From: Minchan Kim minchan@kernel.org Subject: mm: fs: fix lru_cache_disabled race in bh_lru
Check lru_cache_disabled under bh_lru_lock. Otherwise, it could introduce race below and it fails to migrate pages containing buffer_head.
CPU 0 CPU 1
bh_lru_install lru_cache_disable lru_cache_disabled = false atomic_inc(&lru_disable_count); invalidate_bh_lrus_cpu of CPU 0 bh_lru_lock __invalidate_bh_lrus bh_lru_unlock bh_lru_lock install the bh bh_lru_unlock
WHen this race happens a CMA allocation fails, which is critical for the workload which depends on CMA.
Link: https://lkml.kernel.org/r/20220308180709.2017638-1-minchan@kernel.org Fixes: 8cc621d2f45d ("mm: fs: invalidate BH LRU during page migration") Signed-off-by: Minchan Kim minchan@kernel.org Cc: Chris Goldsworthy cgoldswo@codeaurora.org Cc: Marcelo Tosatti mtosatti@redhat.com Cc: John Dias joaodias@google.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
fs/buffer.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)
--- a/fs/buffer.c~mm-fs-fix-lru_cache_disabled-race-in-bh_lru +++ a/fs/buffer.c @@ -1235,16 +1235,18 @@ static void bh_lru_install(struct buffer int i;
check_irqs_on(); + bh_lru_lock(); + /* * the refcount of buffer_head in bh_lru prevents dropping the * attached page(i.e., try_to_free_buffers) so it could cause * failing page migration. * Skip putting upcoming bh into bh_lru until migration is done. */ - if (lru_cache_disabled()) + if (lru_cache_disabled()) { + bh_lru_unlock(); return; - - bh_lru_lock(); + }
b = this_cpu_ptr(&bh_lrus); for (i = 0; i < BH_LRU_SIZE; i++) { _