mm/slub: prevent pfmemalloc objects from entering the barn

kmem_cache_return_sheaf() may refill a partially consumed sheaf before
placing it in the barn. Without an explicit restriction, this refill may
draw objects from pfmemalloc slabs and consume emergency reserves.

Add __GFP_NOMEMALLOC so that returned sheaves are refilled only from
non-pfmemalloc slabs. Also add __GFP_NOWARN, as suggested by Hao Li,
because this refill is a best-effort attempt and failure is acceptable.
If the refill fails, flush and free the sheaf instead.

Fixes: 1ce20c28eafd ("slab: handle pfmemalloc slabs properly with sheaves")
Cc: stable@vger.kernel.org
Signed-off-by: Shengming Hu <hu.shengming@zte.com.cn>
Reviewed-by: Harry Yoo (Oracle) <harry@kernel.org>
Reviewed-by: Hao Li <hao.li@linux.dev>
Link: https://patch.msgid.link/20260721084522552ZPa16p1SRj3PYat3sqxuN@zte.com.cn
Signed-off-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>

0 files changed, 0 insertions, 0 deletions