lkml.org 
[lkml]   [2016]   [Jun]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [mmots-2016-06-09-16-49] kernel BUG at mm/slub.c:1616
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/1465301556-26431-1-git-send-email-mhocko@kernel.org
>
> Thanks for the report Sergey!

after quick tests -- works for me. please see below.

> 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 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 <sergey.senozhatsky.work@gmail.com>
> Signed-off-by: Michal Hocko <mhocko@suse.com>
> ---
> fs/mpage.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/mpage.c b/fs/mpage.c
> index 9c11255b0797..5ce75b2e60d1 100644
> --- a/fs/mpage.c
> +++ b/fs/mpage.c
> @@ -71,7 +71,7 @@ mpage_alloc(struct block_device *bdev,
> {
> struct bio *bio;
>
> - bio = bio_alloc(gfp_flags, nr_vecs);
> + bio = bio_alloc(gfp_flags & GFP_KERNEL, nr_vecs);
>
> if (bio == NULL && (current->flags & PF_MEMALLOC)) {
> while (!bio && (nr_vecs /= 2))

so the first bio_alloc() is ok now. what about the second bio_alloc()
in mpage_alloc()? it'll still see the ___GFP_HIGHMEM?

may be something like this (composed in mail client)

static struct bio *
mpage_alloc(struct block_device *bdev,
sector_t first_sector, int nr_vecs,
gfp_t gfp_flags)
{
struct bio *bio;

+ gfp_flags &= GFP_KERNEL;

- bio = bio_alloc(gfp_flags, nr_vecs);
+ bio = bio_alloc(gfp_flags & GFP_KERNEL, nr_vecs);

if (bio == NULL && (current->flags & PF_MEMALLOC)) {
while (!bio && (nr_vecs /= 2))
bio = bio_alloc(gfp_flags, nr_vecs);
^^^^^^^^^^^^^^^^^^^^ BUG?
}

if (bio) {
bio->bi_bdev = bdev;
bio->bi_iter.bi_sector = first_sector;
}
return bio;
}


=====

the second part of the original report (sleeping function called from
invalid context at include/linux/sched.h:2960) is unrelated, I'll fork
a new thread; seems that it's coming from a380a3c755, Christoph Lameter,
2015-11-20.

-ss

\
 
 \ /
  Last update: 2016-06-10 09:41    [W:0.089 / U:0.580 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site