293 строки
6.8 KiB
C
293 строки
6.8 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Copyright (C) 2018 HUAWEI, Inc.
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* https://www.huawei.com/
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*/
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#include "internal.h"
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#include <linux/pagevec.h>
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struct page *erofs_allocpage(struct page **pagepool, gfp_t gfp)
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{
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struct page *page = *pagepool;
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if (page) {
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DBG_BUGON(page_ref_count(page) != 1);
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*pagepool = (struct page *)page_private(page);
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} else {
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page = alloc_page(gfp);
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}
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return page;
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}
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void erofs_release_pages(struct page **pagepool)
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{
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while (*pagepool) {
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struct page *page = *pagepool;
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*pagepool = (struct page *)page_private(page);
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put_page(page);
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}
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}
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#ifdef CONFIG_EROFS_FS_ZIP
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/* global shrink count (for all mounted EROFS instances) */
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static atomic_long_t erofs_global_shrink_cnt;
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static int erofs_workgroup_get(struct erofs_workgroup *grp)
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{
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int o;
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repeat:
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o = erofs_wait_on_workgroup_freezed(grp);
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if (o <= 0)
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return -1;
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if (atomic_cmpxchg(&grp->refcount, o, o + 1) != o)
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goto repeat;
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/* decrease refcount paired by erofs_workgroup_put */
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if (o == 1)
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atomic_long_dec(&erofs_global_shrink_cnt);
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return 0;
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}
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struct erofs_workgroup *erofs_find_workgroup(struct super_block *sb,
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pgoff_t index)
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{
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struct erofs_sb_info *sbi = EROFS_SB(sb);
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struct erofs_workgroup *grp;
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repeat:
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rcu_read_lock();
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grp = xa_load(&sbi->managed_pslots, index);
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if (grp) {
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if (erofs_workgroup_get(grp)) {
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/* prefer to relax rcu read side */
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rcu_read_unlock();
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goto repeat;
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}
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DBG_BUGON(index != grp->index);
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}
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rcu_read_unlock();
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return grp;
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}
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struct erofs_workgroup *erofs_insert_workgroup(struct super_block *sb,
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struct erofs_workgroup *grp)
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{
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struct erofs_sb_info *const sbi = EROFS_SB(sb);
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struct erofs_workgroup *pre;
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/*
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* Bump up a reference count before making this visible
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* to others for the XArray in order to avoid potential
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* UAF without serialized by xa_lock.
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*/
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atomic_inc(&grp->refcount);
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repeat:
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xa_lock(&sbi->managed_pslots);
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pre = __xa_cmpxchg(&sbi->managed_pslots, grp->index,
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NULL, grp, GFP_NOFS);
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if (pre) {
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if (xa_is_err(pre)) {
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pre = ERR_PTR(xa_err(pre));
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} else if (erofs_workgroup_get(pre)) {
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/* try to legitimize the current in-tree one */
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xa_unlock(&sbi->managed_pslots);
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cond_resched();
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goto repeat;
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}
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atomic_dec(&grp->refcount);
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grp = pre;
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}
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xa_unlock(&sbi->managed_pslots);
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return grp;
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}
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static void __erofs_workgroup_free(struct erofs_workgroup *grp)
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{
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atomic_long_dec(&erofs_global_shrink_cnt);
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erofs_workgroup_free_rcu(grp);
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}
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int erofs_workgroup_put(struct erofs_workgroup *grp)
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{
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int count = atomic_dec_return(&grp->refcount);
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if (count == 1)
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atomic_long_inc(&erofs_global_shrink_cnt);
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else if (!count)
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__erofs_workgroup_free(grp);
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return count;
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}
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static bool erofs_try_to_release_workgroup(struct erofs_sb_info *sbi,
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struct erofs_workgroup *grp)
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{
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/*
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* If managed cache is on, refcount of workgroups
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* themselves could be < 0 (freezed). In other words,
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* there is no guarantee that all refcounts > 0.
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*/
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if (!erofs_workgroup_try_to_freeze(grp, 1))
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return false;
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/*
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* Note that all cached pages should be unattached
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* before deleted from the XArray. Otherwise some
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* cached pages could be still attached to the orphan
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* old workgroup when the new one is available in the tree.
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*/
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if (erofs_try_to_free_all_cached_pages(sbi, grp)) {
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erofs_workgroup_unfreeze(grp, 1);
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return false;
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}
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/*
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* It's impossible to fail after the workgroup is freezed,
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* however in order to avoid some race conditions, add a
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* DBG_BUGON to observe this in advance.
