lkml.org 
[lkml]   [2006]   [Jul]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [BUG?] possible recursive locking detected
Anton Altaparmakov wrote:
> On Thu, 2006-07-27 at 00:38 -0700, Andrew Morton wrote:
>
>>On Thu, 27 Jul 2006 08:15:27 +0100
>>Anton Altaparmakov <aia21@cam.ac.uk> wrote:
>>
>>
>>>>I'm surprised ext2 is allocating with __GFP_FS set, though. Would that
>>>>cause any problem?
>>>
>>>That is an ext2 bug IMO.
>>
>>There is no bug.
>>
>>What there is is an ill-defined set of rules. If we want to tighten these
>>rules we have a choice between
>
>
> I beg to differ. It is a bug. You cannot reenter the file system when
> the file system is trying to allocate memory. Otherwise you can never
> allocate memory with any locks held or you are bound to introduce an
> A->B B->A deadlock somewhere.

I don't think it is a bug in general. It really depends on the allocation:

- If it is a path that might be required in order to writeout a page, then
yes GFP_NOFS is going to help prevent deadlocks.

- If it is a path where you'll take the same locks as page reclaim requires,
then again GFP_NOFS is required.

For NTFS case, it seems like holding i_mutex on the write path falls foul
of the second problem. But I agree with Andrew that this is a critical case
where we do have to enter the fs. GFP_NOFS is too big a hammer to use.

I guess you'd have to change NTFS to do something sane privately, or come
up with a nice general solution that doesn't harm the common filesystems
that apparently don't have a problem here... can you just add GFP_NOFS to
NTFS's mapping_gfp_mask to start with?

--
SUSE Labs, Novell Inc.
Send instant messages to your online friends http://au.messenger.yahoo.com

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2006-07-27 11:21    [W:0.061 / U:0.828 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site