On Wed 23-08-17 11:37:14, Christoph Hellwig wrote:

quoted

+	pfn_t pfn;
 
 	if (write) {
 		sb_start_pagefault(sb);

@@ -287,16 +288,39 @@ static int ext4_dax_huge_fault(struct vm_fault *vmf,
 		down_read(&EXT4_I(inode)->i_mmap_sem);
 		handle = ext4_journal_start_sb(sb, EXT4_HT_WRITE_PAGE,
 					       EXT4_DATA_TRANS_BLOCKS(sb));
+		if (IS_ERR(handle)) {
+			up_read(&EXT4_I(inode)->i_mmap_sem);
+			sb_end_pagefault(sb);
+			return VM_FAULT_SIGBUS;
+		}
 	} else {
 		down_read(&EXT4_I(inode)->i_mmap_sem);
 	}
-	if (!IS_ERR(handle))
-		result = dax_iomap_fault(vmf, pe_size, &ext4_iomap_ops, NULL);
-	else
-		result = VM_FAULT_SIGBUS;
+	result = dax_iomap_fault(vmf, pe_size, &ext4_iomap_ops, &pfn);

Maybe split the error handling refactor into a simple prep patch to
make this one more readable?

OK, will do.

quoted

+		/* Write fault but PFN mapped only RO? */
+		if (result & VM_FAULT_NEEDDSYNC) {
+			int err;
+			loff_t start = ((loff_t)vmf->pgoff) << PAGE_SHIFT;
+			size_t len = 0;
+
+			if (pe_size == PE_SIZE_PTE)
+				len = PAGE_SIZE;
+#ifdef CONFIG_FS_DAX_PMD
+			else if (pe_size == PE_SIZE_PMD)
+				len = HPAGE_PMD_SIZE;
+#endif
+			else
+				WARN_ON_ONCE(1);
+			err = vfs_fsync_range(vmf->vma->vm_file, start,
+					      start + len - 1, 1);
+			if (err)
+				result = VM_FAULT_SIGBUS;
+			else
+				result = dax_insert_pfn_mkwrite(vmf, pe_size,
+								pfn);
+		}

I think this needs to become a helper exported from the DAX code,
way too much magic inside the file system as-is.

Good point, there isn't anything fs specific in there.

								Honza

-- 
Jan Kara [off-list ref]
SUSE Labs, CR