| // SPDX-License-Identifier: GPL-2.0-only |
| /* |
| * Copyright (C) 2018 HUAWEI, Inc. |
| * http://www.huawei.com/ |
| * Created by Gao Xiang <gaoxiang25@huawei.com> |
| */ |
| #include "internal.h" |
| #include <linux/pagevec.h> |
| |
| struct page *erofs_allocpage(struct list_head *pool, gfp_t gfp, bool nofail) |
| { |
| 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_pages(gfp | (nofail ? __GFP_NOFAIL : 0), 0); |
| } |
| return page; |
| } |
| |
| #if (EROFS_PCPUBUF_NR_PAGES > 0) |
| static struct { |
| u8 data[PAGE_SIZE * EROFS_PCPUBUF_NR_PAGES]; |
| } ____cacheline_aligned_in_smp erofs_pcpubuf[NR_CPUS]; |
| |
| void *erofs_get_pcpubuf(unsigned int pagenr) |
| { |
| preempt_disable(); |
| return &erofs_pcpubuf[smp_processor_id()].data[pagenr * PAGE_SIZE]; |
| } |
| #endif |
| |
| #ifdef CONFIG_EROFS_FS_ZIP |
| /* global shrink count (for all mounted EROFS instances) */ |
| static atomic_long_t erofs_global_shrink_cnt; |
| |
| #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 (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, 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) { |
| *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 (atomic_read(&grp->refcount) != 1) { |
| DBG_BUGON(1); |
| return -EINVAL; |
| } |
| |
| err = radix_tree_preload(GFP_NOFS); |
| if (err) |
| return err; |
| |
| sbi = EROFS_SB(sb); |
| xa_lock(&sbi->workstn_tree); |
| |
| 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 workstn_lock. |
| */ |
| __erofs_workgroup_get(grp); |
| |
| err = radix_tree_insert(&sbi->workstn_tree, grp->index, grp); |
| if (err) |
| /* |
| * it's safe to decrease since the workgroup isn't visible |
| * and refcount >= 2 (cannot be freezed). |
| */ |
| __erofs_workgroup_put(grp); |
| |
| xa_unlock(&sbi->workstn_tree); |
| 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; |
| } |
| |
| 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) |
| { |
| /* |
| * 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 radix tree. 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_untag_pointer(radix_tree_delete(&sbi->workstn_tree, |
| grp->index)) != grp); |
| |
| /* |
| * If managed cache is on, last refcount should indicate |
| * the related workstation. |
| */ |
| erofs_workgroup_unfreeze_final(grp); |
| return true; |
| } |
| |
| static unsigned long erofs_shrink_workstation(struct erofs_sb_info *sbi, |
| unsigned long nr_shrink) |
| { |
| pgoff_t first_index = 0; |
| void *batch[PAGEVEC_SIZE]; |
| unsigned int freed = 0; |
| |
| int i, found; |
| repeat: |
| xa_lock(&sbi->workstn_tree); |
| |
| 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)) |
| continue; |
| |
| ++freed; |
| if (!--nr_shrink) |
| break; |
| } |
| xa_unlock(&sbi->workstn_tree); |
| |
| if (i && nr_shrink) |
| goto repeat; |
| 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); |
| |
| 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 */ |
| |