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Wed, 03 Dec 2025 17:55:06 -0800 (PST) Received: from localhost.localdomain ([2409:8900:1be3:8f38:b904:5201:d897:3883]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-34930b5a195sm915502a91.3.2025.12.03.17.54.55 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); 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> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: E2475160015 X-Stat-Signature: d8uugwythawdinj3x54x5tena8jxq1ci X-Rspam-User: X-HE-Tag: 1764813307-25532 X-HE-Meta: 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 sWK3N/vs 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: > 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