tree e73070fcad99b800f0324992c392d44c6dddc97c
parent 4fadd7bb20a1e7c774ed88dc703d8fbcd00ff917
author Christoph Hellwig <hch@lst.de> 1249334915 +0200
committer Al Viro <viro@zeniv.linux.org.uk> 1253792861 -0400

freeze_bdev: grab active reference to frozen superblocks

Currently we held s_umount while a filesystem is frozen, despite that we
might return to userspace and unlock it from a different process.  Instead
grab an active reference to keep the file system busy and add an explicit
check for frozen filesystems in remount and reject the remount instead
of blocking on s_umount.

Add a new get_active_super helper to super.c for use by freeze_bdev that
grabs an active reference to a superblock from a given block device.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>