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b=hZV6kriX7nqpeD/vjJn13zCehc wy+WRvLpFUrnbR1i/8VFcEoU5fZ7P6IcO9HAiDwPU9Y3O7Vi37TYKqkOsKC8m3optDaKOtQbNv6IT ss2cjl+f1umh9Hz7JB32YovekERtB+qlR5Zoc9KHxly8LajlE/poezIBAxnUIUhKgljsaondbbotN oJ3CzqukXTdvGU21l7pvC47RYEO4i6ijn+5ATuopSr3czOxQ41MUDtEvUuozy/Q+v25aoljs6CSxD JfUM9ogMtmPDJSN2F7tvwgbZ7cYDp46i4HVwS7JWjigCWQETbOicNdi+7OwXZhAfCMI2FLfuHT4Sk chYdPHTQ==; Received: from willy by casper.infradead.org with local (Exim 4.99.1 #2 (Red Hat Linux)) id 1x8fPc-00000004Tjk-3iUT; Mon, 21 Sep 2026 14:54:32 +0000 Date: Mon, 21 Sep 2026 15:54:32 +0100 From: Matthew Wilcox To: Johannes Weiner Cc: "Vlastimil Babka (SUSE)" , Matt Fleming , Salvatore Dipietro , akpm@linux-foundation.org, abuehaze@amazon.com, alisaidi@amazon.com, blakgeof@amazon.com, brauner@kernel.org, brendan.jackman@linux.dev, david@redhat.com, dgc@kernel.org, dipietro.salvatore@gmail.com, djwong@kernel.org, hch@infradead.org, hch@lst.de, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-xfs@vger.kernel.org, mhocko@suse.com, ritesh.list@gmail.com, rvvandan@amazon.com, stable@vger.kernel.org, surenb@google.com, ziy@nvidia.com Subject: Re: [PATCH 1/2] mm: page_alloc: do not give all non-blocking requests reserve access Message-ID: References: <20260905174239.99e31515fabe220aa7d8e6fa@linux-foundation.org> <20260910114602.926944-1-dipiets@amazon.it> <8d6a8a63-4adc-458a-b548-a47bf5ff8eb7@kernel.org> <9f415dc7-adad-4161-b20d-7c3173f50ff3@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: B996C10000F X-Stat-Signature: gm8n7n678t5i3uwqhu4uef7qhogisyzn X-HE-Tag: 1790002479-882267 X-HE-Meta: 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 Jd8gwGPz DHGqMbFuKFtjpu3axzZ9BNKzIK6Mj8+mFk8eVl81ZRiF1BWKX8BZwOoDYuVjnb0ApZ81/1RH44SpDOJtIyOEYA8y/fISpMISFkynlFTPrQ6GR2rSQckDDZfHEI8ARKDcU6Fb3Yk5P8qXVuuXG23JAWQMVZM1gCKwCmBY3LnM/RaOgAEa7FU/kxPxu9Znk0FHnevXOeYXrtqHfj+oqls8Kjn/CW9NQ3tffRlb01/aIlSx4GN5IYsCQp0wUid4Pl+bkyS8ApOPqXykktWU9cAML1LkpmKtH6WrIxLYKTqzxVulkarhJgl+OebxzbCKJn7jYacyfYRaE5mGf3eozK+T1A2tyNB34dUbgT9eXAJPVeT2+/7U0DlKALsJiQs3pJVSF2h5ACYurkdXNr58= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Sep 21, 2026 at 10:38:18AM -0400, Johannes Weiner wrote: > +++ b/mm/page_alloc.c > @@ -3246,7 +3246,9 @@ struct page *rmqueue_buddy(struct zone *preferred_zone, struct zone *zone, > * reserves as failing now is worse than failing a > * high-order atomic allocation in the future. > */ > - if (!page && (alloc_flags & (ALLOC_OOM|ALLOC_NON_BLOCK))) > + if (!page && > + ((alloc_flags & ALLOC_OOM) || > + (alloc_flags & ALLOC_MASK_ATOMIC) == ALLOC_MASK_ATOMIC)) > page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC); Would this be slightly neater? static inline bool may_access_reserves(unsigned int alloc_flags) { if (alloc_flags & ALLOC_OOM) return true; if (alloc_flags & (ALLOC_NON_BLOCK | ALLOC_MIN_RESERVE)) == (ALLOC_NON_BLOCK | ALLOC_MIN_RESERVE) return true; return false; } [...] - if (!page && (alloc_flags & (ALLOC_OOM|ALLOC_NON_BLOCK))) + if (!page && may_access_reserves(alloc_flags)) page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC);