From 7310895779624a11153d74a2132f01be6e360b7c Mon Sep 17 00:00:00 2001
From: Johannes Weiner <hannes@cmpxchg.org>
Date: Thu, 27 Jul 2023 12:22:24 -0400
Subject: [PATCH] mm: zswap: tighten up entry invalidation
Removing a zswap entry from the tree is tied to an explicit operation
that's supposed to drop the base reference: swap invalidation, exclusive
load, duplicate store. Don't silently remove the entry on final put, but
instead warn if an entry is in tree without reference.
While in that diff context, convert a BUG_ON to a WARN_ON_ONCE. No need
to crash on a refcount underflow.
Link: https://lkml.kernel.org/r/20230727162343.1415598-3-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Yosry Ahmed <yosryahmed@google.com>
Cc: Barry Song <song.bao.hua@hisilicon.com>
Cc: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
mm/zswap.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/mm/zswap.c b/mm/zswap.c
index 93707a1799b8a..ea921b25c245b 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -417,9 +417,9 @@ static void zswap_entry_put(struct zswap_tree *tree,
{
int refcount = --entry->refcount;
- BUG_ON(refcount < 0);
+ WARN_ON_ONCE(refcount < 0);
if (refcount == 0) {
- zswap_rb_erase(&tree->rbroot, entry);
+ WARN_ON_ONCE(!RB_EMPTY_NODE(&entry->rbnode));
zswap_free_entry(entry);
}
}
--
2.30.2