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Mon, 10 Jun 2024 04:51:18 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id miCHK0aGZmbIHAAAD6G6ig (envelope-from ); Mon, 10 Jun 2024 04:51:18 +0000 Date: Mon, 10 Jun 2024 06:51:09 +0200 From: Oscar Salvador To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, Andrew Morton , Jonathan Corbet , "Kirill A . Shutemov" Subject: Re: [PATCH v1 3/6] fs/proc/task_mmu: properly detect PM_MMAP_EXCLUSIVE per page of PMD-mapped THPs Message-ID: References: <20240607122357.115423-1-david@redhat.com> <20240607122357.115423-4-david@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240607122357.115423-4-david@redhat.com> X-Rspamd-Action: no action X-Rspamd-Queue-Id: BD4C24000A X-Rspam-User: X-Rspamd-Server: rspam12 X-Stat-Signature: 3xqr6ufjeiw9r65dm8snfrx8ss9kdbof X-HE-Tag: 1717995080-900996 X-HE-Meta: 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 ZPyJpvO7 V2V0Yi59LY6cEyV4S8hW8lwgGB9Mo1681aHQzqFYmROBtA2rtTxD36CEVBcLSFaAO00cwcci7HKTBTt3H5/vRJ0CfhhSNTyqEIHbr5r4NzgCOtFQbU40SmOb19EQqCrpRQvNx1dso5C4FXi05G0n/4IuTY+H3iyvdz+aPMwNyk2n5r283nRLBqx4Q/908hQHLsfROACw93HpkeOPbZdev/QO80G3Q8qG7Hhx0F3DdkaIw/G9DhaAIboYtdidly7GgdwNZN1L0U/yerRw6h8HibkzbQy6L6cD4UUbMUen82JfzkEU= 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 Fri, Jun 07, 2024 at 02:23:54PM +0200, David Hildenbrand wrote: > We added PM_MMAP_EXCLUSIVE in 2015 via commit 77bb499bb60f ("pagemap: add > mmap-exclusive bit for marking pages mapped only here"), when THPs could > not be partially mapped and page_mapcount() returned something > that was true for all pages of the THP. > > In 2016, we added support for partially mapping THPs via > commit 53f9263baba6 ("mm: rework mapcount accounting to enable 4k mapping > of THPs") but missed to determine PM_MMAP_EXCLUSIVE as well per page. > > Checking page_mapcount() on the head page does not tell the whole story. > > We should check each individual page. In a future without per-page > mapcounts it will be different, but we'll change that to be consistent > with PTE-mapped THPs once we deal with that. > > Fixes: 53f9263baba6 ("mm: rework mapcount accounting to enable 4k mapping of THPs") > Cc: Kirill A. Shutemov > Signed-off-by: David Hildenbrand Reviewed-by: Oscar Salvador -- Oscar Salvador SUSE Labs