENOBUFS:
    case -ENODATA:
        p9_debug(P9_DEBUG_FSC, "pages/inodes not in cache %d\n", ret);
        return 1;
    case 0:
        BUG_ON(!list_empty(pages));
        BUG_ON(*nr_pages != 0);
        p9_debug(P9_DEBUG_FSC, "BIO submitted\n");
        return ret;
    default:
        p9_debug(P9_DEBUG_FSC, "ret %d\n", ret);
        return ret;
    }
}

void __v9fs_readpage_to_fscache(struct inode *inode, struct page *page)
{
    int ret;
    const struct v9fs_inode *v9inode = V9FS_I(inode);

    p9_debug(P9_DEBUG_FSC, "inode %p page %p\n", inode, page);
    ret = fscache_write_page(v9inode->fscache, page, GFP_KERNEL);
    p9_debug(P9_DEBUG_FSC, "ret =  %d\n", ret);
    if (ret != 0)
        v9fs_uncache_page(inode, page);
}

/*
 * wait for a page to complete writing to the cache
 */
void __v9fs_fscache_wait_on_page_write(struct inode *inode, struct page *page)
{
    const struct v9fs_inode *v9inode = V9FS_I(inode);
    p9_debug(P9_DEBUG_FSC, "inode %p page %p\n", inode, page);
    if (PageFsCache(page))
        fscache_wait_on_page_write(v9inode->fscache, page);
}