// SPDX-License-Identifier: GPL-2.0-or-later
/* Manage high-level VFS aspects of a cache.
*
* Copyright (C) 2007, 2021 Red Hat, Inc. All Rights Reserved.
* Written by David Howells ([email protected])
*/
#include <linux/slab.h>
#include <linux/statfs.h>
#include <linux/namei.h>
#include <trace/events/fscache.h>
#include "internal.h"
/*
* Bring a cache online.
*/
int cachefiles_add_cache(struct cachefiles_cache *cache)
{
struct fscache_cache *cache_cookie;
struct path path;
struct kstatfs stats;
struct dentry *graveyard, *cachedir, *root;
const struct cred *saved_cred;
int ret;
_enter("");
cache_cookie = fscache_acquire_cache(cache->tag);
if (IS_ERR(cache_cookie))
return PTR_ERR(cache_cookie);
/* we want to work under the module's security ID */
ret = cachefiles_get_security_ID(cache);
if (ret < 0)
goto error_getsec;
cachefiles_begin_secure(cache, &saved_cred);
/* 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 (is_idmapped_mnt(path.mnt)) {
pr_warn("File cache on idmapped mounts not supported");
goto error_unsupported;
}
/* Check features of the backing filesystem:
* - Directories must support looking up and directory creation
* - We create tmpfiles to handle invalidation
* - We use xattrs to store metadata
* - We need to be able to query the amount of space available
* - We want to be able to sync the filesystem when stopping the cache
* - We use DIO to/from pages, so the blocksize mustn't be too big.
*/
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_op->tmpfile ||
!(d_backing_inode(root)->i_opflags & IOP_XATTR) ||
!root->d_sb->s_op->statfs ||
!root->d_sb->s_op->sync_fs ||
root->d_sb->s_blocksize > PAGE_SIZE)
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 = 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);
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", NULL);
if (IS_ERR(cachedir)) {
ret = PTR_ERR(cachedir);
goto error_unsupported;
}
cache->store = cachedir;
/* get the graveyard directory */
graveyard = cachefiles_get_directory(cache, root, "graveyard", NULL);
if (IS_ERR(graveyard)) {
ret = PTR_ERR(graveyard);
goto error_unsupported;
}
cache->graveyard = graveyard;
cache->cache = cache_cookie;
ret = fscache_add_cache(cache_cookie, &cachefiles_cache_ops, cache);
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_cookie->name);
/* check how much space the cache has */
cachefiles_has_space(cache, 0, 0, cachefiles_has_space_check);
cachefiles_end_secure(cache, saved_cred);
_leave(" = 0 [%px]", cache->cache);
return 0;
error_add_cache:
cachefiles_put_directory(cache->graveyard);
cache->graveyard = NULL;
error_unsupported:
cachefiles_put_directory(cache->store);
cache->store = NULL;
mntput(cache->mnt);
cache->mnt = NULL;
dput(root);
error_open_root:
cachefiles_end_secure(cache, saved_cred);
put_cred(cache->cache_cred);
cache->cache_cred = NULL;
error_getsec:
fscache_relinquish_cache(cache_cookie);
cache->cache = NULL;
pr_err("Failed to register: %d\n", ret);
return ret;
}
/*
* See if we have space for a number of pages and/or a number of files in the
* cache
*/
int cachefiles_has_space(struct cachefiles_cache *cache,
unsigned fnr, unsigned bnr,
enum cachefiles_has_space_for reason)
{
struct kstatfs stats;
u64 b_avail, b_writing;
int ret;
struct path path = {
.mnt = cache->mnt,
.dentry = cache->mnt->mnt_root,
};
//_enter("{%llu,%llu,%llu,%llu,%llu,%llu},%u,%u",
// (unsigned long long) cache->frun,
// (unsigned long long) cache->fcull,
// (unsigned long long) cache->fstop,
// (unsigned long long) cache->brun,
// (unsigned long long) cache->bcull,
// (unsigned long long) cache->bstop,
// fnr, bnr);
/* find out how many pages of blockdev are available */
memset(&stats, 0, sizeof(stats));
ret = vfs_statfs(&path, &stats);
if (ret < 0) {
trace_cachefiles_vfs_error(NULL, d_inode(path.dentry), ret,
cachefiles_trace_statfs_error);
if (ret == -EIO)
cachefiles_io_error(cache, "statfs failed");
_leave(" = %d", ret);
return ret;
}
b_avail = stats.f_bavail;
b_writing = atomic_long_read(&cache->b_writing);
if (b_avail > b_writing)
b_avail -= b_writing;
else
b_avail = 0;
//_debug("avail %llu,%llu",
// (unsigned long long)stats.f_ffree,
// (unsigned long long)b_avail);
/* see if there is sufficient space */
if (stats.f_ffree > fnr)
stats.f_ffree -= fnr;
else
stats.f_ffree = 0;
if (b_avail > bnr)
b_avail -= bnr;
else
b_avail = 0;
ret = -ENOBUFS;
if (stats.f_ffree < cache->fstop ||
b_avail < cache->bstop)
goto stop_and_begin_cull;
ret = 0;
if (stats.f_ffree < cache->fcull ||
b_avail < cache->bcull)
goto begin_cull;
if (test_bit(CACHEFILES_CULLING, &cache->flags) &&
stats.f_ffree >= cache->frun &&
b_avail >= cache->brun &&
test_and_clear_bit(CACHEFILES_CULLING, &cache->flags)
) {
_debug("cease culling");
cachefiles_state_changed(cache);
}
//_leave(" = 0");
return 0;
stop_and_begin_cull:
switch (reason) {
case cachefiles_has_space_for_write:
fscache_count_no_write_space();
break;
case cachefiles_has_space_for_create:
fscache_count_no_create_space();
break;
default:
break;
}
begin_cull:
if (!test_and_set_bit(CACHEFILES_CULLING, &cache->flags)) {
_debug("### CULL CACHE ###");
cachefiles_state_changed(cache);
}
_leave(" = %d", ret);
return ret;
}
/*
* Mark all the objects as being out of service and queue them all for cleanup.
