Re: [PATCH RFC] ext4: use __GFP_NOFAIL in ext4_free_blocks()

From: Nikolay Borisov
Date: Thu Feb 25 2016 - 04:01:41 EST

On 02/24/2016 07:09 PM, Konstantin Khlebnikov wrote:
> This might be unexpected but pages allocated for sbi->s_buddy_cache are
> charged to current memory cgroup. So, GFP_NOFS allocation could fail if
> current task has been killed by OOM or if current memory cgroup has no
> free memory left. Block allocator cannot handle such failures here yet.
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>

Adding new users of GFP_NOFAIL is deprecated. Where exactly does the
block allocator fail, I skimmed the code and failing ext4_mb_load_buddy
seems to be handled at all call sites. There are some BUG_ONs but from
the comments there I guess they should occur when we try to find a page
and not allocate a new one?