| Message ID | 20170126115819.58875-7-kirill.shutemov@linux.intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, Jan 26, 2017 at 02:57:48PM +0300, Kirill A. Shutemov wrote: > 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. ... of course, the filesystem could implement ->pmd_fault, and then it wouldn't hit this case ... -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, Jan 26, 2017 at 07:44:39AM -0800, Matthew Wilcox wrote: > On Thu, Jan 26, 2017 at 02:57:48PM +0300, Kirill A. Shutemov wrote: > > 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. > > ... of course, the filesystem could implement ->pmd_fault, and then it > wouldn't hit this case ... I would rather get rid of ->pmd_fault/->huge_fault :) ->fault should be flexible enough to provide for all of them...
On Thu, Jan 26, 2017 at 02:57:48PM +0300, Kirill A. Shutemov wrote: > 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 <kirill.shutemov@linux.intel.com> > Reviewed-by: Jan Kara <jack@suse.cz> Reviewed-by: Matthew Wilcox <mawilcox@microsoft.com>
diff --git a/mm/memory.c b/mm/memory.c index 6bf2b471e30c..903d9d3e01c0 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3488,8 +3488,16 @@ 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;