From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:36976 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751217AbdAQJnW (ORCPT ); Tue, 17 Jan 2017 04:43:22 -0500 Subject: Patch "mm: pmd dirty emulation in page fault handler" has been added to the 4.9-stable tree To: minchan@kernel.org, akpm@linux-foundation.org, catalin.marinas@arm.com, gregkh@linuxfoundation.org, je@fb.com, kirill.shutemov@linux.intel.com, mhocko@suse.com, schwab@suse.de, torvalds@linux-foundation.org, will.deacon@arm.com Cc: , From: Date: Tue, 17 Jan 2017 10:42:47 +0100 Message-ID: <148464616768218@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled mm: pmd dirty emulation in page fault handler to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: mm-pmd-dirty-emulation-in-page-fault-handler.patch and it can be found in the queue-4.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From 20f664aabeb88d582b623a625f83b0454fa34f07 Mon Sep 17 00:00:00 2001 From: Minchan Kim Date: Tue, 10 Jan 2017 16:57:51 -0800 Subject: mm: pmd dirty emulation in page fault handler From: Minchan Kim commit 20f664aabeb88d582b623a625f83b0454fa34f07 upstream. Andreas reported [1] made a test in jemalloc hang in THP mode in arm64: http://lkml.kernel.org/r/mvmmvfy37g1.fsf@hawking.suse.de The problem is currently page fault handler doesn't supports dirty bit emulation of pmd for non-HW dirty-bit architecture so that application stucks until VM marked the pmd dirty. How the emulation work depends on the architecture. In case of arm64, when it set up pte firstly, it sets pte PTE_RDONLY to get a chance to mark the pte dirty via triggering page fault when store access happens. Once the page fault occurs, VM marks the pmd dirty and arch code for setting pmd will clear PTE_RDONLY for application to proceed. IOW, if VM doesn't mark the pmd dirty, application hangs forever by repeated fault(i.e., store op but the pmd is PTE_RDONLY). This patch enables pmd dirty-bit emulation for those architectures. [1] b8d3c4c3009d, mm/huge_memory.c: don't split THP page when MADV_FREE syscall is called Fixes: b8d3c4c3009d ("mm/huge_memory.c: don't split THP page when MADV_FREE syscall is called") Link: http://lkml.kernel.org/r/1482506098-6149-1-git-send-email-minchan@kernel.org Signed-off-by: Minchan Kim Reported-by: Andreas Schwab Tested-by: Andreas Schwab Acked-by: Kirill A. Shutemov Acked-by: Michal Hocko Cc: Jason Evans Cc: Will Deacon Cc: Catalin Marinas Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/huge_memory.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -872,15 +872,17 @@ void huge_pmd_set_accessed(struct fault_ { pmd_t entry; unsigned long haddr; + bool write = fe->flags & FAULT_FLAG_WRITE; fe->ptl = pmd_lock(fe->vma->vm_mm, fe->pmd); if (unlikely(!pmd_same(*fe->pmd, orig_pmd))) goto unlock; entry = pmd_mkyoung(orig_pmd); + if (write) + entry = pmd_mkdirty(entry); haddr = fe->address & HPAGE_PMD_MASK; - if (pmdp_set_access_flags(fe->vma, haddr, fe->pmd, entry, - fe->flags & FAULT_FLAG_WRITE)) + if (pmdp_set_access_flags(fe->vma, haddr, fe->pmd, entry, write)) update_mmu_cache_pmd(fe->vma, fe->address, fe->pmd); unlock: Patches currently in stable-queue which might be from minchan@kernel.org are queue-4.9/zram-support-bdi_cap_stable_writes.patch queue-4.9/zram-revalidate-disk-under-init_lock.patch queue-4.9/mm-pmd-dirty-emulation-in-page-fault-handler.patch