Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.33 as permitted sender) client-ip=23.128.96.33;
Date:   Mon, 6 Nov 2023 14:28:27 -0500
From:   Johannes Weiner <hannes@cmpxchg.org>
To:     Stefan Roesch <shr@devkernel.io>
Cc:     kernel-team@fb.com, akpm@linux-foundation.org, riel@surriel.com,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH v1] mm: Fix for negative counter: nr_file_hugepages
Message-ID: <20231106192827.GA3661273@cmpxchg.org>
References: <20231106181918.1091043-1-shr@devkernel.io>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20231106181918.1091043-1-shr@devkernel.io>
Precedence: bulk

On Mon, Nov 06, 2023 at 10:19:18AM -0800, Stefan Roesch wrote:
> While qualifiying the 6.4 release, the following warning was detected in
> messages:
> 
> vmstat_refresh: nr_file_hugepages -15664
> 
> The warning is caused by the incorrect updating of the NR_FILE_THPS
> counter in the function split_huge_page_to_list. The if case is checking
> for folio_test_swapbacked, but the else case is missing the check for
> folio_test_pmd_mappable. The other functions that manipulate the counter
> like __filemap_add_folio and filemap_unaccount_folio have the
> corresponding check.
> 
> I have a test case, which reproduces the problem. It can be found here:
>   https://github.com/sroeschus/testcase/blob/main/vmstat_refresh/madv.c
> 
> The test case reproduces on an XFS filesystem. Running the same test
> case on a BTRFS filesystem does not reproduce the problem.
> 
> AFAIK version 6.1 until 6.6 are affected by this problem.
> 
> Signed-off-by: Stefan Roesch <shr@devkernel.io>
> Co-debugged-by: Johannes Weiner <hannes@cmpxchg.org>

With the newline fix Willy pointed out, and CC: stable:

Acked-by: Johannes Weiner <hannes@cmpxchg.org>