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staging: erofs: introduce workstation for decompression
This patch introduces another concept used by the unzip subsystem called 'workstation'. It can be seen as a sparse array that stores pointers pointed to data structures related to the corresponding physical blocks. All lookup cases are protected by RCU read lock. Besides, reference count and spin_lock are also introduced to manage its lifetime and serialize all update operations. 'workstation' is currently implemented on the in-kernel radix tree approach for backward compatibility. With the evolution of linux kernel, it could be migrated into XArray implementation in the future. Signed-off-by: Gao Xiang <gaoxiang25@huawei.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Gao Xiang
Greg Kroah-Hartman
parent
a158131262
commit
e7e9a307be
@ -79,6 +79,9 @@ struct erofs_sb_info {
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#ifdef CONFIG_EROFS_FS_ZIP
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/* cluster size in bit shift */
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unsigned char clusterbits;
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/* the dedicated workstation for compression */
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struct radix_tree_root workstn_tree;
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#endif
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u32 build_time_nsec;
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@ -149,6 +152,96 @@ static inline void *erofs_kmalloc(struct erofs_sb_info *sbi,
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#define set_opt(sbi, option) ((sbi)->mount_opt |= EROFS_MOUNT_##option)
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#define test_opt(sbi, option) ((sbi)->mount_opt & EROFS_MOUNT_##option)
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#ifdef CONFIG_EROFS_FS_ZIP
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#define erofs_workstn_lock(sbi) xa_lock(&(sbi)->workstn_tree)
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#define erofs_workstn_unlock(sbi) xa_unlock(&(sbi)->workstn_tree)
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/* basic unit of the workstation of a super_block */
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struct erofs_workgroup {
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/* the workgroup index in the workstation */
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pgoff_t index;
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/* overall workgroup reference count */
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atomic_t refcount;
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};
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#define EROFS_LOCKED_MAGIC (INT_MIN | 0xE0F510CCL)
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static inline bool erofs_workgroup_try_to_freeze(
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struct erofs_workgroup *grp, int v)
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{
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#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
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if (v != atomic_cmpxchg(&grp->refcount,
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v, EROFS_LOCKED_MAGIC))
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return false;
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preempt_disable();
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#else
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preempt_disable();
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if (atomic_read(&grp->refcount) != v) {
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preempt_enable();
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return false;
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}
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#endif
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return true;
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}
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static inline void erofs_workgroup_unfreeze(
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struct erofs_workgroup *grp, int v)
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{
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#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
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atomic_set(&grp->refcount, v);
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#endif
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preempt_enable();
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}
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static inline bool erofs_workgroup_get(struct erofs_workgroup *grp, int *ocnt)
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{
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const int locked = (int)EROFS_LOCKED_MAGIC;
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int o;
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repeat:
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o = atomic_read(&grp->refcount);
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/* spin if it is temporarily locked at the reclaim path */
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if (unlikely(o == locked)) {
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#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
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do
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cpu_relax();
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while (atomic_read(&grp->refcount) == locked);
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#endif
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goto repeat;
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}
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if (unlikely(o <= 0))
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return -1;
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if (unlikely(atomic_cmpxchg(&grp->refcount, o, o + 1) != o))
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goto repeat;
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*ocnt = o;
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return 0;
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}
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#define __erofs_workgroup_get(grp) atomic_inc(&(grp)->refcount)
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extern int erofs_workgroup_put(struct erofs_workgroup *grp);
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extern struct erofs_workgroup *erofs_find_workgroup(
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struct super_block *sb, pgoff_t index, bool *tag);
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extern int erofs_register_workgroup(struct super_block *sb,
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struct erofs_workgroup *grp, bool tag);
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extern unsigned long erofs_shrink_workstation(struct erofs_sb_info *sbi,
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unsigned long nr_shrink, bool cleanup);
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static inline void erofs_workstation_cleanup_all(struct super_block *sb)
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{
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erofs_shrink_workstation(EROFS_SB(sb), ~0UL, true);
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}
