blob: 5f61f99f4c10fcc58a7154e182994a0a1d70da22 [file] [log] [blame]
// SPDX-License-Identifier: GPL-2.0
/*
* linux/drivers/staging/erofs/utils.c
*
* Copyright (C) 2018 HUAWEI, Inc.
* http://www.huawei.com/
* Created by Gao Xiang <gaoxiang25@huawei.com>
*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file COPYING in the main directory of the Linux
* distribution for more details.
*/
#include "internal.h"
#include <linux/pagevec.h>
struct page *erofs_allocpage(struct list_head *pool, gfp_t gfp)
{
struct page *page;
if (!list_empty(pool)) {
page = lru_to_page(pool);
list_del(&page->lru);
} else {
page = alloc_pages(gfp | __GFP_NOFAIL, 0);
}
return page;
}
/* global shrink count (for all mounted EROFS instances) */
static atomic_long_t erofs_global_shrink_cnt;
#ifdef CONFIG_EROFS_FS_ZIP
#define __erofs_workgroup_get(grp) atomic_inc(&(grp)->refcount)
#define __erofs_workgroup_put(grp) atomic_dec(&(grp)->refcount)
static int erofs_workgroup_get(struct erofs_workgroup *grp)
{
int o;
repeat:
o = erofs_wait_on_workgroup_freezed(grp);
if (unlikely(o <= 0))
return -1;
if (unlikely(atomic_cmpxchg(&grp->refcount, o, o + 1) != o))
goto repeat;
/* decrease refcount paired by erofs_workgroup_put */
if (unlikely(o == 1))
atomic_long_dec(&erofs_global_shrink_cnt);
return 0;
}
struct erofs_workgroup *erofs_find_workgroup(struct super_block *sb,
pgoff_t index, bool *tag)
{
struct erofs_sb_info *sbi = EROFS_SB(sb);
struct erofs_workgroup *grp;
repeat:
rcu_read_lock();
grp = radix_tree_lookup(&sbi->workstn_tree, index);
if (grp != NULL) {
*tag = xa_pointer_tag(grp);
grp = xa_untag_pointer(grp);
if (erofs_workgroup_get(grp)) {
/* prefer to relax rcu read side */
rcu_read_unlock();
goto repeat;
}
DBG_BUGON(index != grp->index);
}
rcu_read_unlock();
return grp;
}
int erofs_register_workgroup(struct super_block *sb,
struct erofs_workgroup *grp,
bool tag)
{
struct erofs_sb_info *sbi;
int err;
/* grp shouldn't be broken or used before */
if (unlikely(atomic_read(&grp->refcount) != 1)) {
DBG_BUGON(1);
return -EINVAL;
}
err = radix_tree_preload(GFP_NOFS);
if (err)
return err;
sbi = EROFS_SB(sb);
erofs_workstn_lock(sbi);
grp = xa_tag_pointer(grp, tag);
/*
* Bump up reference count before making this workgroup
* visible to other users in order to avoid potential UAF
* without serialized by erofs_workstn_lock.
*/
__erofs_workgroup_get(grp);
err = radix_tree_insert(&sbi->workstn_tree,
grp->index, grp);
if (unlikely(err))
/*
* it's safe to decrease since the workgroup isn't visible
* and refcount >= 2 (cannot be freezed).
*/
__erofs_workgroup_put(grp);
erofs_workstn_unlock(sbi);
radix_tree_preload_end();
return err;
}
static void __erofs_workgroup_free(struct erofs_workgroup *grp)
{
atomic_long_dec(&erofs_global_shrink_cnt);
erofs_workgroup_free_rcu(grp);
}
int erofs_workgroup_put(struct erofs_workgroup *grp)
{
int count = atomic_dec_return(&grp->refcount);
if (count == 1)
atomic_long_inc(&erofs_global_shrink_cnt);
else if (!count)
__erofs_workgroup_free(grp);
return count;
}
#ifdef EROFS_FS_HAS_MANAGED_CACHE
/* for cache-managed case, customized reclaim paths exist */
static void erofs_workgroup_unfreeze_final(struct erofs_workgroup *grp)
{
erofs_workgroup_unfreeze(grp, 0);
__erofs_workgroup_free(grp);
}
static bool erofs_try_to_release_workgroup(struct erofs_sb_info *sbi,
struct erofs_workgroup *grp,
bool cleanup)
{
/*
* for managed cache enabled, the refcount of workgroups
* themselves could be < 0 (freezed). So there is no guarantee
* that all refcount > 0 if managed cache is enabled.
*/
if (!erofs_workgroup_try_to_freeze(grp, 1))
return false;
/*
* note that all cached pages should be unlinked
* before delete it from the radix tree.
* Otherwise some cached pages of an orphan old workgroup
* could be still linked after the new one is available.
