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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: Ian Kent <raven@themaw.net>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
This commit is contained in:
Ian Kent 2010-11-22 02:21:38 +00:00 committed by Chris Mason
parent bc1cbf1f86
commit 619c8c7639
1 changed files with 6 additions and 0 deletions
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6
fs/btrfs/super.c
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@ -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;
}