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	Mon, 10 Nov 2025 14:17:36 +0000
Date: Mon, 10 Nov 2025 14:17:36 +0000
From: Matthew Wilcox <willy@infradead.org>
To: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Shivank Garg <shivankg@amd.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	David Hildenbrand <david@redhat.com>, Zi Yan <ziy@nvidia.com>,
	Baolin Wang <baolin.wang@linux.alibaba.com>,
	"Liam R . Howlett" <Liam.Howlett@oracle.com>,
	Nico Pache <npache@redhat.com>, Ryan Roberts <ryan.roberts@arm.com>,
	Dev Jain <dev.jain@arm.com>, Barry Song <baohua@kernel.org>,
	Lance Yang <lance.yang@linux.dev>,
	Steven Rostedt <rostedt@goodmis.org>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Zach O'Keefe <zokeefe@google.com>, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
	Branden Moore <Branden.Moore@amd.com>
Subject: Re: [PATCH 1/2] mm/khugepaged: do synchronous writeback for
 MADV_COLLAPSE
Message-ID: <aRH0ANHpP8VN1j9r@casper.infradead.org>
References: <20251110113254.77822-1-shivankg@amd.com>
 <aRHs3pA2kOr_uD3k@casper.infradead.org>
 <b7313a45-c36e-4390-a0b8-46f412474f86@lucifer.local>
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In-Reply-To: <b7313a45-c36e-4390-a0b8-46f412474f86@lucifer.local>

On Mon, Nov 10, 2025 at 01:52:46PM +0000, Lorenzo Stoakes wrote:
> On Mon, Nov 10, 2025 at 01:47:10PM +0000, Matthew Wilcox wrote:
> > On Mon, Nov 10, 2025 at 11:32:53AM +0000, 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. The
> >
> > That explanation derails my brain entirely.  Text isn't writable!  How
> > can the pages be dirty and file-backed text?
> 
> Because they just compiled it and it's not been written back to disk yet :)

So we can avoid these patches simply by changing userspace to call
fsync()?  Cool!