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Tue, 20 Jan 2026 06:19:49 -0500 (EST) Date: Tue, 20 Jan 2026 11:19:47 +0000 From: Kiryl Shutsemau To: "David Hildenbrand (Red Hat)" Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Qi Zheng Subject: Re: [PATCH v1 1/2] mm: move pte table reclaim code to memory.c Message-ID: References: <20260119220708.3438514-1-david@kernel.org> <20260119220708.3438514-2-david@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260119220708.3438514-2-david@kernel.org> X-Rspam-User: X-Stat-Signature: hsq95apupu6kyfixmzdo5mcso3xezf61 X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: F1377180005 X-HE-Tag: 1768907991-66994 X-HE-Meta: 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 RCvcktPX sEXKvOk5AF1EyKHAHQeJnVY6ThL3eZIG3f0WkH2N6rAcfCSxm+SY96xseMJRoiTM50kOVJNaODcs7C5yJwmjzhyC4cXVHkB58EgspbHT84QowYXG6Qsav615+vKR8DU+MgrahP812gKvutIaFTNJVuvMI9mEt3U/xH4k0otXYdl6ZeNi/q9WxRvvZyngcKF7ovlg9FWEFtnS7TGppRYOEPjHILHRsaKgBM80YzMGRsiz8JQwVOBdNYuySi6tuh5CKqeNxDBFqLCmXDpvag7twkESzLwwMdOU0hBUL/9srZt8VB/llLknWzwAHGYGMangacP6C9vkwYiI7b4uheo1iOhCc5phHRJrVe1GO9zPnbN77LJ+VUeBg3P63Ip2+0KCgZfZl+GyY3YaxOcWHiBqNcP0dc7Qrp20XKOSrPvj6gDk0GHpYiS1vKpzssQ== 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, Jan 19, 2026 at 11:07:07PM +0100, David Hildenbrand (Red Hat) wrote: > The pte-table reclaim code is only called from memory.c, while zapping > pages, and it better also stays that way in the long run. If we ever > have to call it from other files, we should expose proper high-level > helpers for zapping if the existing helpers are not good enough. > > So, let's move the code over (it's not a lot) and slightly clean it up a > bit by: > - Renaming the functions. > - Dropping the "Check if it is empty PTE page" comment, which is now > self-explaining given the function name. > - Making zap_pte_table_if_empty() return whether zapping worked so the > caller can free it. > - Adding a comment in pte_table_reclaim_possible(). > - Inlining free_pte() in the last remaining user. > - In zap_empty_pte_table(), switch from pmdp_get_lcokless() to > pmd_clear(), we are holding the PMD PT lock. > > By moving the code over, compilers can also easily figure out when > zap_empty_pte_table() does not initialize the pmdval variable, avoiding > false-positive warnings about the variable possibly not being > initialized. mm/memory.c is a kitchen sink as it is. I think you miss opportunity to introduce mm/zap.c and move all zap code. It can be done for code from both mm/memory.c and mm/huge_memory.c. Line between THP and non-THP code gets more and more blurry over time. The same can be done for copy and fault code. I think it is going to be more maintainable this way. -- Kiryl Shutsemau / Kirill A. Shutemov