diff options
| author | Hao Li <hao.li@linux.dev> | 2026-02-26 19:51:37 +0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2026-03-19 16:08:39 +0100 |
| commit | 146691daf293c5781a75e408043ee8891e60ae4a (patch) | |
| tree | 43ec7b4b92fda3bab8e1acef6b7c67e129acad43 | |
| parent | 159aebd20e0e98acb2fedeceb6a27d97cb6a86a0 (diff) | |
memcg: fix slab accounting in refill_obj_stock() trylock path
commit dccd5ee2625d50239510bcd73ed78559005e00a3 upstream.
In the trylock path of refill_obj_stock(), mod_objcg_mlstate() should use
the real alloc/free bytes (i.e., nr_acct) for accounting, rather than
nr_bytes.
The user-visible impact is that the NR_SLAB_RECLAIMABLE_B and
NR_SLAB_UNRECLAIMABLE_B stats can end up being incorrect.
For example, if a user allocates a 6144-byte object, then before this
fix efill_obj_stock() calls mod_objcg_mlstate(..., nr_bytes=2048), even
though it should account for 6144 bytes (i.e., nr_acct).
When the user later frees the same object with kfree(),
refill_obj_stock() calls mod_objcg_mlstate(..., nr_bytes=6144). This
ends up adding 6144 to the stats, but it should be applying -6144
(i.e., nr_acct) since the object is being freed.
Link: https://lkml.kernel.org/r/20260226115145.62903-1-hao.li@linux.dev
Fixes: 200577f69f29 ("memcg: objcg stock trylock without irq disabling")
Signed-off-by: Hao Li <hao.li@linux.dev>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Vlastimil Babka <vbabka@suse.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | mm/memcontrol.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index ab25d540f0b8..61cf6af26f3c 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -3028,7 +3028,7 @@ static void refill_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes, if (!local_trylock(&obj_stock.lock)) { if (pgdat) - mod_objcg_mlstate(objcg, pgdat, idx, nr_bytes); + mod_objcg_mlstate(objcg, pgdat, idx, nr_acct); nr_pages = nr_bytes >> PAGE_SHIFT; nr_bytes = nr_bytes & (PAGE_SIZE - 1); atomic_add(nr_bytes, &objcg->nr_charged_bytes); |