• Johannes Weiner's avatar
    fs: buffer: move allocation failure loop into the allocator · 84235de3
    Johannes Weiner authored
    Buffer allocation has a very crude indefinite loop around waking the
    flusher threads and performing global NOFS direct reclaim because it can
    not handle allocation failures.
    
    The most immediate problem with this is that the allocation may fail due
    to a memory cgroup limit, where flushers + direct reclaim might not make
    any progress towards resolving the situation at all.  Because unlike the
    global case, a memory cgroup may not have any cache at all, only
    anonymous pages but no swap.  This situation will lead to a reclaim
    livelock with insane IO from waking the flushers and thrashing unrelated
    filesystem cache in a tight loop.
    
    Use __GFP_NOFAIL allocations for buffers for now.  This makes sure that
    any looping happens in the page allocator, which knows how to
    orchestrate kswapd, direct reclaim, and the flushers sensibly.  It also
    allows memory cgroups to detect allocations that can't handle failure
    and will allow them to ultimately bypass the limit if reclaim can not
    make progress.
    Reported-by: 's avatarazurIt <azurit@pobox.sk>
    Signed-off-by: 's avatarJohannes Weiner <hannes@cmpxchg.org>
    Cc: Michal Hocko <mhocko@suse.cz>
    Cc: <stable@kernel.org>
    Signed-off-by: 's avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: 's avatarLinus Torvalds <torvalds@linux-foundation.org>
    84235de3
buffer.c 88.7 KB