bind.c

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/* Bind and unbind a cache from the filesystem backing it
 *
 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells ([email protected])
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public Licence
 * as published by the Free Software Foundation; either version
 * 2 of the Licence, or (at your option) any later version.
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/completion.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/namei.h>
#include <linux/mount.h>
#include <linux/statfs.h>
#include <linux/ctype.h>
#include "internal.h"

static int cachefiles_daemon_add_cache(struct cachefiles_cache *caches);

/*
 * bind a directory as a cache
 */
int cachefiles_daemon_bind(struct cachefiles_cache *cache, char *args)
{
    _enter("{%u,%u,%u,%u,%u,%u},%s",
           cache->frun_percent,
           cache->fcull_percent,
           cache->fstop_percent,
           cache->brun_percent,
           cache->bcull_percent,
           cache->bstop_percent,
           args);

    /* start by checking things over */
    ASSERT(cache->fstop_percent >= 0 &&
           cache->fstop_percent < cache->fcull_percent &&
           cache->fcull_percent < cache->frun_percent &&
           cache->frun_percent  < 100);

    ASSERT(cache->bstop_percent >= 0 &&
           cache->bstop_percent < cache->bcull_percent &&
           cache->bcull_percent < cache->brun_percent &&
           cache->brun_percent  < 100);

    if (*args) {
        kerror("'bind' command doesn't take an argument");
        return -EINVAL;
    }

    if (!cache->rootdirname) {
        kerror("No cache directory specified");
        return -EINVAL;
    }

    /* don't permit already bound caches to be re-bound */
    if (test_bit(CACHEFILES_READY, &cache->flags)) {
        kerror("Cache already bound");
        return -EBUSY;
    }

    /* make sure we have copies of the tag and dirname strings */
    if (!cache->tag) {
        /* the tag string is released by the fops->release()
         * function, so we don't release it on error here */
        cache->tag = kstrdup("CacheFiles", GFP_KERNEL);
        if (!cache->tag)
            return -ENOMEM;
    }

    /* add the cache */
    return cachefiles_daemon_add_cache(cache);
}

/*
 * add a cache
 */
static int cachefiles_daemon_add_cache(struct cachefiles_cache *cache)
{
    struct cachefiles_object *fsdef;
    struct path path;
    struct kstatfs stats;
    struct dentry *graveyard, *cachedir, *root;
    const struct cred *saved_cred;
    int ret;

    _enter("");

    /* we want to work under the module's security ID */
    ret = cachefiles_get_security_ID(cache);
    if (ret < 0)
        return ret;

    cachefiles_begin_secure(cache, &saved_cred);

    /* allocate the root index object */
    ret = -ENOMEM;

    fsdef = kmem_cache_alloc(cachefiles_object_jar, GFP_KERNEL);
    if (!fsdef)
        goto error_root_object;

    ASSERTCMP(fsdef->backer, ==, NULL);

    atomic_set(&fsdef->usage, 1);
    fsdef->type = FSCACHE_COOKIE_TYPE_INDEX;

    _debug("- fsdef %p", fsdef);

    /* look up the directory at the root of the cache */
    ret = kern_path(cache->rootdirname, LOOKUP_DIRECTORY, &path);
    if (ret < 0)
        goto error_open_root;

    cache->mnt = path.mnt;
    root = path.dentry;

    /* check parameters */
    ret = -EOPNOTSUPP;
    if (!root->d_inode ||
        !root->d_inode->i_op ||
        !root->d_inode->i_op->lookup ||
        !root->d_inode->i_op->mkdir ||
        !root->d_inode->i_op->setxattr ||
        !root->d_inode->i_op->getxattr ||
        !root->d_sb->s_op->statfs ||
        !root->d_sb->s_op->sync_fs)
        goto error_unsupported;

    ret = -EROFS;
    if (root->d_sb->s_flags & MS_RDONLY)
        goto error_unsupported;

    /* determine the security of the on-disk cache as this governs
     * security ID of files we create */
    ret = cachefiles_determine_cache_security(cache, root, &saved_cred);
    if (ret < 0)
        goto error_unsupported;

