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Howlett" , Alex Sierra , Xianting Tian , Colin Cross , Suren Baghdasaryan , Barry Song , Pasha Tatashin , Suleiman Souhlal , Brian Geffon , Yu Zhao , Tong Tiangen , Liu Shixin , Li kunyu , Anshuman Khandual , Vlastimil Babka , Hugh Dickins , Minchan Kim , Miaohe Lin , Gautam Menghani , Catalin Marinas , Mark Brown , Will Deacon , "Eric W . Biederman" , Thomas Gleixner , Sebastian Andrzej Siewior , Andy Lutomirski , Fenghua Yu , Barret Rhoden , Davidlohr Bueso , "Jason A . Donenfeld" , Dinglan Peng , Pedro Fonseca , Jim Huang , Huichun Feng , Chih-En Lin Subject: [PATCH v3 07/14] mm/madvise: Handle COW-ed PTE with madvise() Date: Tue, 20 Dec 2022 15:27:36 +0800 Message-Id: <20221220072743.3039060-8-shiyn.lin@gmail.com> X-Mailer: git-send-email 2.37.3 In-Reply-To: <20221220072743.3039060-1-shiyn.lin@gmail.com> References: <20221220072743.3039060-1-shiyn.lin@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Break COW PTE if madvise() modify the pte entry of COW-ed PTE. Following are the list of flags which need to break COW PTE. However, like MADV_HUGEPAGE and MADV_MERGEABLE, we should handle it respectively. - MADV_DONTNEED: It calls to zap_page_range() which already be handled. - MADV_FREE: It uses walk_page_range() with madvise_free_pte_range() to free the page by itself, so add break_cow_pte(). - MADV_REMOVE: Same as MADV_FREE, it remove the page by itself, so add break_cow_pte_range(). - MADV_COLD: Similar to MAD_FREE, break COW PTE before pageout. - MADV_POPULATE: Let GUP deal with it. Signed-off-by: Chih-En Lin --- mm/madvise.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/mm/madvise.c b/mm/madvise.c index c7105ec6d08c0..58bccec7caa88 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -408,6 +408,9 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd, if (pmd_trans_unstable(pmd)) return 0; #endif + if (break_cow_pte(vma, pmd, addr) < 0) + return 0; + tlb_change_page_size(tlb, PAGE_SIZE); orig_pte =3D pte =3D pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); flush_tlb_batched_pending(mm); @@ -614,6 +617,10 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned= long addr, if (pmd_trans_unstable(pmd)) return 0; =20 + /* We should only allocate PTE. */ + if (break_cow_pte(vma, pmd, addr) < 0) + goto next; + tlb_change_page_size(tlb, PAGE_SIZE); orig_pte =3D pte =3D pte_offset_map_lock(mm, pmd, addr, &ptl); flush_tlb_batched_pending(mm); @@ -974,6 +981,12 @@ static long madvise_remove(struct vm_area_struct *vma, if ((vma->vm_flags & (VM_SHARED|VM_WRITE)) !=3D (VM_SHARED|VM_WRITE)) return -EACCES; =20 + error =3D break_cow_pte_range(vma, start, end); + if (error < 0) + return error; + else if (error > 0) + return -ENOMEM; + offset =3D (loff_t)(start - vma->vm_start) + ((loff_t)vma->vm_pgoff << PAGE_SHIFT); =20 --=20 2.37.3