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#endif
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/* we strictly follow PAGE_SIZE and no buffer head yet */
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#define LOG_BLOCK_SIZE PAGE_SHIFT
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@ -296,6 +296,10 @@ static int erofs_read_super(struct super_block *sb,
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if (!silent)
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infoln("root inode @ nid %llu", ROOT_NID(sbi));
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#ifdef CONFIG_EROFS_FS_ZIP
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INIT_RADIX_TREE(&sbi->workstn_tree, GFP_ATOMIC);
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#endif
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/* get the root inode */
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inode = erofs_iget(sb, ROOT_NID(sbi), true);
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if (IS_ERR(inode)) {
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@ -376,6 +380,11 @@ static void erofs_put_super(struct super_block *sb)
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__putname(sbi->dev_name);
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mutex_lock(&sbi->umount_mutex);
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#ifdef CONFIG_EROFS_FS_ZIP
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erofs_workstation_cleanup_all(sb);
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#endif
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erofs_unregister_super(sb);
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mutex_unlock(&sbi->umount_mutex);
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@ -29,6 +29,83 @@ struct page *erofs_allocpage(struct list_head *pool, gfp_t gfp)
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return page;
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}
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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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#ifdef CONFIG_EROFS_FS_ZIP
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/* radix_tree and the future XArray both don't use tagptr_t yet */
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struct erofs_workgroup *erofs_find_workgroup(
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struct super_block *sb, pgoff_t index, bool *tag)
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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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int oldcount;
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repeat:
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rcu_read_lock();
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grp = radix_tree_lookup(&sbi->workstn_tree, index);
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if (grp != NULL) {
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*tag = radix_tree_exceptional_entry(grp);
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grp = (void *)((unsigned long)grp &
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~RADIX_TREE_EXCEPTIONAL_ENTRY);
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if (erofs_workgroup_get(grp, &oldcount)) {
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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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/* decrease refcount added by erofs_workgroup_put */
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if (unlikely(oldcount == 1))
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atomic_long_dec(&erofs_global_shrink_cnt);
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BUG_ON(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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int erofs_register_workgroup(struct super_block *sb,
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struct erofs_workgroup *grp,
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bool tag)
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{
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struct erofs_sb_info *sbi;
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int err;
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/* grp->refcount should not < 1 */
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BUG_ON(!atomic_read(&grp->refcount));
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err = radix_tree_preload(GFP_NOFS);
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if (err)
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return err;
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sbi = EROFS_SB(sb);
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erofs_workstn_lock(sbi);
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if (tag)
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grp = (void *)((unsigned long)grp |
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1UL << RADIX_TREE_EXCEPTIONAL_SHIFT);
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err = radix_tree_insert(&sbi->workstn_tree,
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grp->index, grp);
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if (!err) {
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__erofs_workgroup_get(grp);
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}
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erofs_workstn_unlock(sbi);
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radix_tree_preload_end();
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return err;
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}
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unsigned long erofs_shrink_workstation(struct erofs_sb_info *sbi,
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unsigned long nr_shrink,
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bool cleanup)
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{
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return 0;
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}
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#endif
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/* protected by 'erofs_sb_list_lock' */
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static unsigned int shrinker_run_no;
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@ -37,9 +114,6 @@ static unsigned int shrinker_run_no;
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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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/* global shrink count (for all mounted EROFS instances) */
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static atomic_long_t erofs_global_shrink_cnt;
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void erofs_register_super(struct super_block *sb)
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{
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struct erofs_sb_info *sbi = EROFS_SB(sb);
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@ -112,6 +186,7 @@ unsigned long erofs_shrink_scan(struct shrinker *shrink,
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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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freed += erofs_shrink_workstation(sbi, nr, false);
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if (freed >= nr)
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break;
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}
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