Re: [PATCH 1/2 v2] bcachefs: do not use PF_MEMALLOC_NORECLAIM

Dave Chinner
2024-08-28T04:10:05Z

On Tue, Aug 27, 2024 at 08:15:43AM +0200, Michal Hocko wrote:
> From: Michal Hocko <mhocko@suse.com>
>
> bch2_new_inode relies on PF_MEMALLOC_NORECLAIM to try to allocate a new
> inode to achieve GFP_NOWAIT semantic while holding locks. If this
> allocation fails it will drop locks and use GFP_NOFS allocation context.
>
> We would like to drop PF_MEMALLOC_NORECLAIM because it is really
> dangerous to use if the caller doesn't control the full call chain with
> this flag set. E.g. if any of the function down the chain needed
> GFP_NOFAIL request the PF_MEMALLOC_NORECLAIM would override this and
> cause unexpected failure.
>
> While this is not the case in this particular case using the scoped gfp
> semantic is not really needed bacause we can easily pus the allocation
> context down the chain without too much clutter.
>
> Acked-by: Christoph Hellwig <hch@lst.de>
> Signed-off-by: Michal Hocko <mhocko@suse.com>

Looks good to me.

Reviewed-by: Dave Chinner <dchinner@redhat.com>

--
Dave Chinner
david@fromorbit.com