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From: Muchun Song In-Reply-To: <2343da2e-f91f-4861-bb22-28f77db98c52@bytedance.com> Date: Tue, 24 Sep 2024 16:52:34 +0800 Cc: david@redhat.com, hughd@google.com, willy@infradead.org, vbabka@kernel.org, akpm@linux-foundation.org, rppt@kernel.org, vishal.moola@gmail.com, peterx@redhat.com, ryan.roberts@arm.com, christophe.leroy2@cs-soprasteria.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org Content-Transfer-Encoding: quoted-printable Message-Id: <1D1872F1-7280-4F43-8213-A720C56B0646@linux.dev> References: <07d975c50fe09c246e087303b39998430b1a66bd.1727148662.git.zhengqi.arch@bytedance.com> <79699B24-0D99-4051-91F3-5695D32D62AC@linux.dev> <2343da2e-f91f-4861-bb22-28f77db98c52@bytedance.com> To: Qi Zheng X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 065CB1C0015 X-Stat-Signature: t43ansorr91jyce4hbu99c8i574c1kdb X-Rspam-User: X-HE-Tag: 1727167997-384896 X-HE-Meta: U2FsdGVkX18jHSK4dNLFkAQ5pNfBSJPXTL2E5K9GbbiH+zqjpGTzbX1ogdjk7ZvpoPxgxOj0UzjXfOZRbY5XSFuSCYkRqSlS3NxqHvgLoFMTul58GyuWmQuzw78vIHlORchqEoI6CIV4dZQqtBbCth+U60CGB9y7eilhU9d++T+UiFJEt1bLcMrqcT4l/mOqr4Sv0CoyGRBxO6melp9exCeWIXA6RUPVlur4ItMbfHTq6x9aM8RCygi9iOJxKq1E3pOCB2v7AdCQiKoHnWlGo1JlLNnejzR8/flQxgFO05MsHw7w6qrUoyKWTtg/emxDRVd/xMcJ+s82M3jpyVPvatICyFbCmNkSaTrGLkqcfDaljBZRf72Z7+caDIokkuGaq8sB0+82Vk/8Sg6BKwDez8JgtnjvzN+IPl4VRRZsD8Zq5KRU4t/91Gfi0assCycLjyg3k6SWvZ1iUIspXxwMLBEishMObQbtwL8oBLExxqJzuokpb5d0r5fQyTbnCGiRtqdMeFgzdS98N/5o9bsGidXSxoo9af31dhyLkCwrBEWiIrqCBi7u95F7I5PQW64pXYCQ2KQcDMNCyLRByo9PZwCRdOCHNHTJimhoj24wQoCBJfJABiG2z9a5mTRQVj2YJiT5FxEmBQYGLZVECx9b9uJmsvX9EOWYZhL8x+ZiV3amygCEkdl3GOBWH57JIiP0L6mq48/jOn4YYYbDRzgU7Dyqannyoj3MCYYsxFgn+XPU9Ip1GtF1bnE5toW8PGCZ590xObIWz/7ar56Pf7ZR8s+WbuOHY8poHiZWTDfIAjhtezsC6DZbJyRGs3xJmvqVokNoqojKhox4Wn7sE0C2W94jlbllqZIEBnlZyv5LTwEOfk6CPvx7UsvHsja6Lup5D4jCdA3hTZwQEwQMs6+CNXbHeG22y6L5HN0EZ4E6GmvTOEV1PUbJ/S9oqxn9FxwtQbzp6vm3Bjpf5ftewaV IXgKi/RZ yVX01FvTYntTcU0o4dpCygg1hYx7sdjR8v1nvnDiAu7mHd79HMhw1H103OTiN2+hFGdooGKiOSjZLktDRIQE8mQhFmBA/jBwsqVRqIXDWCojikvJd2KmjNPolGf6bj7kLBcYn4oijMjCzPahALgZAimey/4l60ijJbqdklljKO6QC8S2MwC72BFr5sLpeUbCHkQSFbbjCTEq4R+F/Zsla/MOBfC3zrul66dBL8VCxqoITaVlJwDBCQwnWiV/UHd10dfEka+pWG1zPaQFzKITL62WaHMtN8gy/aQLBg5+JGMoFFujHJk1MI8snBUXv+XogQPNpxs0erEGz65lho76yc3FnOq3laCdcvnfH 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: > On Sep 24, 2024, at 15:29, Qi Zheng = wrote: >=20 >=20 >=20 > On 2024/9/24 15:14, Muchun Song wrote: >>> On Sep 24, 2024, at 14:11, Qi Zheng = wrote: >>> =EF=BB=BFIn collapse_pte_mapped_thp(), we may modify the pte and pmd = entry after >>> acquring the ptl, so convert