Re: [PATCH] mm, vmscan: Do not wait for page writeback for GFP_NOFS allocations

[Rik van Riel]

On 07/01/2015 09:37 AM, Michal Hocko wrote:

> Fix this issue by limiting the wait to reclaim triggered by __GFP_FS
> allocations to make sure we are not called from filesystem paths which
> might be doing exactly this kind of IO optimizations. The page fault
> path, which is the only path that triggers memcg oom killer since 3.12,
> shouldn't require GFP_NOFS and so we shouldn't reintroduce the premature
> OOM killer issue which was originally addressed by the heuristic.
> 
> As per David Chinner the xfs is doing similar thing since 2.6.15 already
> so ext4 is not the only affected filesystem. Moreover he notes:
> : For example: IO completion might require unwritten extent conversion
> : which executes filesystem transactions and GFP_NOFS allocations. The
> : writeback flag on the pages can not be cleared until unwritten
> : extent conversion completes. Hence memory reclaim cannot wait on
> : page writeback to complete in GFP_NOFS context because it is not
> : safe to do so, memcg reclaim or otherwise.

I remember fixing something like this back in the 2.2
days. Funny how these bugs keep coming back.

> Cc: stable # 3.6+
> Fixes: c3b94f44fcb0 ("memcg: further prevent OOM with too many dirty pages")
> Reported-by: Nikolay Borisov <kernel@xxxxxxxx>
> Signed-off-by: Michal Hocko <mhocko@xxxxxxx>

Reviewed-by: Rik van Riel <riel@xxxxxxxxxx>

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