diff mbox series

[v3,1/4] mm: zswap: always shrink in zswap_store() if zswap_pool_reached_full

Message ID 20240413022407.785696-2-yosryahmed@google.com (mailing list archive)
State New
Headers show
Series zswap same-filled and limit checking cleanups | expand

Commit Message

Yosry Ahmed April 13, 2024, 2:24 a.m. UTC 
The cleanup code in zswap_store() is not pretty, particularly the
'shrink' label at the bottom that ends up jumping between cleanup
labels.

Instead of having a dedicated label to shrink the pool, just use
zswap_pool_reached_full directly to figure out if the pool needs
shrinking. zswap_pool_reached_full should be true if and only if the
pool needs shrinking.

The only caveat is that the value of zswap_pool_reached_full may be
changed by concurrent zswap_store() calls between checking the limit and
testing zswap_pool_reached_full in the cleanup code. This is fine
because:
- If zswap_pool_reached_full was true during limit checking then became
  false during the cleanup code, then someone else already took care of
  shrinking the pool and there is no need to queue the worker. That
  would be a good change.
- If zswap_pool_reached_full was false during limit checking then became
  true during the cleanup code, then someone else hit the limit
  meanwhile. In this case, both threads will try to queue the worker,
  but it never gets queued more than once anyway. Also, calling
  queue_work() multiple times when the limit is hit could already happen
  today, so this isn't a significant change in any way.

Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
---
 mm/zswap.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)
diff mbox series

Patch

diff --git a/mm/zswap.c b/mm/zswap.c
index 741957f36f38b..77b6bb2099763 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -1429,12 +1429,12 @@  bool zswap_store(struct folio *folio)
 	if (cur_pages >= max_pages) {
 		zswap_pool_limit_hit++;
 		zswap_pool_reached_full = true;
-		goto shrink;
+		goto reject;
 	}
 
 	if (zswap_pool_reached_full) {
 		if (cur_pages > zswap_accept_thr_pages())
-			goto shrink;
+			goto reject;
 		else
 			zswap_pool_reached_full = false;
 	}
@@ -1540,6 +1540,8 @@  bool zswap_store(struct folio *folio)
 	zswap_entry_cache_free(entry);
 reject:
 	obj_cgroup_put(objcg);
+	if (zswap_pool_reached_full)
+		queue_work(shrink_wq, &zswap_shrink_work);
 check_old:
 	/*
 	 * If the zswap store fails or zswap is disabled, we must invalidate the
@@ -1550,10 +1552,6 @@  bool zswap_store(struct folio *folio)
 	if (entry)
 		zswap_entry_free(entry);
 	return false;
-
-shrink:
-	queue_work(shrink_wq, &zswap_shrink_work);
-	goto reject;
 }
 
 bool zswap_load(struct folio *folio)