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SubjectRe: [PATCH 3/6] xfs: map KM_MAYFAIL to __GFP_RETRY_MAYFAIL
Christoph, Darrick
could you have a look at this patch please? Andrew has put it into mmotm
but I definitely do not want it passes your attention.

On Fri 23-06-17 10:53:42, Michal Hocko wrote:
> From: Michal Hocko <mhocko@suse.com>
>
> KM_MAYFAIL didn't have any suitable GFP_FOO counterpart until recently
> so it relied on the default page allocator behavior for the given set
> of flags. This means that small allocations actually never failed.
>
> Now that we have __GFP_RETRY_MAYFAIL flag which works independently on the
> allocation request size we can map KM_MAYFAIL to it. The allocator will
> try as hard as it can to fulfill the request but fails eventually if
> the progress cannot be made. It does so without triggering the OOM
> killer which can be seen as an improvement because KM_MAYFAIL users
> should be able to deal with allocation failures.
>
> Cc: Darrick J. Wong <darrick.wong@oracle.com>
> Cc: Christoph Hellwig <hch@infradead.org>
> Signed-off-by: Michal Hocko <mhocko@suse.com>
> ---
> fs/xfs/kmem.h | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/fs/xfs/kmem.h b/fs/xfs/kmem.h
> index d6ea520162b2..4d85992d75b2 100644
> --- a/fs/xfs/kmem.h
> +++ b/fs/xfs/kmem.h
> @@ -54,6 +54,16 @@ kmem_flags_convert(xfs_km_flags_t flags)
> lflags &= ~__GFP_FS;
> }
>
> + /*
> + * Default page/slab allocator behavior is to retry for ever
> + * for small allocations. We can override this behavior by using
> + * __GFP_RETRY_MAYFAIL which will tell the allocator to retry as long
> + * as it is feasible but rather fail than retry forever for all
> + * request sizes.
> + */
> + if (flags & KM_MAYFAIL)
> + lflags |= __GFP_RETRY_MAYFAIL;
> +
> if (flags & KM_ZERO)
> lflags |= __GFP_ZERO;
>
> --
> 2.11.0
>

--
Michal Hocko
SUSE Labs

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