erge tag 'libnvdimm-fixes-4.19-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm

Dan writes:
  "libnvdimm/dax for 4.19-rc6

  * (2) fixes for the dax error handling updates that were merged for
  v4.19-rc1. My mails to Al have been bouncing recently, so I do not have
  his ack but the uaccess change is of the trivial / obviously correct
  variety. The address_space_operations fixes a regression.

  * A filesystem-dax fix to correct the zero page lookup to be compatible
   with non-x86 (mips and s390) architectures."

* tag 'libnvdimm-fixes-4.19-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm:
  device-dax: Add missing address_space_operations
  uaccess: Fix is_source param for check_copy_size() in copy_to_iter_mcsafe()
  filesystem-dax: Fix use of zero page

drivers/dax/device.c

@@ -535,6 +535,11 @@ static unsigned long dax_get_unmapped_area(struct file *filp,
 	return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
 }
 
+static const struct address_space_operations dev_dax_aops = {
+	.set_page_dirty		= noop_set_page_dirty,
+	.invalidatepage		= noop_invalidatepage,
+};
+
 static int dax_open(struct inode *inode, struct file *filp)
 {
 	struct dax_device *dax_dev = inode_dax(inode);
@@ -544,6 +549,7 @@ static int dax_open(struct inode *inode, struct file *filp)
 	dev_dbg(&dev_dax->dev, "trace\n");
 	inode->i_mapping = __dax_inode->i_mapping;
 	inode->i_mapping->host = __dax_inode;
+	inode->i_mapping->a_ops = &dev_dax_aops;
 	filp->f_mapping = inode->i_mapping;
 	filp->f_wb_err = filemap_sample_wb_err(filp->f_mapping);
 	filp->private_data = dev_dax;

fs/dax.c

@@ -1120,21 +1120,12 @@ static vm_fault_t dax_load_hole(struct address_space *mapping, void *entry,
 {
 	struct inode *inode = mapping->host;
 	unsigned long vaddr = vmf->address;
-	vm_fault_t ret = VM_FAULT_NOPAGE;
-	struct page *zero_page;
-	pfn_t pfn;
-
-	zero_page = ZERO_PAGE(0);
-	if (unlikely(!zero_page)) {
-		ret = VM_FAULT_OOM;
-		goto out;
-	}
+	pfn_t pfn = pfn_to_pfn_t(my_zero_pfn(vaddr));
+	vm_fault_t ret;
 
-	pfn = page_to_pfn_t(zero_page);
 	dax_insert_mapping_entry(mapping, vmf, entry, pfn, RADIX_DAX_ZERO_PAGE,
 			false);
 	ret = vmf_insert_mixed(vmf->vma, vaddr, pfn);
-out:
 	trace_dax_load_hole(inode, vmf, ret);
 	return ret;
 }

include/linux/uio.h

@@ -172,7 +172,7 @@ size_t copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i)
 static __always_inline __must_check
 size_t copy_to_iter_mcsafe(void *addr, size_t bytes, struct iov_iter *i)
 {
-	if (unlikely(!check_copy_size(addr, bytes, false)))
+	if (unlikely(!check_copy_size(addr, bytes, true)))
 		return 0;
 	else
 		return _copy_to_iter_mcsafe(addr, bytes, i);