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Fri, 27 Jun 2025 10:29:17 +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 6HFqDn1yXmgIAgAAD6G6ig (envelope-from ); Fri, 27 Jun 2025 10:29:17 +0000 From: Oscar Salvador To: Andrew Morton Cc: David Hildenbrand , Muchun Song , Peter Xu , Gavin Guo , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Oscar Salvador Subject: [PATCH v3 4/5] mm,hugetlb: Drop obsolete comment about non-present pte and second faults Date: Fri, 27 Jun 2025 12:29:03 +0200 Message-ID: <20250627102904.107202-5-osalvador@suse.de> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250627102904.107202-1-osalvador@suse.de> References: <20250627102904.107202-1-osalvador@suse.de> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Action: no action X-Rspamd-Queue-Id: 47392140008 X-Stat-Signature: ce1jnkqixjrqhmerqg79buujap7u7mac X-Rspamd-Server: rspam09 X-Rspam-User: X-HE-Tag: 1751020162-666016 X-HE-Meta: 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 /C+uLryG HmIxrrxeMpZzGX+6mN7uUpzGw5pMI06c0DTBiWGuNKnz5GPYdUpH7TDQPQR10qLTuElhvhL2sfVd7Q9vhhBhCl6/a7OYZVLoSm/bjjxs41AeEVsSYwEViX2AonjM2Ack75UCvuGSqoh1T12XuZtcrz7HBeZkXcKNbX6PbyBK2g0pgWg18YBS3o61KDiyNm0IyJwdHbfwSFi9O6RE03gSR+hxx9AL9quGMtoJcbEXPhU5yaUSdEnMI3APXqfPb5oViIJCGfmw0ZFfB2vVE8XZ9atNn/cbxaoNvA1m9 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: There is a comment in hugetlb_fault() that does not hold anymore. This one: /* * vmf.orig_pte could be a migration/hwpoison vmf.orig_pte at this * point, so this check prevents the kernel from going below assuming * that we have an active hugepage in pagecache. This goto expects * the 2nd page fault, and is_hugetlb_entry_(migration|hwpoisoned) * check will properly handle it. */ This was written because back in the day we used to do: hugetlb_fault () { ptep = huge_pte_offset(...) if (ptep) { entry = huge_ptep_get(ptep) if (unlikely(is_hugetlb_entry_migration(entry)) ... else if (unlikely(is_hugetlb_entry_hwpoisoned(entry))) ... } ... ... /* * entry could be a migration/hwpoison entry at this point, so this * check prevents the kernel from going below assuming that we have * a active hugepage in pagecache. This goto expects the 2nd page fault, * and is_hugetlb_entry_(migration|hwpoisoned) check will properly * handle it. */ if (!pte_present(entry)) goto out_mutex; ... } The code was designed to check for hwpoisoned/migration entries upfront, and then bail out if further down the pte was not present anymore, relying on the second fault to properly handle migration/hwpoison entries that time around. The way we handle this is different nowadays, so drop the misleading comment. Signed-off-by: Oscar Salvador --- mm/hugetlb.c | 8 +------- 1 file changed, 1 insertion(+), 7 deletions(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index b110394d8d6e..0a6a519fabe5 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -6747,13 +6747,7 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma, ret = 0; - /* - * vmf.orig_pte could be a migration/hwpoison vmf.orig_pte at this - * point, so this check prevents the kernel from going below assuming - * that we have an active hugepage in pagecache. This goto expects - * the 2nd page fault, and is_hugetlb_entry_(migration|hwpoisoned) - * check will properly handle it. - */ + /* Not present, either a migration or a hwpoisoned entry */ if (!pte_present(vmf.orig_pte)) { if (unlikely(is_hugetlb_entry_migration(vmf.orig_pte))) { /* -- 2.50.0