[ Upstream commit 2298abcbe1 ]
When cache cleanup runs concurrently with cache entry removal, a race
condition can occur that leads to incorrect nextcheck times. This can
delay cache cleanup for the cache_detail by up to 1800 seconds:
1. cache_clean() sets nextcheck to current time plus 1800 seconds
2. While scanning a non-empty bucket, concurrent cache entry removal can
empty that bucket
3. cache_clean() finds no cache entries in the now-empty bucket to update
the nextcheck time
4. This maybe delays the next scan of the cache_detail by up to 1800
seconds even when it should be scanned earlier based on remaining
entries
Fix this by moving the hash_lock acquisition earlier in cache_clean().
This ensures bucket emptiness checks and nextcheck updates happen
atomically, preventing the race between cleanup and entry removal.
Signed-off-by: Long Li <leo.lilong@huawei.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
05aba2d316