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SubjectRe: [PATCH] deadlock with suspend and quotas


On Tue, 3 Jan 2012, Al Viro wrote:

> On Fri, Nov 25, 2011 at 03:25:16PM -0500, Mikulas Patocka wrote:
>
> > The following patch fixes the deadlock. When the quota subsystem takes s_umount,
> > it checks if the filesystem is frozen. If it is, we drop s_umount, wait for
> > the filesystem to resume and retry.
> >
> > Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
> > CC: stable@kernel.org
>
> So basically you want a variant of get_super() that would get you a
> superblock for this bdev, locked and unfrozen? Fair enough, but
> * that should be a proper helper in super.c, rather than
> open-coded in fs/quota/quota.c, of all places
> * what about other existing callers get_super() and its friends?

Hi

You can look at that functionality here: I've already made a patch that
has it:
https://www.redhat.com/archives/dm-devel/2011-November/msg00151.html

Basically, the patch introduces a function down_read_s_umount, which takes
s_umount for read, but makes sure that the filesystem is not frozen. Then,
it adds a boolean parameter to get_super() which tells get_super() that it
should wait for unfreeze (i.e. call "down_read_s_umount" isntead of
"down_read(&sb->s_umount)").

Mikulas

> and while we are at it, why in damnation name is it exported? The only
> caller outside of core VFS is under #if 0...
>


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