Re: [PATCH 3/5] ext4: ext4_mark_recovery_complete() doesn't need to use lock_super

[Christoph Hellwig <hch@infradead.org>]

On Sat, Apr 25, 2009 at 11:49:23PM -0400, Theodore Ts'o wrote:
> The function ext4_mark_recovery_complete() is called from two call
> paths: either (a) while mounting the filesystem, in which case there's
> no danger of any other CPU calling write_super() until the mount is
> completed, and (b) while remounting the filesystem read-write, in
> which case the fs core has already locked the superblock, and in any
> case write_super() wouldn't be called until the filesystem is
> successfully changed from being mounted read-only to read-write.

Currently ext4_remount releases/reqacquires lock_super around
ext4_mark_recovery_complete, and unfortunately currently ->write_super
can be called on a r/o filesystem (that's why we have the MS_RDONLY
checks in all instance, I plan to clean that mess up).

So for now I would keep that instance of lock_super, it'll also serve as
documentation for the locking requirements once we pushed down
lock_super to the filesystem in ->write_super and ->remount_fs so that
it can eventually be replaced with an ext4-local lock.