+ mm-zswap-remove-redundant-checks-in-zswap_cpu_comp_dead.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm: zswap: remove redundant checks in zswap_cpu_comp_dead()
has been added to the -mm mm-unstable branch.  Its filename is
     mm-zswap-remove-redundant-checks-in-zswap_cpu_comp_dead.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-zswap-remove-redundant-checks-in-zswap_cpu_comp_dead.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: "Kanchana P. Sridhar" <kanchanapsridhar2026@gmail.com>
Subject: mm: zswap: remove redundant checks in zswap_cpu_comp_dead()
Date: Tue, 31 Mar 2026 11:33:50 -0700

Patch series "zswap pool per-CPU acomp_ctx simplifications", v3.

This patchset first removes redundant checks on the acomp_ctx and its
"req" member in zswap_cpu_comp_dead().

Next, it persists the zswap pool's per-CPU acomp_ctx resources to last
until the pool is destroyed.  It then simplifies the per-CPU acomp_ctx
mutex locking in zswap_compress()/zswap_decompress().

Code comments added after allocation and before checking to deallocate the
per-CPU acomp_ctx's members, based on expected crypto API return values
and zswap changes this patchset makes.

Patch 2 is an independent submission of patch 23 from [1], to
facilitate merging.


This patch (of 2):

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.

Link: https://lkml.kernel.org/r/20260331183351.29844-2-kanchanapsridhar2026@gmail.com
Link: https://patchwork.kernel.org/project/linux-mm/list/?series=1046677
Signed-off-by: Kanchana P. Sridhar <kanchanapsridhar2026@gmail.com>
Suggested-by: Yosry Ahmed <yosry@kernel.org>
Acked-by: Yosry Ahmed <yosry@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/zswap.c |   12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

--- a/mm/zswap.c~mm-zswap-remove-redundant-checks-in-zswap_cpu_comp_dead
+++ a/mm/zswap.c
@@ -749,6 +749,10 @@ static int zswap_cpu_comp_prepare(unsign
 		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(unsign
 		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
 	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
 	/*
 	 * 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);
_

Patches currently in -mm which might be from kanchanapsridhar2026@gmail.com are

mm-zswap-remove-redundant-checks-in-zswap_cpu_comp_dead.patch
mm-zswap-tie-per-cpu-acomp_ctx-lifetime-to-the-pool.patch