On Fri 10-06-16 16:24:59, Sergey Senozhatsky wrote: > that was fast! > > On (06/10/16 08:34), Michal Hocko wrote: > [..] > > OK, so this is flags & GFP_SLAB_BUG_MASK BUG_ON because gfp is > > ___GFP_HIGHMEM. It is my [1] patch which has introduced it. > > I think we need the following. Andrew could you fold it into > > mm-memcg-use-consistent-gfp-flags-during-readahead.patch or maybe keep > > it as a separate patch? > > > > [1] > > http://lkml.kernel.org/r/[email protected] > > > > Thanks for the report Sergey! > > after quick tests -- works for me. please see below. [...] > so the first bio_alloc() is ok now. what about the second bio_alloc() > in mpage_alloc()? it'll still see the ___GFP_HIGHMEM?
Sure, early morning for me... Thanks for catching that. --- >From a2712312c0a36506ba003747c593dfbdf8eaa8be Mon Sep 17 00:00:00 2001 From: Michal Hocko <[email protected]> Date: Fri, 10 Jun 2016 08:27:33 +0200 Subject: [PATCH] mm: restrict gfp mask in mpage_alloc Sergey has reported that we might hit BUG_ON in new_slab() because unrestricted gfp mask used for the readahead purposes contains incompatible flags (__GFP_HIGHMEM in his case): [ 429.191962] gfp: 2 [ 429.192634] ------------[ cut here ]------------ [ 429.193281] kernel BUG at mm/slub.c:1616! [...] [ 429.217369] [<ffffffff811ca221>] bio_alloc_bioset+0xbd/0x1b1 [ 429.218013] [<ffffffff81148078>] mpage_alloc+0x28/0x7b [ 429.218650] [<ffffffff8114856a>] do_mpage_readpage+0x43d/0x545 [ 429.219282] [<ffffffff81148767>] mpage_readpages+0xf5/0x152 Make sure that mpage_alloc always restricts the mask to GFP_KERNEL subset. This is what was done before "mm, memcg: use consistent gfp flags during readahead" explicitly by mapping_gfp_constraint(mapping, GFP_KERNEL) in mpage_readpages. Reported-by: Sergey Senozhatsky <[email protected]> Signed-off-by: Michal Hocko <[email protected]> --- fs/mpage.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/fs/mpage.c b/fs/mpage.c index 9c11255b0797..c8a05901a37b 100644 --- a/fs/mpage.c +++ b/fs/mpage.c @@ -71,6 +71,8 @@ mpage_alloc(struct block_device *bdev, { struct bio *bio; + /* Restrict the given (page cache) mask for slab allocations */ + gfp_flags &= GFP_KERNEL; bio = bio_alloc(gfp_flags, nr_vecs); if (bio == NULL && (current->flags & PF_MEMALLOC)) { -- 2.8.1 -- Michal Hocko SUSE Labs
