[PATCHv5 06/36] thp: handle write-protection faults for file THP
From: Kirill A. Shutemov <hidden>
Date: 2016-11-29 11:22:34
Also in:
linux-ext4, linux-fsdevel, linux-mm, lkml
Subsystem:
memory management, memory management - core, the rest · Maintainers:
Andrew Morton, David Hildenbrand, Linus Torvalds
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 <redacted> Reviewed-by: Jan Kara <jack@suse.cz> --- 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