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authorIan Kent <raven@themaw.net>2010-11-22 02:21:38 +0000
committerChris Mason <chris.mason@oracle.com>2010-11-27 13:37:44 -0500
commit619c8c763928841b1112e1d417f88bc1d44daecb (patch)
tree23fc73cf043faac2cdb15a0b22e6e9e29a69797a
parentbc1cbf1f86aa2501efa9ca637c736fce6bcc4b1d (diff)
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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>
-rw-r--r--fs/btrfs/super.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 66e4612a791..141fb317d3b 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -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;
}