Ocfs2 devel - Mar 2012 - ext3/4, btrfs, ocfs2: How to assure that cleancache_invalidate_fs is called on every superblock free

Hello,

Is it ever possible for a superblock for a mounted filesystem to be
free'd without a previous call to unmount the filesystem?
I need to be certain that the function cleancache_invalidate_fs, which
is at the moment called by deactivate_locked_super (fs/super.c) [1],
is called before every free on a superblock of cleancache-enabled
filesystems.
Is this already the case or are there situations in which this does not happen?

It would be interesting to know this, as we are planning to have
cleancache save pointers to superblocks of every mounted
cleancache-enabled filesystem [2] and it would be fatal if a
superblock is free'd without cleancache being notified.

Regards
Andor

[1] commit c515e1fd361c2a08a9c2eb139396ec30a4f477dc
[2] http://marc.info/?l=linux-mm&m=133122649732669&w=2

Hello,

On Fri 09-03-12 14:40:22, Andor Daam wrote:
> Is it ever possible for a superblock for a mounted filesystem to be
> free'd without a previous call to unmount the filesystem?
  No, I don't think so (well, except for cases where we do not manage to
fully setup the superblock). But be aware that mount/umount need not be
really the entry points you are looking for since filesystem can be mounted
several times. Rather deactivate_locked_supers() is the place you are
looking for...
> I need to be certain that the function cleancache_invalidate_fs, which is
> at the moment called by deactivate_locked_super (fs/super.c) [1], is
> called before every free on a superblock of cleancache-enabled
> filesystems.  Is this already the case or are there situations in which
> this does not happen?
> 
> It would be interesting to know this, as we are planning to have
> cleancache save pointers to superblocks of every mounted
> cleancache-enabled filesystem [2] and it would be fatal if a
> superblock is free'd without cleancache being notified.
								Honza
-- 
Jan Kara <jack at suse.cz>
SUSE Labs, CR