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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> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240607122357.115423-4-david@redhat.com> X-Spam-Level: X-Spamd-Result: default: False [-4.51 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; FUZZY_BLOCKED(0.00)[rspamd.com]; MISSING_XM_UA(0.00)[]; MIME_TRACE(0.00)[0:+]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; RCPT_COUNT_SEVEN(0.00)[8]; RCVD_TLS_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; DNSWL_BLOCKED(0.00)[2a07:de40:b281:104:10:150:64:97:from]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DKIM_TRACE(0.00)[suse.de:+] X-Rspamd-Action: no action X-Rspamd-Queue-Id: 38A28219BD X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Spam-Flag: NO X-Spam-Score: -4.51 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