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Received: from willy by casper.infradead.org with local (Exim 4.97.1 #2 (Red Hat Linux)) id 1rmCpA-0000000HDQ3-1MEa; Mon, 18 Mar 2024 13:14:44 +0000 Date: Mon, 18 Mar 2024 13:14:44 +0000 From: Matthew Wilcox To: alexs@kernel.org Cc: kasong@tencent.com, Andrew Morton , "open list:MEMORY MANAGEMENT" , open list Subject: Re: [PATCH 01/12] mm/ksm: catch tail page abnormal in page_stable_node Message-ID: References: <20240318121443.3991104-1-alexs@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240318121443.3991104-1-alexs@kernel.org> X-Rspam-User: X-Stat-Signature: abyum7bprc83uwo44k1wosi3yad3yuoq X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 3057CC0034 X-HE-Tag: 1710767691-223510 X-HE-Meta: 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 ZYjKgzmY TEEKjjC2/FwbNJMo6X54TUHDZtbsgIKoCddAOZUmSsfN04dpxlQcQki2/PCCwlgeKLdxArdYnPJRK+lCPGKijqdLpqEDPbMF2i9oyqa7ElV5ZSUMHBUc+Vb0iN8QQBh87+7QXak85K2lpbPxHzdPpw/g3Xsps6+HzD2jbfaFhhmLzov/xWvw0GVH7y+PFiEXwjGc4L5BQ8tnkIc3JKQw2cwqVXuX16AMfM9jdB7b7i+jGXPg= 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: On Mon, Mar 18, 2024 at 08:14:30PM +0800, alexs@kernel.org wrote: > From: Alex Shi > > commit 19138349ed59 ("mm/migrate: Add folio_migrate_flags()") change the > meaning of func page_stable_node() to check the compound head for tail > 'page' instead of tail page self. > But seems both semantics are same at results, the func always return NULL > for tail page. So adding a bug monitor here in case of abnormal. No. I didn't object to you doing this to convince yourself, but there's no way we should have this upstream. If we did have large KSM folios (and I don't think we should!), you'd crash the kernel instead of silently doing the right thing. > static inline struct ksm_stable_node *page_stable_node(struct page *page) > { > - return folio_stable_node(page_folio(page)); > + struct ksm_stable_node *node; > + > + node = folio_stable_node(page_folio(page)); > + VM_BUG_ON_PAGE(PageTail(page) && node, page); > + > + return node; > }