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Brooklyn/fs/erofs/utils.c
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2022-03-15 21:13:23 +05:00

284 lines
6.6 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 2018 HUAWEI, Inc.
* https://www.huawei.com/
*/
#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);
DBG_BUGON(page_ref_count(page) != 1);
list_del(&page->lru);
} else {
page = alloc_page(gfp);
}
return page;
}
#ifdef CONFIG_EROFS_FS_ZIP
/* global shrink count (for all mounted EROFS instances) */
static atomic_long_t erofs_global_shrink_cnt;
static int erofs_workgroup_get(struct erofs_workgroup *grp)
{
int o;
repeat:
o = erofs_wait_on_workgroup_freezed(grp);
if (o <= 0)
return -1;
if (atomic_cmpxchg(&grp->refcount, o, o + 1) != o)
goto repeat;
/* decrease refcount paired by erofs_workgroup_put */
if (o == 1)
atomic_long_dec(&erofs_global_shrink_cnt);
return 0;
}
struct erofs_workgroup *erofs_find_workgroup(struct super_block *sb,
pgoff_t index)
{
struct erofs_sb_info *sbi = EROFS_SB(sb);
struct erofs_workgroup *grp;
repeat:
rcu_read_lock();
grp = xa_load(&sbi->managed_pslots, index);
if (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;
}
struct erofs_workgroup *erofs_insert_workgroup(struct super_block *sb,
struct erofs_workgroup *grp)
{
struct erofs_sb_info *const sbi = EROFS_SB(sb);
struct erofs_workgroup *pre;
/*
* Bump up a reference count before making this visible
* to others for the XArray in order to avoid potential
* UAF without serialized by xa_lock.
*/
atomic_inc(&grp->refcount);
repeat:
xa_lock(&sbi->managed_pslots);
pre = __xa_cmpxchg(&sbi->managed_pslots, grp->index,
NULL, grp, GFP_NOFS);
if (pre) {
if (xa_is_err(pre)) {
pre = ERR_PTR(xa_err(pre));
} else if (erofs_workgroup_get(pre)) {
/* try to legitimize the current in-tree one */
xa_unlock(&sbi->managed_pslots);
cond_resched();
goto repeat;
}
atomic_dec(&grp->refcount);
grp = pre;
}
xa_unlock(&sbi->managed_pslots);
return grp;
}
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;
}
static bool erofs_try_to_release_workgroup(struct erofs_sb_info *sbi,
struct erofs_workgroup *grp)
{
/*
* If managed cache is on, refcount of workgroups
* themselves could be < 0 (freezed). In other words,
* there is no guarantee that all refcounts > 0.
*/
if (!erofs_workgroup_try_to_freeze(grp, 1))
return false;
/*
* Note that all cached pages should be unattached
* before deleted from the XArray. Otherwise some
* cached pages could be still attached to the orphan
* old workgroup when the new one is available in the tree.
*/
if (erofs_try_to_free_all_cached_pages(sbi, grp)) {
erofs_workgroup_unfreeze(grp, 1);
return false;
}
/*
* It's 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_erase(&sbi->managed_pslots, grp->index) != grp);
/* last refcount should be connected with its managed pslot. */
erofs_workgroup_unfreeze(grp, 0);
__erofs_workgroup_free(grp);
return true;
}
static unsigned long erofs_shrink_workstation(struct erofs_sb_info *sbi,
unsigned long nr_shrink)
{
struct erofs_workgroup *grp;
unsigned int freed = 0;
unsigned long index;
xa_lock(&sbi->managed_pslots);
xa_for_each(&sbi->managed_pslots, index, grp) {
/* try to shrink each valid workgroup */
if (!erofs_try_to_release_workgroup(sbi, grp))
continue;
xa_unlock(&sbi->managed_pslots);
++freed;
if (!--nr_shrink)
return freed;
xa_lock(&sbi->managed_pslots);
}
xa_unlock(&sbi->managed_pslots);
return freed;
}
/* 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_shrinker_register(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_shrinker_unregister(struct super_block *sb)
{
struct erofs_sb_info *const sbi = EROFS_SB(sb);
mutex_lock(&sbi->umount_mutex);
/* clean up all remaining workgroups in memory */
erofs_shrink_workstation(sbi, ~0UL);
spin_lock(&erofs_sb_list_lock);
list_del(&sbi->list);
spin_unlock(&erofs_sb_list_lock);
mutex_unlock(&sbi->umount_mutex);
}
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;
freed += erofs_shrink_workstation(sbi, nr - freed);
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;
}
static struct shrinker erofs_shrinker_info = {
.scan_objects = erofs_shrink_scan,
.count_objects = erofs_shrink_count,
.seeks = DEFAULT_SEEKS,
};
int __init erofs_init_shrinker(void)
{
return register_shrinker(&erofs_shrinker_info);
}
void erofs_exit_shrinker(void)
{
unregister_shrinker(&erofs_shrinker_info);
}
#endif /* !CONFIG_EROFS_FS_ZIP */