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Wed, 11 Nov 2026 17:51:28 +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:T6 (envelope-from ); Wed, 11 Nov 2026 17:51:28 +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 5/8] mm/khugepaged: simplify prepare folio locking and exit paths Date: Wed, 11 Nov 2026 17:51:18 +0000 Message-ID: <20261111175121.1328383-6-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 folio_trylock() + folio_get() do the exact same thing on both is_shmem and !is_shmem paths. Unify them into one path. At the end of the day, there are two large invariants for the function: - xarray lock is not held at exit. Either it was dropped on error, or dropped on success/IO. - success always means a locked-and-ref'd-up folio. After this transformation, it's trivial to notice how simple the error paths are, so do away with the gotos and hoist some code. Signed-off-by: Pedro Falcato --- mm/khugepaged.c | 33 +++++++++++---------------------- 1 file changed, 11 insertions(+), 22 deletions(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 0eee2b6bbe64..236df9be7e27 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -2314,7 +2314,8 @@ prepare_collapse_file_folio(pgoff_t index, struct collapse_file_state *state) * will not succeed. */ lru_add_drain(); - goto xa_unlocked; + state->folio = folio; + return SCAN_SUCCEED; } if (!is_shmem) { @@ -2337,31 +2338,19 @@ prepare_collapse_file_folio(pgoff_t index, struct collapse_file_state *state) xas_unlock_irq(state->xas); if (dirty && !inode_is_open_for_write(mapping->host)) filemap_flush(mapping); - result = SCAN_PAGE_DIRTY_OR_WRITEBACK; - goto xa_unlocked; - } - } - - if (is_shmem) { - if (folio_trylock(folio)) { - folio_get(folio); - } else { - result = SCAN_PAGE_LOCK; - goto xa_locked; - } - } else { /* !is_shmem */ - if (folio_trylock(folio)) { - folio_get(folio); - } else { - result = SCAN_PAGE_LOCK; - goto xa_locked; + return SCAN_PAGE_DIRTY_OR_WRITEBACK; } } -xa_locked: + /* + * Note: trylock + simple folio_get() is safe here due to the i_pages + * lock being held; this excludes truncation happening in parallel. + */ + if (!folio_trylock(folio)) + result = SCAN_PAGE_LOCK; + else + folio_get(folio); xas_unlock_irq(state->xas); -xa_unlocked: - state->folio = folio; return result; } -- 2.56.0