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Wed, 11 Nov 2026 17:51:31 +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 +SJmCxur9GphXQAAD6G6ig:T9 (envelope-from ); Wed, 11 Nov 2026 17:51:31 +0000 From: Pedro Falcato To: Andrew Morton , David Hildenbrand , Zi Yan Cc: Pedro Falcato , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Lorenzo Stoakes , Kiryl Shutsemau , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 8/8] mm/khugepaged: flesh out try_to_unmap_flush() comment Date: Wed, 11 Nov 2026 17:51:21 +0000 Message-ID: <20261111175121.1328383-9-pfalcato@suse.de> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261111175121.1328383-1-pfalcato@suse.de> References: <20261111175121.1328383-1-pfalcato@suse.de> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Spamd-Result: default: False [-15.80 / 50.00]; SUSE_INTERNAL_BYPASS(-9.00)[]; REPLY(-4.00)[]; BAYES_HAM(-3.00)[100.00%]; MID_CONTAINS_FROM(1.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_MISSING_CHARSET(0.50)[]; NEURAL_HAM_SHORT(-0.20)[-0.995]; MIME_GOOD(-0.10)[text/plain]; MIME_TRACE(0.00)[0:+]; ARC_NA(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; TO_DN_SOME(0.00)[]; RCPT_COUNT_TWELVE(0.00)[16]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:email]; RCVD_VIA_SMTP_AUTH(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; FROM_HAS_DN(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; R_RATELIMIT(0.00)[to_ip_from(RL8d8xedm6iu8o66torxsk6bwd)]; RCVD_TLS_ALL(0.00)[] X-Spam-Score: -15.80 X-Spam-Level: X-Spam-Flag: NO Flesh out any correctness concerns with try_to_unmap batching, flushing and its interaction with the rest of collapse_file(). Signed-off-by: Pedro Falcato --- mm/khugepaged.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index accd8b4895d3..fd947e698ed0 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -2597,8 +2597,12 @@ static enum scan_result collapse_file(struct mm_struct *mm, unsigned long addr, xa_unlocked: /* - * Flush before copying the folios, or releasing them in rollback. - * This is a no-op if out_unlock already flushed the batch. + * try_to_unmap() flush must be done now before copying, regardless + * of success or not. In case of success, folios are about to be + * copied and collapsed onto a single large folio. In that case, + * stale TLB entries need to be flushed out, so no racing write may + * get lost. In case of failure, stale TLB entries need to be flushed + * out before putting the folio (which can possibly free it). */ try_to_unmap_flush(); -- 2.56.0