On 02/25/2016 11:08 AM, Michal Hocko wrote: > On Thu 25-02-16 11:01:32, Nikolay Borisov wrote: >> >> >> 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. > > This is not true. GFP_NOFAIL should be used where the allocation failure > is no tolleratable and it is much more preferrable to doing an opencoded > endless loop over page allocator. In that case the comments in buffered_rmqueue, and the WARN_ON in __alloc_pages_may_oom and __alloc_pages_slowpath perhaps should be removed since they are misleading? > >> 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? > > I have posted a similar patch last year: > http://lkml.kernel.org/r/1438768284-30927-6-git-send-email-mhocko@xxxxxxxxxx > because I could see emergency reboots when GFP_NOFS allocations were > allowed to fail. > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>