it to using pte_offset_map_rw_nolock(). = At >>> this time, the pte_same() check is not performed after the PTL held. = So we >>> should get pgt_pmd and do pmd_same() check after the ptl held. >>>=20 >>> Signed-off-by: Qi Zheng >>> --- >>> mm/khugepaged.c | 14 +++++++++++--- >>> 1 file changed, 11 insertions(+), 3 deletions(-) >>>=20 >>> diff --git a/mm/khugepaged.c b/mm/khugepaged.c >>> index 6498721d4783a..8ab79c13d077f 100644 >>> --- a/mm/khugepaged.c >>> +++ b/mm/khugepaged.c >>> @@ -1605,7 +1605,7 @@ int collapse_pte_mapped_thp(struct mm_struct = *mm, unsigned long addr, >>> if (userfaultfd_armed(vma) && !(vma->vm_flags & VM_SHARED)) >>> pml =3D pmd_lock(mm, pmd); >>>=20 >>> - start_pte =3D pte_offset_map_nolock(mm, pmd, haddr, &ptl); >>> + start_pte =3D pte_offset_map_rw_nolock(mm, pmd, haddr, = &pgt_pmd, &ptl); >>> if (!start_pte) /* mmap_lock + page lock should prevent = this */ >>> goto abort; >>> if (!pml) >>> @@ -1613,6 +1613,9 @@ int collapse_pte_mapped_thp(struct mm_struct = *mm, unsigned long addr, >>> else if (ptl !=3D pml) >>> spin_lock_nested(ptl, SINGLE_DEPTH_NESTING); >>>=20 >>> + if (unlikely(!pmd_same(pgt_pmd, pmdp_get_lockless(pmd)))) >>> + goto abort; >>> + >>> /* step 2: clear page table and adjust rmap */ >>> for (i =3D 0, addr =3D haddr, pte =3D start_pte; >>> i < HPAGE_PMD_NR; i++, addr +=3D PAGE_SIZE, pte++) { >>> @@ -1645,7 +1648,6 @@ int collapse_pte_mapped_thp(struct mm_struct = *mm, unsigned long addr, >>> nr_ptes++; >>> } >>>=20 >>> - pte_unmap(start_pte); >>> if (!pml) >>> spin_unlock(ptl); >>>=20 >>> @@ -1658,13 +1660,19 @@ int collapse_pte_mapped_thp(struct mm_struct = *mm, unsigned long addr, >>> /* step 4: remove empty page table */ >>> if (!pml) { >>> pml =3D pmd_lock(mm, pmd); >>> - if (ptl !=3D pml) >>> + if (ptl !=3D pml) { >>> spin_lock_nested(ptl, SINGLE_DEPTH_NESTING); >>> + if (unlikely(!pmd_same(pgt_pmd, = pmdp_get_lockless(pmd)))) { >>> + spin_unlock(pml); >>> + goto abort; >> Drop the reference of folio and the mm counter twice at the label of = abort and the step 3. >=20 > My bad, should set nr_ptes to 0 and call flush_tlb_mm() here, right? Or add a new label "out" just below the "abort". Then go to out. >=20 >>> + } >>> + } >>> } >>> pgt_pmd =3D pmdp_collapse_flush(vma, haddr, pmd); >>> pmdp_get_lockless_sync(); >>> if (ptl !=3D pml) >>> spin_unlock(ptl); >>> + pte_unmap(start_pte); >>> spin_unlock(pml); >> Why not? >> pte_unmap_unlock(start_pte, ptl); >> if (pml !=3D ptl) >> spin_unlock(pml); >=20 > Both are fine, will do. >=20 > Thanks, > Qi >=20 >>>=20 >>> mmu_notifier_invalidate_range_end(&range); >>> -- >>> 2.20.1