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mm/zswap: don't return LRU_SKIP if we have dropped lru lock 

LRU_SKIP can only be returned if we don't ever dropped lru lock, or we
need to return LRU_RETRY to restart from the head of lru list.

Otherwise, the iteration might continue from a cursor position that was
freed while the locks were dropped.

Actually we may need to introduce another LRU_STOP to really terminate the
ongoing shrinking scan process, when we encounter a warm page already in
the swap cache.  The current list_lru implementation doesn't have this
function to early break from __list_lru_walk_one.

Link: https://lkml.kernel.org/r/20240126-zswap-writeback-race-v2-1-b10479847099@bytedance.com
Fixes: b5ba474f3f ("zswap: shrink zswap pool based on memory pressure")
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Cc: Chris Li <chriscli@google.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Chengming Zhou 2024-01-28 13:28:49 +00:00 committed by Andrew Morton
parent 79d72c68c5
commit 27d3969b47
1 changed files with 1 additions and 3 deletions
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4
mm/zswap.c
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@ -895,10 +895,8 @@ static enum lru_status shrink_memcg_cb(struct list_head *item, struct list_lru_o
* into the warmer region. We should terminate shrinking (if we're in the dynamic
* shrinker context).
*/
if (writeback_result == -EEXIST && encountered_page_in_swapcache) {
ret = LRU_SKIP;
if (writeback_result == -EEXIST && encountered_page_in_swapcache)
*encountered_page_in_swapcache = true;
}
goto put_unlock;
}