*/
if (erofs_try_to_free_all_cached_pages(sbi, grp)) {
erofs_workgroup_unfreeze(grp, 1);
return false;
}
/*
* it is impossible to fail after the workgroup is freezed,
* however in order to avoid some race conditions, add a
* DBG_BUGON to observe this in advance.
*/
DBG_BUGON(xa_untag_pointer(radix_tree_delete(&sbi->workstn_tree,
grp->index)) != grp);
/*
* if managed cache is enable, the last refcount
* should indicate the related workstation.
*/
erofs_workgroup_unfreeze_final(grp);
return true;
}
#else
/* for nocache case, no customized reclaim path at all */
static bool erofs_try_to_release_workgroup(struct erofs_sb_info *sbi,
struct erofs_workgroup *grp,
bool cleanup)
{
int cnt = atomic_read(&grp->refcount);
DBG_BUGON(cnt <= 0);
DBG_BUGON(cleanup && cnt != 1);
if (cnt > 1)
return false;
DBG_BUGON(xa_untag_pointer(radix_tree_delete(&sbi->workstn_tree,
grp->index)) != grp);
/* (rarely) could be grabbed again when freeing */
erofs_workgroup_put(grp);
return true;
}
#endif
unsigned long erofs_shrink_workstation(struct erofs_sb_info *sbi,
unsigned long nr_shrink,
bool cleanup)
{
pgoff_t first_index = 0;
void *batch[PAGEVEC_SIZE];
unsigned int freed = 0;
int i, found;
repeat:
erofs_workstn_lock(sbi);
found = radix_tree_gang_lookup(&sbi->workstn_tree,
batch, first_index, PAGEVEC_SIZE);
for (i = 0; i < found; ++i) {
struct erofs_workgroup *grp = xa_untag_pointer(batch[i]);
first_index = grp->index + 1;
/* try to shrink each valid workgroup */
if (!erofs_try_to_release_workgroup(sbi, grp, cleanup))
continue;
++freed;
if (unlikely(!--nr_shrink))
break;
}
erofs_workstn_unlock(sbi);
if (i && nr_shrink)
goto repeat;
return freed;
}
#endif
/* protected by 'erofs_sb_list_lock' */
static unsigned int shrinker_run_no;
/* protects the mounted 'erofs_sb_list' */
static DEFINE_SPINLOCK(erofs_sb_list_lock);
static LIST_HEAD(erofs_sb_list);
void erofs_register_super(struct super_block *sb)
{
struct erofs_sb_info *sbi = EROFS_SB(sb);
mutex_init(&sbi->umount_mutex);
spin_lock(&erofs_sb_list_lock);
list_add(&sbi->list, &erofs_sb_list);
spin_unlock(&erofs_sb_list_lock);
}
void erofs_unregister_super(struct super_block *sb)
{
spin_lock(&erofs_sb_list_lock);
list_del(&EROFS_SB(sb)->list);
spin_unlock(&erofs_sb_list_lock);
}
static unsigned long erofs_shrink_count(struct shrinker *shrink,
struct shrink_control *sc)
{
return atomic_long_read(&erofs_global_shrink_cnt);
}
static unsigned long erofs_shrink_scan(struct shrinker *shrink,
struct shrink_control *sc)
{
struct erofs_sb_info *sbi;
struct list_head *p;
unsigned long nr = sc->nr_to_scan;
unsigned int run_no;
unsigned long freed = 0;
spin_lock(&erofs_sb_list_lock);
do
run_no = ++shrinker_run_no;
while (run_no == 0);
/* Iterate over all mounted superblocks and try to shrink them */
p = erofs_sb_list.next;
while (p != &erofs_sb_list) {
sbi = list_entry(p, struct erofs_sb_info, list);
/*
* We move the ones we do to the end of the list, so we stop
* when we see one we have already done.
*/
if (sbi->shrinker_run_no == run_no)
break;
if (!mutex_trylock(&sbi->umount_mutex)) {
p = p->next;
continue;
}
spin_unlock(&erofs_sb_list_lock);
sbi->shrinker_run_no = run_no;
#ifdef CONFIG_EROFS_FS_ZIP
freed += erofs_shrink_workstation(sbi, nr, false);
#endif
spin_lock(&erofs_sb_list_lock);
/* Get the next list element before we move this one */
p = p->next;
/*
* Move this one to the end of the list to provide some
* fairness.
*/
list_move_tail(&sbi->list, &erofs_sb_list);
mutex_unlock(&sbi->umount_mutex);
if (freed >= nr)
break;
}
spin_unlock(&erofs_sb_list_lock);
return freed;
}
struct shrinker erofs_shrinker_info = {
.scan_objects = erofs_shrink_scan,
.count_objects = erofs_shrink_count,
.seeks = DEFAULT_SEEKS,
};