*/
static void cachefiles_withdraw_objects(struct cachefiles_cache *cache)
{
struct cachefiles_object *object;
unsigned int count = 0;
_enter("");
spin_lock(&cache->object_list_lock);
while (!list_empty(&cache->object_list)) {
object = list_first_entry(&cache->object_list,
struct cachefiles_object, cache_link);
cachefiles_see_object(object, cachefiles_obj_see_withdrawal);
list_del_init(&object->cache_link);
fscache_withdraw_cookie(object->cookie);
count++;
if ((count & 63) == 0) {
spin_unlock(&cache->object_list_lock);
cond_resched();
spin_lock(&cache->object_list_lock);
}
}
spin_unlock(&cache->object_list_lock);
_leave(" [%u objs]", count);
}
/*
* Withdraw fscache volumes.
*/
static void cachefiles_withdraw_fscache_volumes(struct cachefiles_cache *cache)
{
struct list_head *cur;
struct cachefiles_volume *volume;
struct fscache_volume *vcookie;
_enter("");
retry:
spin_lock(&cache->object_list_lock);
list_for_each(cur, &cache->volumes) {
volume = list_entry(cur, struct cachefiles_volume, cache_link);
if (atomic_read(&volume->vcookie->n_accesses) == 0)
continue;
vcookie = fscache_try_get_volume(volume->vcookie,
fscache_volume_get_withdraw);
if (vcookie) {
spin_unlock(&cache->object_list_lock);
fscache_withdraw_volume(vcookie);
fscache_put_volume(vcookie, fscache_volume_put_withdraw);
goto retry;
}
}
spin_unlock(&cache->object_list_lock);
_leave("");
}
/*
* Withdraw cachefiles volumes.
*/
static void cachefiles_withdraw_volumes(struct cachefiles_cache *cache)
{
_enter("");
for (;;) {
struct fscache_volume *vcookie = NULL;
struct cachefiles_volume *volume = NULL;
spin_lock(&cache->object_list_lock);
if (!list_empty(&cache->volumes)) {
volume = list_first_entry(&cache->volumes,
struct cachefiles_volume, cache_link);
vcookie = fscache_try_get_volume(volume->vcookie,
fscache_volume_get_withdraw);
if (!vcookie) {
spin_unlock(&cache->object_list_lock);
cpu_relax();
continue;
}
list_del_init(&volume->cache_link);
}
spin_unlock(&cache->object_list_lock);
if (!volume)
break;
cachefiles_withdraw_volume(volume);
fscache_put_volume(vcookie, fscache_volume_put_withdraw);
}
_leave("");
}
/*
* Sync a cache to backing disk.
*/
static void cachefiles_sync_cache(struct cachefiles_cache *cache)
{
const struct cred *saved_cred;
int ret;
_enter("%s", cache->cache->name);
/* make sure all pages pinned by operations on behalf of the netfs are
* written to disc */
cachefiles_begin_secure(cache, &saved_cred);
down_read(&cache->mnt->mnt_sb->s_umount);
ret = sync_filesystem(cache->mnt->mnt_sb);
up_read(&cache->mnt->mnt_sb->s_umount);
cachefiles_end_secure(cache, saved_cred);
if (ret == -EIO)
cachefiles_io_error(cache,
"Attempt to sync backing fs superblock returned error %d",
ret);
}
/*
* Withdraw cache objects.
*/
void cachefiles_withdraw_cache(struct cachefiles_cache *cache)
{
struct fscache_cache *fscache = cache->cache;
pr_info("File cache on %s unregistering\n", fscache->name);
fscache_withdraw_cache(fscache);
cachefiles_withdraw_fscache_volumes(cache);
/* we now have to destroy all the active objects pertaining to this
* cache - which we do by passing them off to thread pool to be
* disposed of */
cachefiles_withdraw_objects(cache);
fscache_wait_for_objects(fscache);
cachefiles_withdraw_volumes(cache);
cachefiles_sync_cache(cache);
cache->cache = NULL;
fscache_relinquish_cache(fscache);
}
Codebase Browser
linux