diff --git a/fs/super.c b/fs/super.c index 3c7e4633efeb..9cf7fc67727b 100644 --- a/fs/super.c +++ b/fs/super.c @@ -1209,17 +1209,39 @@ int get_tree_keyed(struct fs_context *fc, EXPORT_SYMBOL(get_tree_keyed); #ifdef CONFIG_BLOCK +/* + * Lock a super block that the callers holds a reference to. + * + * The caller needs to ensure that the super_block isn't being freed while + * calling this function, e.g. by holding a lock over the call to this function + * and the place that clears the pointer to the superblock used by this function + * before freeing the superblock. + */ +static bool lock_active_super(struct super_block *sb) +{ + down_read(&sb->s_umount); + if (!sb->s_root || + (sb->s_flags & (SB_ACTIVE | SB_BORN)) != (SB_ACTIVE | SB_BORN)) { + up_read(&sb->s_umount); + return false; + } + return true; +} + static void fs_mark_dead(struct block_device *bdev) { - struct super_block *sb; + struct super_block *sb = bdev->bd_holder; - sb = get_super(bdev); - if (!sb) + /* bd_holder_lock ensures that the sb isn't freed */ + lockdep_assert_held(&bdev->bd_holder_lock); + + if (!lock_active_super(sb)) return; if (sb->s_op->shutdown) sb->s_op->shutdown(sb); - drop_super(sb); + + up_read(&sb->s_umount); } static const struct blk_holder_ops fs_holder_ops = {