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Subject[PATCH] Revert "kmemleak: allow to coexist with fault injection"
Date
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@arm.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Qian Cai <cai@lca.pw>
Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
---
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
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