diff options
Diffstat (limited to 'fs/super.c')
| -rw-r--r-- | fs/super.c | 51 |
1 files changed, 50 insertions, 1 deletions
@@ -38,6 +38,48 @@ LIST_HEAD(super_blocks); DEFINE_SPINLOCK(sb_lock); +/* + * One thing we have to be careful of with a per-sb shrinker is that we don't + * drop the last active reference to the superblock from within the shrinker. + * If that happens we could trigger unregistering the shrinker from within the + * shrinker path and that leads to deadlock on the shrinker_rwsem. Hence we + * take a passive reference to the superblock to avoid this from occurring. + */ +static int prune_super(struct shrinker *shrink, struct shrink_control *sc) +{ + struct super_block *sb; + int count; + + sb = container_of(shrink, struct super_block, s_shrink); + + /* + * Deadlock avoidance. We may hold various FS locks, and we don't want + * to recurse into the FS that called us in clear_inode() and friends.. + */ + if (sc->nr_to_scan && !(sc->gfp_mask & __GFP_FS)) + return -1; + + if (!grab_super_passive(sb)) + return -1; + + if (sc->nr_to_scan) { + /* proportion the scan between the two caches */ + int total; + + total = sb->s_nr_dentry_unused + sb->s_nr_inodes_unused + 1; + count = (sc->nr_to_scan * sb->s_nr_dentry_unused) / total; + + /* prune dcache first as icache is pinned by it */ + prune_dcache_sb(sb, count); + prune_icache_sb(sb, sc->nr_to_scan - count); + } + + count = ((sb->s_nr_dentry_unused + sb->s_nr_inodes_unused) / 100) + * sysctl_vfs_cache_pressure; + drop_super(sb); + return count; +} + /** * alloc_super - create new superblock * @type: filesystem type superblock should belong to @@ -116,6 +158,9 @@ static struct super_block *alloc_super(struct file_system_type *type) s->s_op = &default_op; s->s_time_gran = 1000000000; s->cleancache_poolid = -1; + + s->s_shrink.seeks = DEFAULT_SEEKS; + s->s_shrink.shrink = prune_super; } out: return s; @@ -183,6 +228,10 @@ void deactivate_locked_super(struct super_block *s) if (atomic_dec_and_test(&s->s_active)) { cleancache_flush_fs(s); fs->kill_sb(s); + + /* caches are now gone, we can safely kill the shrinker now */ + unregister_shrinker(&s->s_shrink); + /* * We need to call rcu_barrier so all the delayed rcu free * inodes are flushed before we release the fs module. @@ -311,7 +360,6 @@ void generic_shutdown_super(struct super_block *sb) { const struct super_operations *sop = sb->s_op; - if (sb->s_root) { shrink_dcache_for_umount(sb); sync_filesystem(sb); @@ -399,6 +447,7 @@ retry: list_add(&s->s_instances, &type->fs_supers); spin_unlock(&sb_lock); get_filesystem(type); + register_shrinker(&s->s_shrink); return s; } |
