linux-kernel - Re: [PATCH v4] mm/zswap: store <PAGE_SIZE compression failed page as-is

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Message-Id: <20250821161750.78192-1-sj@kernel.org>
Date: Thu, 21 Aug 2025 09:17:50 -0700
From: SeongJae Park <sj@...nel.org>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: SeongJae Park <sj@...nel.org>,
	Chengming Zhou <chengming.zhou@...ux.dev>,
	Johannes Weiner <hannes@...xchg.org>,
	Nhat Pham <nphamcs@...il.com>,
	Yosry Ahmed <yosry.ahmed@...ux.dev>,
	kernel-team@...a.com,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	Takero Funaki <flintglass@...il.com>,
	David Hildenbrand <david@...hat.com>,
	Baoquan He <bhe@...hat.com>,
	Barry Song <baohua@...nel.org>,
	Chris Li <chrisl@...nel.org>,
	Kairui Song <kasong@...cent.com>,
	kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v4] mm/zswap: store <PAGE_SIZE compression failed page as-is

On Tue, 19 Aug 2025 12:34:04 -0700 SeongJae Park <sj@...nel.org> wrote:

[...]
> Knowing how many compression failures from the crypto engine happened so
> far, and how many incompressible pages are stored at the given moment
> will be useful for future investigations.  Add two new debugfs files,
> crypto_compress_fail and stored_incompressible_pages, for the two
> counts, respectively.
[...]
> diff --git a/mm/zswap.c b/mm/zswap.c
> index 3c0fd8a13718..1f1ac043a2d9 100644
> --- a/mm/zswap.c
> +++ b/mm/zswap.c
> @@ -42,8 +42,10 @@
>  /*********************************
>  * statistics
>  **********************************/
> -/* The number of compressed pages currently stored in zswap */
> +/* The number of pages currently stored in zswap */
>  atomic_long_t zswap_stored_pages = ATOMIC_LONG_INIT(0);
> +/* The number of incompressible pages currently stored in zswap */
> +atomic_long_t zswap_stored_incompressible_pages = ATOMIC_LONG_INIT(0);

Kernel test robot reported a sparse warning for the above line.  Andrew, could
you please add below attached fixup?


Thanks,
SJ

[...]

==== Attachment 0 (0001-mm-zswap-mark-zswap_stored_incompressible_pages-as-s.patch) ====
>From 1d41d75c47a6d3ef3cbf58636faf2b4dc04616ba Mon Sep 17 00:00:00 2001
From: SeongJae Park <sj@...nel.org>
Date: Thu, 21 Aug 2025 09:10:57 -0700
Subject: [PATCH] mm/zswap: mark zswap_stored_incompressible_pages as static

Only zswap.c uses zswap_stored_incompressible_pages, but it is not
marked as static.  This incurs a sparse warning that reported by kernel
teset robot.  Mark it as a static variable to eliminate the warning.

Reported-by: kernel test robot <lkp@...el.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202508211706.DnJPQQMn-lkp@intel.com/
Signed-off-by: SeongJae Park <sj@...nel.org>
---
 mm/zswap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/zswap.c b/mm/zswap.c
index 5dd282c5b626..ee443b317ac7 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -45,7 +45,7 @@
 /* The number of pages currently stored in zswap */
 atomic_long_t zswap_stored_pages = ATOMIC_LONG_INIT(0);
 /* The number of incompressible pages currently stored in zswap */
-atomic_long_t zswap_stored_incompressible_pages = ATOMIC_LONG_INIT(0);
+static atomic_long_t zswap_stored_incompressible_pages = ATOMIC_LONG_INIT(0);
 
 /*
  * The statistics below are not protected from concurrent access for
-- 
2.39.5