linux-kernel - Re: [PATCH V5 2/2] mm/khugepaged: retry with sync writeback for MADV

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Message-ID: <df4ca339-15aa-4346-bd66-00dc6002b630@kernel.org>
Date: Mon, 19 Jan 2026 11:08:05 +0100
From: "David Hildenbrand (Red Hat)" <david@...nel.org>
To: Shivank Garg <shivankg@....com>, Andrew Morton
 <akpm@...ux-foundation.org>, Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: Zi Yan <ziy@...dia.com>, Baolin Wang <baolin.wang@...ux.alibaba.com>,
 "Liam R . Howlett" <Liam.Howlett@...cle.com>, Nico Pache
 <npache@...hat.com>, Ryan Roberts <ryan.roberts@....com>,
 Dev Jain <dev.jain@....com>, Barry Song <baohua@...nel.org>,
 Lance Yang <lance.yang@...ux.dev>, Masami Hiramatsu <mhiramat@...nel.org>,
 Steven Rostedt <rostedt@...dmis.org>, linux-trace-kernel@...r.kernel.org,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Zach O'Keefe <zokeefe@...gle.com>, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, Stephen Rothwell <sfr@...b.auug.org.au>,
 Branden Moore <Branden.Moore@....com>
Subject: Re: [PATCH V5 2/2] mm/khugepaged: retry with sync writeback for
 MADV_COLLAPSE

On 1/18/26 20:09, Shivank Garg wrote:
> When MADV_COLLAPSE is called on file-backed mappings (e.g., executable
> text sections), the pages may still be dirty from recent writes.
> collapse_file() will trigger async writeback and fail with
> SCAN_PAGE_DIRTY_OR_WRITEBACK (-EAGAIN).
> 
> MADV_COLLAPSE is a synchronous operation where userspace expects
> immediate results. If the collapse fails due to dirty pages, perform
> synchronous writeback on the specific range and retry once.
> 
> This avoids spurious failures for freshly written executables while
> avoiding unnecessary synchronous I/O for mappings that are already clean.
> 
> Reported-by: Branden Moore <Branden.Moore@....com>
> Closes: https://lore.kernel.org/all/4e26fe5e-7374-467c-a333-9dd48f85d7cc@amd.com
> Fixes: 34488399fa08 ("mm/madvise: add file and shmem support to MADV_COLLAPSE")
> Suggested-by: David Hildenbrand <david@...nel.org>
> Tested-by: Lance Yang <lance.yang@...ux.dev>
> Signed-off-by: Shivank Garg <shivankg@....com>
> ---

Looks good to me now, thanks Shivank!

Acked-by: David Hildenbrand (Red Hat) <david@...nel.org>

-- 
Cheers

David