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Wed, 10 Sep 2025 15:19:08 -0700 (PDT) Date: Wed, 10 Sep 2025 15:19:08 -0700 (PDT) From: "Christoph Lameter (Ampere)" To: "Matthew Wilcox (Oracle)" cc: Vlastimil Babka , Andrew Morton , David Rientjes , Roman Gushchin , Harry Yoo , linux-mm@kvack.org Subject: Re: [PATCH v2 01/22] slab: Remove unnecessary test from alloc_debug_processing() In-Reply-To: <20250910115507.1991829-2-willy@infradead.org> Message-ID: <364922eb-4ada-ff27-1338-26197aee5e33@gentwo.org> References: <20250910115507.1991829-1-willy@infradead.org> <20250910115507.1991829-2-willy@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: D100D40003 X-Stat-Signature: 6qzg7r7p17sihsrgyzezwq1cjy5e5btu X-HE-Tag: 1757542749-492178 X-HE-Meta: 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 8Znpixwh I7BgidbQ/QYzWLC8v1aYFByZVGZF517d4vLQp6v2WlpQBczjfq27nScIuSi13x00PqlSEXjQ2o0E9XXJNMAPCyO0QVQbM3yeolN6PNjo1oRUUtrZZteyNK3XLgVwPfKGsdcSLPhVXwgs0QCUfUrxRciwaGIcKv+d0v/XTRhDQb74IexoJd1BCZEc+BsLCJMUFanE/cy7qZu6E6wCUNOyRBigocppFMjjHBoBmgjTT+6FTtSkW83DWKz06P7Az2WkC/2LXLsRaDLdaPBl2R2opKA5lLggBYH/6no6dzcJR1aDUrbMg6oEoZoOoNVR3u0U/c9HjXQS6IsWLGcI= 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 Wed, 10 Sep 2025, Matthew Wilcox (Oracle) wrote: > In alloc_debug_processing() we know that the slab pointer passed in > really is a pointer to a slab. Both callers modify members of the slab > data structure. So we can remove this check. The code modified here is the case where consistency checks on a slab page have failed. The pointer to the slab page could be a random pointer. Thus we should not assume that this is a slab page and modify values of some other structure that may have some other relevance.