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*/
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DBG_BUGON(__xa_erase(&sbi->managed_pslots, grp->index) != grp);
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/* last refcount should be connected with its managed pslot. */
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erofs_workgroup_unfreeze(grp, 0);
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__erofs_workgroup_free(grp);
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return true;
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}
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static unsigned long erofs_shrink_workstation(struct erofs_sb_info *sbi,
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unsigned long nr_shrink)
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{
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struct erofs_workgroup *grp;
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unsigned int freed = 0;
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unsigned long index;
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xa_lock(&sbi->managed_pslots);
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xa_for_each(&sbi->managed_pslots, index, grp) {
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/* try to shrink each valid workgroup */
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if (!erofs_try_to_release_workgroup(sbi, grp))
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continue;
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xa_unlock(&sbi->managed_pslots);
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++freed;
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if (!--nr_shrink)
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return freed;
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xa_lock(&sbi->managed_pslots);
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}
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xa_unlock(&sbi->managed_pslots);
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return freed;
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}
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/* protected by 'erofs_sb_list_lock' */
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static unsigned int shrinker_run_no;
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/* protects the mounted 'erofs_sb_list' */
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static DEFINE_SPINLOCK(erofs_sb_list_lock);
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static LIST_HEAD(erofs_sb_list);
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void erofs_shrinker_register(struct super_block *sb)
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{
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struct erofs_sb_info *sbi = EROFS_SB(sb);
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mutex_init(&sbi->umount_mutex);
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spin_lock(&erofs_sb_list_lock);
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list_add(&sbi->list, &erofs_sb_list);
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spin_unlock(&erofs_sb_list_lock);
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}
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void erofs_shrinker_unregister(struct super_block *sb)
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{
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struct erofs_sb_info *const sbi = EROFS_SB(sb);
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mutex_lock(&sbi->umount_mutex);
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/* clean up all remaining workgroups in memory */
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erofs_shrink_workstation(sbi, ~0UL);
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spin_lock(&erofs_sb_list_lock);
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list_del(&sbi->list);
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spin_unlock(&erofs_sb_list_lock);
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mutex_unlock(&sbi->umount_mutex);
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}
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static unsigned long erofs_shrink_count(struct shrinker *shrink,
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struct shrink_control *sc)
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{
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return atomic_long_read(&erofs_global_shrink_cnt);
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}
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static unsigned long erofs_shrink_scan(struct shrinker *shrink,
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struct shrink_control *sc)
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{
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struct erofs_sb_info *sbi;
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struct list_head *p;
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unsigned long nr = sc->nr_to_scan;
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unsigned int run_no;
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unsigned long freed = 0;
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spin_lock(&erofs_sb_list_lock);
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do {
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run_no = ++shrinker_run_no;
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} while (run_no == 0);
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/* Iterate over all mounted superblocks and try to shrink them */
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p = erofs_sb_list.next;
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while (p != &erofs_sb_list) {
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sbi = list_entry(p, struct erofs_sb_info, list);
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/*
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* We move the ones we do to the end of the list, so we stop
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* when we see one we have already done.
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*/
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if (sbi->shrinker_run_no == run_no)
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break;
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if (!mutex_trylock(&sbi->umount_mutex)) {
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p = p->next;
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continue;
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}
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spin_unlock(&erofs_sb_list_lock);
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sbi->shrinker_run_no = run_no;
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freed += erofs_shrink_workstation(sbi, nr - freed);
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spin_lock(&erofs_sb_list_lock);
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/* Get the next list element before we move this one */
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p = p->next;
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/*
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* Move this one to the end of the list to provide some
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* fairness.
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*/
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list_move_tail(&sbi->list, &erofs_sb_list);
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mutex_unlock(&sbi->umount_mutex);
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if (freed >= nr)
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break;
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}
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spin_unlock(&erofs_sb_list_lock);
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return freed;
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}
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static struct shrinker erofs_shrinker_info = {
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.scan_objects = erofs_shrink_scan,
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.count_objects = erofs_shrink_count,
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.seeks = DEFAULT_SEEKS,
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};
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int __init erofs_init_shrinker(void)
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{
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return register_shrinker(&erofs_shrinker_info, "erofs-shrinker");
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}
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void erofs_exit_shrinker(void)
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{
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unregister_shrinker(&erofs_shrinker_info);
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}
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#endif /* !CONFIG_EROFS_FS_ZIP */
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