[PATCH v3 1/2] mm: zswap: Remove redundant checks in zswap_cpu_comp_dead().

Kanchana P. Sridhar
2026-03-31T18:34:10Z

There are presently redundant checks on the per-CPU acomp_ctx and it's
"req" member in zswap_cpu_comp_dead(): redundant because they are
inconsistent with zswap_pool_create() handling of failure in allocating
the acomp_ctx, and with the expected NULL return value from the
acomp_request_alloc() API when it fails to allocate an acomp_req.

Fix these by converting to them to be NULL checks.

Add comments in zswap_cpu_comp_prepare() clarifying the expected return
values of the crypto_alloc_acomp_node() and acomp_request_alloc() API.

Suggested-by: Yosry Ahmed <yosry@kernel.org>
Signed-off-by: Kanchana P. Sridhar <kanchanapsridhar2026@gmail.com>
Acked-by: Yosry Ahmed <yosry@kernel.org>
---
mm/zswap.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/mm/zswap.c b/mm/zswap.c
index 4f2e652e8ad3..c59045b59ffe 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -749,6 +749,10 @@ static int zswap_cpu_comp_prepare(unsigned int cpu, struct hlist_node *node)
goto fail;
}

+ /*
+ * In case of an error, crypto_alloc_acomp_node() returns an
+ * error pointer, never NULL.
+ */
acomp = crypto_alloc_acomp_node(pool->tfm_name, 0, 0, cpu_to_node(cpu));
if (IS_ERR(acomp)) {
pr_err("could not alloc crypto acomp %s : %pe\n",
@@ -757,6 +761,7 @@ static int zswap_cpu_comp_prepare(unsigned int cpu, struct hlist_node *node)
goto fail;
}

+ /* acomp_request_alloc() returns NULL in case of an error. */
req = acomp_request_alloc(acomp);
if (!req) {
pr_err("could not alloc crypto acomp_request %s\n",
@@ -802,7 +807,7 @@ static int zswap_cpu_comp_dead(unsigned int cpu, struct hlist_node *node)
struct crypto_acomp *acomp;
u8 *buffer;

- if (IS_ERR_OR_NULL(acomp_ctx))
+ if (!acomp_ctx)
return 0;

mutex_lock(&acomp_ctx->mutex);
@@ -817,8 +822,11 @@ static int zswap_cpu_comp_dead(unsigned int cpu, struct hlist_node *node)
/*
* Do the actual freeing after releasing the mutex to avoid subtle
* locking dependencies causing deadlocks.
+ *
+ * If there was an error in allocating @acomp_ctx->req, it
+ * would be set to NULL.
*/
- if (!IS_ERR_OR_NULL(req))
+ if (req)
acomp_request_free(req);
if (!IS_ERR_OR_NULL(acomp))
crypto_free_acomp(acomp);
--
2.39.5