From: "Kirill A. Shutemov" Subject: [PATCHv5 06/36] thp: handle write-protection faults for file THP Date: Tue, 29 Nov 2016 14:22:34 +0300 Message-ID: <20161129112304.90056-7-kirill.shutemov@linux.intel.com> References: <20161129112304.90056-1-kirill.shutemov@linux.intel.com> Cc: Alexander Viro , Hugh Dickins , Andrea Arcangeli , Dave Hansen , Vlastimil Babka , Matthew Wilcox , Ross Zwisler , linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-block@vger.kernel.org, "Kirill A. Shutemov" To: "Theodore Ts'o" , Andreas Dilger , Jan Kara , Andrew Morton Return-path: In-Reply-To: <20161129112304.90056-1-kirill.shutemov@linux.intel.com> Sender: owner-linux-mm@kvack.org List-Id: linux-ext4.vger.kernel.org For filesystems that wants to be write-notified (has mkwrite), we will encount write-protection faults for huge PMDs in shared mappings. The easiest way to handle them is to clear the PMD and let it refault as wriable. Signed-off-by: Kirill A. Shutemov Reviewed-by: Jan Kara --- mm/memory.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/mm/memory.c b/mm/memory.c index 455c3e628d52..e3d7cea8cc6a 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3495,8 +3495,16 @@ static int wp_huge_pmd(struct vm_fault *vmf, pmd_t orig_pmd) return vmf->vma->vm_ops->pmd_fault(vmf->vma, vmf->address, vmf->pmd, vmf->flags); + if (vmf->vma->vm_flags & VM_SHARED) { + /* Clear PMD */ + zap_page_range_single(vmf->vma, vmf->address & HPAGE_PMD_MASK, + HPAGE_PMD_SIZE, NULL); + + /* Refault to establish writable PMD */ + return 0; + } + /* COW handled on pte level: split pmd */ - VM_BUG_ON_VMA(vmf->vma->vm_flags & VM_SHARED, vmf->vma); __split_huge_pmd(vmf->vma, vmf->pmd, vmf->address, false, NULL); return VM_FAULT_FALLBACK; -- 2.10.2 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org