[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Message-ID: <20150911082726.GC3417@dhcp22.suse.cz>
Date: Fri, 11 Sep 2015 10:27:27 +0200
From: Michal Hocko <mhocko@...nel.org>
To: Vlastimil Babka <vbabka@...e.cz>
Cc: Chris Mason <clm@...com>, linux-btrfs@...r.kernel.org,
Josef Bacik <jbacik@...com>, David Sterba <dsterba@...e.cz>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] btrfs: fortification for GFP_NOFS allocations
On Wed 09-09-15 18:13:39, Vlastimil Babka wrote:
> On 08/19/2015 08:17 PM, Chris Mason wrote:
> >On Wed, Aug 19, 2015 at 02:17:39PM +0200, mhocko@...nel.org wrote:
> >>Hi,
> >>these two patches were sent as a part of a larger RFC which aims at
> >>allowing GFP_NOFS allocations to fail to help sort out memory reclaim
> >>issues bound to the current behavior
> >>(http://marc.info/?l=linux-mm&m=143876830616538&w=2).
> >>
> >>It is clear that move to the GFP_NOFS behavior change is a long term
> >>plan but these patches should be good enough even with that change in
> >>place. It also seems that Chris wasn't opposed and would be willing to
> >>take them http://marc.info/?l=linux-mm&m=143991792427165&w=2 so here we
> >>come. I have rephrased the changeslogs to not refer to the patch which
> >>changes the NOFS behavior.
> >>
> >>Just to clarify. These two patches allowed my particular testcase
> >>(mentioned in the cover referenced above) to survive it doesn't mean
> >>that the failing GFP_NOFS are OK now. I have seen some other places
> >>where GFP_NOFS allocation is followed by BUG_ON(ALLOC_FAILED). I have
> >>not encountered them though.
> >>
> >>Let me know if you would prefer other changes.
> >
> >My plan is to start with these two and take more as required.
>
> I've previously noticed in __set_extent_bit() things like:
>
> if (!prealloc && (mask & __GFP_WAIT)) {
> prealloc = alloc_extent_state(mask);
> BUG_ON(!prealloc);
> }
>
> and later:
>
> prealloc = alloc_extent_state_atomic(prealloc);
> BUG_ON(!prealloc);
Yes. I have noticed also many other places:
$ git grep "BUG_ON.*ENOMEM" -- fs/btrfs/ | wc -l
47
I have talked to David Sterba and he said this is on his todo list.
So this will likely take some more time but it is definitely good to
sort out.
--
Michal Hocko
SUSE Labs
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists