linux/fs/cachefiles/bind.c
Christian Brauner bf1c82a538 cachefiles: do not yet allow on idmapped mounts
Based on discussions (e.g. in [1]) my understanding of cachefiles and
the cachefiles userspace daemon is that it creates a cache on a local
filesystem (e.g. ext4, xfs etc.) for a network filesystem. The way this
is done is by writing "bind" to /dev/cachefiles and pointing it to the
directory to use as the cache.

Currently this directory can technically also be an idmapped mount but
cachefiles aren't yet fully aware of such mounts and thus don't take the
idmapping into account when creating cache entries. This could leave
users confused as the ownership of the files wouldn't match to what they
expressed in the idmapping. Block cache files on idmapped mounts until
the fscache rework is done and we have ported it to support idmapped
mounts.

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/lkml/20210303161528.n3jzg66ou2wa43qb@wittgenstein [1]
Link: https://lore.kernel.org/r/20210316112257.2974212-1-christian.brauner@ubuntu.com/ # v1
Link: https://listman.redhat.com/archives/linux-cachefs/2021-March/msg00044.html # v2
Link: https://lore.kernel.org/r/20210319114146.410329-1-christian.brauner@ubuntu.com/ # v3
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-03-24 10:20:22 -07:00

281 lines
6.9 KiB
C

// SPDX-License-Identifier: GPL-2.0-or-later
/* Bind and unbind a cache from the filesystem backing it
*
* Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*/
#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 <linux/xattr.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) {
pr_err("'bind' command doesn't take an argument\n");
return -EINVAL;
}
if (!cache->rootdirname) {
pr_err("No cache directory specified\n");
return -EINVAL;
}
/* don't permit already bound caches to be re-bound */
if (test_bit(CACHEFILES_READY, &cache->flags)) {
pr_err("Cache already bound\n");
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;
ret = -EINVAL;
if (mnt_user_ns(path.mnt) != &init_user_ns) {
pr_warn("File cache on idmapped mounts not supported");
goto error_unsupported;
}
/* check parameters */
ret = -EOPNOTSUPP;
if (d_is_negative(root) ||
!d_backing_inode(root)->i_op->lookup ||
!d_backing_inode(root)->i_op->mkdir ||
!(d_backing_inode(root)->i_opflags & IOP_XATTR) ||
!root->d_sb->s_op->statfs ||
!root->d_sb->s_op->sync_fs)
goto error_unsupported;
ret = -EROFS;
if (sb_rdonly(root->d_sb))
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, &fscache_fsdef_index,
&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);
pr_info("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);
pr_err("Failed to register: %d\n", 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)) {
pr_info("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("");
}