diff options
| -rw-r--r-- | fs/dcache.c | 66 | ||||
| -rw-r--r-- | fs/super.c | 2 | ||||
| -rw-r--r-- | include/linux/dcache.h | 2 |
3 files changed, 62 insertions, 8 deletions
diff --git a/fs/dcache.c b/fs/dcache.c index 940d188..385f5db 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -382,6 +382,8 @@ static inline void prune_one_dentry(struct dentry * dentry) /** * prune_dcache - shrink the dcache * @count: number of entries to try and free + * @sb: if given, ignore dentries for other superblocks + * which are being unmounted. * * Shrink the dcache. This is done when we need * more memory, or simply when we need to unmount @@ -392,16 +394,29 @@ static inline void prune_one_dentry(struct dentry * dentry) * all the dentries are in use. */ -static void prune_dcache(int count) +static void prune_dcache(int count, struct super_block *sb) { spin_lock(&dcache_lock); for (; count ; count--) { struct dentry *dentry; struct list_head *tmp; + struct rw_semaphore *s_umount; cond_resched_lock(&dcache_lock); tmp = dentry_unused.prev; + if (unlikely(sb)) { + /* Try to find a dentry for this sb, but don't try + * too hard, if they aren't near the tail they will + * be moved down again soon + */ + int skip = count; + while (skip && tmp != &dentry_unused && + list_entry(tmp, struct dentry, d_lru)->d_sb != sb) { + skip--; + tmp = tmp->prev; + } + } if (tmp == &dentry_unused) break; list_del_init(tmp); @@ -427,7 +442,45 @@ static void prune_dcache(int count) spin_unlock(&dentry->d_lock); continue; } - prune_one_dentry(dentry); + /* + * If the dentry is not DCACHED_REFERENCED, it is time + * to remove it from the dcache, provided the super block is + * NULL (which means we are trying to reclaim memory) + * or this dentry belongs to the same super block that + * we want to shrink. + */ + /* + * If this dentry is for "my" filesystem, then I can prune it + * without taking the s_umount lock (I already hold it). + */ + if (sb && dentry->d_sb == sb) { + prune_one_dentry(dentry); + continue; + } + /* + * ...otherwise we need to be sure this filesystem isn't being + * unmounted, otherwise we could race with + * generic_shutdown_super(), and end up holding a reference to + * an inode while the filesystem is unmounted. + * So we try to get s_umount, and make sure s_root isn't NULL. + * (Take a local copy of s_umount to avoid a use-after-free of + * `dentry'). + */ + s_umount = &dentry->d_sb->s_umount; + if (down_read_trylock(s_umount)) { + if (dentry->d_sb->s_root != NULL) { + prune_one_dentry(dentry); + up_read(s_umount); + continue; + } + up_read(s_umount); + } + spin_unlock(&dentry->d_lock); + /* Cannot remove the first dentry, and it isn't appropriate + * to move it to the head of the list, so give up, and try + * later + */ + break; } spin_unlock(&dcache_lock); } @@ -630,7 +683,7 @@ void shrink_dcache_parent(struct dentry * parent) int found; while ((found = select_parent(parent)) != 0) - prune_dcache(found); + prune_dcache(found, parent->d_sb); } /** @@ -643,9 +696,10 @@ void shrink_dcache_parent(struct dentry * parent) * done under dcache_lock. * */ -void shrink_dcache_anon(struct hlist_head *head) +void shrink_dcache_anon(struct super_block *sb) { struct hlist_node *lp; + struct hlist_head *head = &sb->s_anon; int found; do { found = 0; @@ -668,7 +722,7 @@ void shrink_dcache_anon(struct hlist_head *head) } } spin_unlock(&dcache_lock); - prune_dcache(found); + prune_dcache(found, sb); } while(found); } @@ -689,7 +743,7 @@ static int shrink_dcache_memory(int nr, gfp_t gfp_mask) if (nr) { if (!(gfp_mask & __GFP_FS)) return -1; - prune_dcache(nr); + prune_dcache(nr, NULL); } return (dentry_stat.nr_unused / 100) * sysctl_vfs_cache_pressure; } @@ -231,7 +231,7 @@ void generic_shutdown_super(struct super_block *sb) if (root) { sb->s_root = NULL; shrink_dcache_parent(root); - shrink_dcache_anon(&sb->s_anon); + shrink_dcache_anon(sb); dput(root); fsync_super(sb); lock_super(sb); diff --git a/include/linux/dcache.h b/include/linux/dcache.h index 836325e..46d0e07 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -217,7 +217,7 @@ extern struct dentry * d_alloc_anon(struct inode *); extern struct dentry * d_splice_alias(struct inode *, struct dentry *); extern void shrink_dcache_sb(struct super_block *); extern void shrink_dcache_parent(struct dentry *); -extern void shrink_dcache_anon(struct hlist_head *); +extern void shrink_dcache_anon(struct super_block *); extern int d_invalidate(struct dentry *); /* only used at mount-time */ |