    /* get the cache size and blocksize */
    ret = vfs_statfs(&path, &stats);
    if (ret < 0)
        goto error_unsupported;

    ret = -ERANGE;
    if (stats.f_bsize <= 0)
        goto error_unsupported;

    ret = -EOPNOTSUPP;
    if (stats.f_bsize > PAGE_SIZE)
        goto error_unsupported;

    cache->bsize = stats.f_bsize;
    cache->bshift = 0;
    if (stats.f_bsize < PAGE_SIZE)
        cache->bshift = PAGE_SHIFT - ilog2(stats.f_bsize);

    _debug("blksize %u (shift %u)",
           cache->bsize, cache->bshift);

    _debug("size %llu, avail %llu",
           (unsigned long long) stats.f_blocks,
           (unsigned long long) stats.f_bavail);

    /* set up caching limits */
    do_div(stats.f_files, 100);
    cache->fstop = stats.f_files * cache->fstop_percent;
    cache->fcull = stats.f_files * cache->fcull_percent;
    cache->frun  = stats.f_files * cache->frun_percent;

    _debug("limits {%llu,%llu,%llu} files",
           (unsigned long long) cache->frun,
           (unsigned long long) cache->fcull,
           (unsigned long long) cache->fstop);

    stats.f_blocks >>= cache->bshift;
    do_div(stats.f_blocks, 100);
    cache->bstop = stats.f_blocks * cache->bstop_percent;
    cache->bcull = stats.f_blocks * cache->bcull_percent;
    cache->brun  = stats.f_blocks * cache->brun_percent;

    _debug("limits {%llu,%llu,%llu} blocks",
           (unsigned long long) cache->brun,
           (unsigned long long) cache->bcull,
           (unsigned long long) cache->bstop);

    /* get the cache directory and check its type */
    cachedir = cachefiles_get_directory(cache, root, "cache");
    if (IS_ERR(cachedir)) {
        ret = PTR_ERR(cachedir);
        goto error_unsupported;
    }

    fsdef->dentry = cachedir;
    fsdef->fscache.cookie = NULL;

    ret = cachefiles_check_object_type(fsdef);
    if (ret < 0)
        goto error_unsupported;

    /* get the graveyard directory */
    graveyard = cachefiles_get_directory(cache, root, "graveyard");
    if (IS_ERR(graveyard)) {
        ret = PTR_ERR(graveyard);
        goto error_unsupported;
    }

    cache->graveyard = graveyard;

    /* publish the cache */
    fscache_init_cache(&cache->cache,
               &cachefiles_cache_ops,
               "%s",
               fsdef->dentry->d_sb->s_id);

    fscache_object_init(&fsdef->fscache, NULL, &cache->cache);

    ret = fscache_add_cache(&cache->cache, &fsdef->fscache, cache->tag);
    if (ret < 0)
        goto error_add_cache;

    /* done */
    set_bit(CACHEFILES_READY, &cache->flags);
    dput(root);

    printk(KERN_INFO "CacheFiles:"
           " File cache on %s registered\n",
           cache->cache.identifier);

    /* check how much space the cache has */
    cachefiles_has_space(cache, 0, 0);
    cachefiles_end_secure(cache, saved_cred);
    return 0;

error_add_cache:
    dput(cache->graveyard);
    cache->graveyard = NULL;
error_unsupported:
    mntput(cache->mnt);
    cache->mnt = NULL;
    dput(fsdef->dentry);
    fsdef->dentry = NULL;
    dput(root);
error_open_root:
    kmem_cache_free(cachefiles_object_jar, fsdef);
error_root_object:
    cachefiles_end_secure(cache, saved_cred);
    kerror("Failed to register: %d", ret);
    return ret;
}

/*
 * unbind a cache on fd release
 */
void cachefiles_daemon_unbind(struct cachefiles_cache *cache)
{
    _enter("");

    if (test_bit(CACHEFILES_READY, &cache->flags)) {
        printk(KERN_INFO "CacheFiles:"
               " File cache on %s unregistering\n",
               cache->cache.identifier);

        fscache_withdraw_cache(&cache->cache);
    }

    dput(cache->graveyard);
    mntput(cache->mnt);

    kfree(cache->rootdirname);
    kfree(cache->secctx);
    kfree(cache->tag);

    _leave("");
}