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Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1qYbkx-001lhU-49; Wed, 23 Aug 2023 00:29:55 +0000 Date: Wed, 23 Aug 2023 01:29:55 +0100 From: Matthew Wilcox To: Mike Kravetz Cc: Andrew Morton , Jens Axboe , io-uring@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v2 10/13] mm: Free up a word in the first tail page Message-ID: References: <20230816151201.3655946-1-willy@infradead.org> <20230816151201.3655946-11-willy@infradead.org> <20230822231741.GC4509@monkey> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230822231741.GC4509@monkey> X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 19554A0013 X-Stat-Signature: 3tpbc48pf4zm66zgn5ayrmaa958hk7mx X-Rspam-User: X-HE-Tag: 1692750603-175337 X-HE-Meta: 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 /FyZhHEG JU3x15mW0dkOI0O2LJIyuH6rdCsgHp9bLBSZfvjJbhKWJh30dCQ9+NwbfGUzAY1Td6QzYN2oDFnetdSxNHPsB3nWbWgVHvUvF0lUkoB/aH+ZLBqaRDwvRENPQ+NzbFW7Y0H53D361B6Ikt2H0IClG397De6r1i/vVnfTs 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: On Tue, Aug 22, 2023 at 04:17:41PM -0700, Mike Kravetz wrote: > On 08/16/23 16:11, Matthew Wilcox (Oracle) wrote: > > Store the folio order in the low byte of the flags word in the first > > tail page. This frees up the word that was being used to store the > > order and dtor bytes previously. > > hugetlb manually creates and destroys compound pages. As such it makes > assumptions about struct page layout. This breaks hugetlb. The following > will allow fix the breakage. > > The hugetlb code is quite fragile when changes like this are made. I am > open to suggestions on how we can make this more robust. Perhaps start > with a simple set of APIs to create_folio from a set of contiguous pages > and destroy a folio? Thanks; those changes look good to me. I don't have any _immediate_ plans to make your life easier. When we get to a memdesc world, it'll all get much easier.