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Commit 619c8c76 authored by Ian Kent's avatar Ian Kent Committed by Chris Mason
Browse files

Btrfs - fix race between btrfs_get_sb() and umount 



When mounting a btrfs file system btrfs_test_super() may attempt to
use sb->s_fs_info, the btrfs root, of a super block that is going away
and that has had the btrfs root set to NULL in its ->put_super(). But
if the super block is going away it cannot be an existing super block
so we can return false in this case.

Signed-off-by: default avatarIan Kent <raven@themaw.net>
Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
parent bc1cbf1f

fs/btrfs/super.c

+6 −0
Original line number Diff line number Diff line
@@ -566,6 +566,12 @@ static int btrfs_test_super(struct super_block *s, void *data) 
	struct btrfs_fs_devices *test_fs_devices = data;

	struct btrfs_root *root = btrfs_sb(s);



	/*

	 * If this super block is going away, return false as it

	 * can't match as an existing super block.

	 */

	if (!atomic_read(&s->s_active))

		return 0;

	return root->fs_info->fs_devices == test_fs_devices;

}