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Wed, 03 Dec 2025 17:55:06 -0800 (PST) From: wang lian To: shivankg@amd.com Cc: Branden.Moore@amd.com, Liam.Howlett@oracle.com, akpm@linux-foundation.org, baohua@kernel.org, baolin.wang@linux.alibaba.com, david@kernel.org, dev.jain@arm.com, lance.yang@linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, lorenzo.stoakes@oracle.com, mathieu.desnoyers@efficios.com, mhiramat@kernel.org, npache@redhat.com, rostedt@goodmis.org, ryan.roberts@arm.com, ziy@nvidia.com, zokeefe@google.com, wang lian Subject: Re: [PATCH V3 1/2] mm/khugepaged: map dirty/writeback pages failures to EAGAIN Date: Thu, 4 Dec 2025 09:54:25 +0800 Message-ID: <20251204015425.66988-1-lianux.mm@gmail.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20251201185604.210634-8-shivankg@amd.com> References: <20251201185604.210634-8-shivankg@amd.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit > When collapse_file encounters dirty or writeback pages in file-backed > mappings, it currently returns SCAN_FAIL which maps to -EINVAL. This is > misleading as EINVAL suggests invalid arguments, whereas dirty/writeback > pages represent transient conditions that may resolve on retry. > > Introduce SCAN_PAGE_DIRTY_OR_WRITEBACK to cover both dirty and writeback > states, mapping it to -EAGAIN. For MADV_COLLAPSE, this provides userspace > with a clear signal that retry may succeed after writeback completes. > For khugepaged, this is harmless as it will naturally revisit the range > during periodic scans after async writeback completes. > > Reported-by: Branden Moore > 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") > Reviewed-by: Dev Jain > Reviewed-by: Lance Yang > Signed-off-by: Shivank Garg > --- LGTM. Reviewed-by: wang lian -- Best Regards, wang lian