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Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: References: <614257.1719228181@warthog.procyon.org.uk> To: Matthew Wilcox Cc: dhowells@redhat.com, Christian Brauner , Jeff Layton , netfs@lists.linux.dev, v9fs@lists.linux.dev, linux-afs@lists.infradead.org, linux-cifs@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] netfs: Fix netfs_page_mkwrite() to check folio->mapping is valid MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <720578.1719268838.1@warthog.procyon.org.uk> Date: Mon, 24 Jun 2024 23:40:38 +0100 Message-ID: <720579.1719268838@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 X-Stat-Signature: etwobntc19io6amw7f15xqz89bc6s8gg X-Rspamd-Queue-Id: 94E0CC000E X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1719268849-836950 X-HE-Meta: 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 5VDeCIw7 UqnS9dampu6/NKMiaZ0PZVyD3XUM16dqzbkPJzEbqjoQu8TsvfS6IsugpE1+X5KJP/5datfsjgzzqXVsuopnXFpMOuMWK9lpJMpkF/lKuus2JQyeTyTUOk4T2xdZncyiK2QZkWle7qjyTopgJOzBhCfj91yKFPJTcuG9we/1BO90DLtjD4GJuhyHZuDTj1Icbg8arxu7AIbwk/PItvdK2eSXTHkeA30AzU5HC7Pr7Z+KFD7K+TPfyRSuSoDqPCBlIX5cN4x67OKrwGXAGo28rDFQe+DKIbiQ8SN3yNS31EJIF4HCwT4WXhtbzlBD2NNgFDVJ/mJMEwR56B0FSoweTLuUFFAlZBP6hX/vsOmzoj73S+08oDdrkr1zl/gDvm2bnyFiu 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: Matthew Wilcox wrote: > > if (folio_lock_killable(folio) < 0) > > goto out; > > + if (folio->mapping != mapping) { > > + ret = VM_FAULT_NOPAGE | VM_FAULT_LOCKED; > > + goto out; > > + } > > Have you tested this? I've tried to. generic/247 can trigger it, but the race happens rarely. > I'd expect it to throw some VM assertions. I didn't see any. I guess VM_FAULT_LOCKED is not universally handled by the caller and that I should unlock the folio myself instead. David