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Subject[PATCH 3.12 125/144] GFS2: dont hold s_umount over blkdev_put
Date
3.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Steven Whitehouse <swhiteho@redhat.com>

commit dfe5b9ad83a63180f358b27d1018649a27b394a9 upstream.

This is a GFS2 version of Tejun's patch:
4f331f01b9c43bf001d3ffee578a97a1e0633eac
vfs: don't hold s_umount over close_bdev_exclusive() call

In this case its blkdev_put itself that is the issue and this
patch uses the same solution of dropping and retaking s_umount.

Reported-by: Tejun Heo <tj@kernel.org>
Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/gfs2/ops_fstype.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)

--- a/fs/gfs2/ops_fstype.c
+++ b/fs/gfs2/ops_fstype.c
@@ -1366,8 +1366,18 @@ static struct dentry *gfs2_mount(struct
if (IS_ERR(s))
goto error_bdev;

- if (s->s_root)
+ if (s->s_root) {
+ /*
+ * s_umount nests inside bd_mutex during
+ * __invalidate_device(). blkdev_put() acquires
+ * bd_mutex and can't be called under s_umount. Drop
+ * s_umount temporarily. This is safe as we're
+ * holding an active reference.
+ */
+ up_write(&s->s_umount);
blkdev_put(bdev, mode);
+ down_write(&s->s_umount);
+ }

memset(&args, 0, sizeof(args));
args.ar_quota = GFS2_QUOTA_DEFAULT;



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