From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: "Kirill A. Shutemov" To: "Theodore Ts'o" , Andreas Dilger , Jan Kara , Andrew Morton 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" Subject: [PATCHv2 12/41] thp: handle write-protection faults for file THP Date: Fri, 12 Aug 2016 21:37:55 +0300 Message-Id: <1471027104-115213-13-git-send-email-kirill.shutemov@linux.intel.com> In-Reply-To: <1471027104-115213-1-git-send-email-kirill.shutemov@linux.intel.com> References: <1471027104-115213-1-git-send-email-kirill.shutemov@linux.intel.com> Sender: owner-linux-mm@kvack.org List-ID: 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 --- mm/memory.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/mm/memory.c b/mm/memory.c index 4425b6059339..5b7f0ce44a27 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3448,8 +3448,17 @@ static int wp_huge_pmd(struct fault_env *fe, pmd_t orig_pmd) return fe->vma->vm_ops->pmd_fault(fe->vma, fe->address, fe->pmd, fe->flags); + if (fe->vma->vm_flags & VM_SHARED) { + /* Clear PMD */ + zap_page_range_single(fe->vma, fe->address, + HPAGE_PMD_SIZE, NULL); + VM_BUG_ON(!pmd_none(*fe->pmd)); + + /* Refault to establish writable PMD */ + return 0; + } + /* COW handled on pte level: split pmd */ - VM_BUG_ON_VMA(fe->vma->vm_flags & VM_SHARED, fe->vma); split_huge_pmd(fe->vma, fe->pmd, fe->address); return VM_FAULT_FALLBACK; -- 2.8.1 -- 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