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Fri, 20 Jun 2025 12:30:29 +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 EGLmGmVUVWjNKAAAD6G6ig (envelope-from ); Fri, 20 Jun 2025 12:30:29 +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 v2 4/5] mm,hugetlb: Drop obsolete comment about non-present pte and second faults Date: Fri, 20 Jun 2025 14:30:13 +0200 Message-ID: <20250620123014.29748-5-osalvador@suse.de> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250620123014.29748-1-osalvador@suse.de> References: <20250620123014.29748-1-osalvador@suse.de> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Queue-Id: 3046AC0014 X-Rspamd-Server: rspam10 X-Stat-Signature: 5exadnx5roakeeh4tqo8nezrfny9m1a4 X-HE-Tag: 1750422635-671397 X-HE-Meta: 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 iZEQE8OG 8J59SgdVO3tCOrXvky8ZHPBlYljShGEswI4OCXFBxFI82wS/3mEwtP7cIIJuCoUwQP8mwi3hzTuRE/CgdKHfVQrPNnQYZvO+2DkQbyVZUUXshP2OXenPG8cZybvmuLBcXPqvLw9ig5Hs9vgRhleLmRyF1c2utfLaK3NII+4rt4x9XLxNTQT1E84l469Ce9L+tpPJCBtBFU5SDsqmrMQ66hyLWbpZEg9Q8Eehnl7BNFbBwkLH2GE5HXWWbJmNUdN8FyfAr 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 57bb8b2dce21..868ee8ed45c0 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -6746,13 +6746,7 @@ 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