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Howlett" , David Hildenbrand , Vlastimil Babka , Jann Horn , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Mike Kaplinskiy , zhaozhengzhuo Subject: Re: [PATCH] mm/madvise: swap in CoW'd MAP_PRIVATE-file mappings on MADV_WILLNEED Message-Id: <20260905171757.ba8b0f8f0f18ebd04418bfeb@linux-foundation.org> In-Reply-To: References: <20260904-madv-will-need-map-private-v1-1-6b83cc99fcff@kernel.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 66BA614000D X-Stat-Signature: ck5e7og41q94bq76ks57cbsciogoa6yk X-Rspam-User: X-HE-Tag: 1788653879-543120 X-HE-Meta: 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 oDY4Xhpc 3cdCyBhnzN72TeDJkdwn0ApuO5zqu60xsSeBm5AUkI53emV68MVEnSF2lyme3//yp9O1o7O4+UhD5O3Gn9ZkF+Cpj+Zuw8i3jFTek5wcLRI5g9wSSRHlp0nueQVYhekbXbLRSMEZn688ztzH7xrQYLz2w8vyYTVwZjLh49vjhWtsTN+jYcEHz0kpnQbvdDlmY74kHQ4V6xAMJoJu1PB11N2eMGEWpbi/UMhYu5esHDE/nmkreWktk0qx1WKGwtPk7xtVhAQTrdJ7waKwRkg2YtPizmsBd51aeL7zGtFeQ9IVb3Io+NLYKWCbpgIPD3uSC2pst94zZp+LB7K9epaBFDNkUWw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, 4 Sep 2026 17:01:37 +0100 "Lorenzo Stoakes (ARM)" wrote: > Andrew - could you swap the patch out in-place with below? Thanks! > np. > Currently MADV_WILLNEED treats file-backed and pure anonymous mappings > entirely separately - using POSIX_FADV_WILLNEED (equivalent of a readahead) > for the former and a tree walk and swap in to swap cache for the latter. > > MAP_PRIVATE-file backed mappings straddle the two and currently get treated > as if they were purely file-backed, meaning any swapped out private pages > remain swapped out. > > Resolve the issue by explicitly checking for CoW'd MAP_PRIVATE-file backed > mappings and performing both walks in this case. > > Since the logic checks for vma->anon_vma this means un-CoW'd > MAP_PRIVATE-file backed mappings retain only the single file walk. > > Reported-by: Mike Kaplinskiy > Closes: https://lore.kernel.org/all/CABeknB_S2XJSHFgnHdgnN0rjzHhH4oQJs_APq9fvxHztQ_pgiA@mail.gmail.com/ > Signed-off-by: Lorenzo Stoakes (ARM) The failure mode looks pretty obscure, so I'm thinking that no backport is needed.