Re: [PATCH] Revert "kmemleak: allow to coexist with fault injection"

[Michal Hocko]

On Wed 17-07-19 01:50:31, Yang Shi wrote:
> When running ltp's oom test with kmemleak enabled, the below warning was
> triggerred since kernel detects __GFP_NOFAIL & ~__GFP_DIRECT_RECLAIM is
> passed in:
> 
> WARNING: CPU: 105 PID: 2138 at mm/page_alloc.c:4608 __alloc_pages_nodemask+0x1c31/0x1d50
> Modules linked in: loop dax_pmem dax_pmem_core ip_tables x_tables xfs virtio_net net_failover virtio_blk failover ata_generic virtio_pci virtio_ring virtio libata
> CPU: 105 PID: 2138 Comm: oom01 Not tainted 5.2.0-next-20190710+ #7
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.10.2-0-g5f4c7b1-prebuilt.qemu-project.org 04/01/2014
> RIP: 0010:__alloc_pages_nodemask+0x1c31/0x1d50
> ...
>  kmemleak_alloc+0x4e/0xb0
>  kmem_cache_alloc+0x2a7/0x3e0
>  ? __kmalloc+0x1d6/0x470
>  ? ___might_sleep+0x9c/0x170
>  ? mempool_alloc+0x2b0/0x2b0
>  mempool_alloc_slab+0x2d/0x40
>  mempool_alloc+0x118/0x2b0
>  ? __kasan_check_read+0x11/0x20
>  ? mempool_resize+0x390/0x390
>  ? lock_downgrade+0x3c0/0x3c0
>  bio_alloc_bioset+0x19d/0x350
>  ? __swap_duplicate+0x161/0x240
>  ? bvec_alloc+0x1b0/0x1b0
>  ? do_raw_spin_unlock+0xa8/0x140
>  ? _raw_spin_unlock+0x27/0x40
>  get_swap_bio+0x80/0x230
>  ? __x64_sys_madvise+0x50/0x50
>  ? end_swap_bio_read+0x310/0x310
>  ? __kasan_check_read+0x11/0x20
>  ? check_chain_key+0x24e/0x300
>  ? bdev_write_page+0x55/0x130
>  __swap_writepage+0x5ff/0xb20
> 
> The mempool_alloc_slab() clears __GFP_DIRECT_RECLAIM, however kmemleak has
> __GFP_NOFAIL set all the time due to commit
> d9570ee3bd1d4f20ce63485f5ef05663866fe6c0 ("kmemleak: allow to coexist
> with fault injection").  But, it doesn't make any sense to have
> __GFP_NOFAIL and ~__GFP_DIRECT_RECLAIM specified at the same time.
> 
> According to the discussion on the mailing list, the commit should be
> reverted for short term solution.  Catalin Marinas would follow up with a better
> solution for longer term.
> 
> The failure rate of kmemleak metadata allocation may increase in some
> circumstances, but this should be expected side effect.
> 
> Suggested-by: Catalin Marinas <catalin.marinas@xxxxxxx>
> Cc: Michal Hocko <mhocko@xxxxxxxx>
> Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
> Cc: David Rientjes <rientjes@xxxxxxxxxx>
> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
> Cc: Qian Cai <cai@xxxxxx>
> Signed-off-by: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx>

I forgot
Acked-by: Michal Hocko <mhocko@xxxxxxxx>

> ---
>  mm/kmemleak.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/kmemleak.c b/mm/kmemleak.c
> index 9dd581d..884a5e3 100644
> --- a/mm/kmemleak.c
> +++ b/mm/kmemleak.c
> @@ -114,7 +114,7 @@
>  /* GFP bitmask for kmemleak internal allocations */
>  #define gfp_kmemleak_mask(gfp)	(((gfp) & (GFP_KERNEL | GFP_ATOMIC)) | \
>  				 __GFP_NORETRY | __GFP_NOMEMALLOC | \
> -				 __GFP_NOWARN | __GFP_NOFAIL)
> +				 __GFP_NOWARN)
>  
>  /* scanning area inside a memory block */
>  struct kmemleak_scan_area {
> -- 
> 1.8.3.1

-- 
Michal Hocko
SUSE Labs