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[153.127.16.23]) by smtp.gmail.com with ESMTPSA id r10-20020a170903020a00b00168eab11f67sm362571plh.94.2022.06.23.16.52.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 23 Jun 2022 16:52:36 -0700 (PDT) From: Naoya Horiguchi X-Google-Original-From: Naoya Horiguchi To: linux-mm@kvack.org Cc: Andrew Morton , David Hildenbrand , Mike Kravetz , Miaohe Lin , Liu Shixin , Yang Shi , Oscar Salvador , Muchun Song , Naoya Horiguchi , linux-kernel@vger.kernel.org Subject: [PATCH v2 3/9] mm/hugetlb: make pud_huge() and huge_pud() aware of non-present pud entry Date: Fri, 24 Jun 2022 08:51:47 +0900 Message-Id: <20220623235153.2623702-4-naoya.horiguchi@linux.dev> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220623235153.2623702-1-naoya.horiguchi@linux.dev> References: <20220623235153.2623702-1-naoya.horiguchi@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Naoya Horiguchi follow_pud_mask() does not support non-present pud entry now. As long as I tested on x86_64 server, follow_pud_mask() still simply returns no_page_table() for non-present_pud_entry() due to pud_bad(), so no severe user-visible effect should happen. But generally we should call follow_huge_pud() for non-present pud entry for 1GB hugetlb page. Update pud_huge() and huge_pud() to handle non-present pud entries. The changes are similar to previous works for pud entries commit e66f17ff7177 ("mm/hugetlb: take page table lock in follow_huge_pmd()") and commit cbef8478bee5 ("mm/hugetlb: pmd_huge() returns true for non-present hugepage"). Signed-off-by: Naoya Horiguchi --- arch/x86/mm/hugetlbpage.c | 3 ++- mm/hugetlb.c | 26 +++++++++++++++++++++++++- 2 files changed, 27 insertions(+), 2 deletions(-) diff --git a/arch/x86/mm/hugetlbpage.c b/arch/x86/mm/hugetlbpage.c index a0d023cb4292..5fb86fb49ba8 100644 --- a/arch/x86/mm/hugetlbpage.c +++ b/arch/x86/mm/hugetlbpage.c @@ -70,7 +70,8 @@ int pmd_huge(pmd_t pmd) int pud_huge(pud_t pud) { - return !!(pud_val(pud) & _PAGE_PSE); + return !pud_none(pud) && + (pud_val(pud) & (_PAGE_PRESENT|_PAGE_PSE)) != _PAGE_PRESENT; } #endif diff --git a/mm/hugetlb.c b/mm/hugetlb.c index f59f43c06601..b7ae5f73f3b2 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -6946,10 +6946,34 @@ struct page * __weak follow_huge_pud(struct mm_struct *mm, unsigned long address, pud_t *pud, int flags) { + struct page *page = NULL; + spinlock_t *ptl; + pte_t pte; + if (flags & (FOLL_GET | FOLL_PIN)) return NULL; - return pte_page(*(pte_t *)pud) + ((address & ~PUD_MASK) >> PAGE_SHIFT); +retry: + ptl = huge_pte_lock(hstate_sizelog(PUD_SHIFT), mm, (pte_t *)pud); + if (!pud_huge(*pud)) + goto out; + pte = huge_ptep_get((pte_t *)pud); + if (pte_present(pte)) { + page = pud_page(*pud) + ((address & ~PUD_MASK) >> PAGE_SHIFT); + if (WARN_ON_ONCE(!try_grab_page(page, flags))) { + page = NULL; + goto out; + } + } else { + if (is_hugetlb_entry_migration(pte)) { + spin_unlock(ptl); + __migration_entry_wait(mm, (pte_t *)pud, ptl); + goto retry; + } + } +out: + spin_unlock(ptl); + return page; } struct page * __weak -- 2.25.1