btrfs: change return type of btrfs_page_mkwrite to vm_fault_t

Use the new return type vm_fault_t for fault handler. For now, this is
just documenting that the function returns a VM_FAULT value rather than
an errno. Once all instances are converted, vm_fault_t will become a
distinct type.

Reference commit 1c8f422059 ("mm: change return type to vm_fault_t")

vmf_error() is the newly introduced inline function in 4.17-rc6.

Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/ctree.h

@@ -3197,7 +3197,7 @@ int btrfs_merge_bio_hook(struct page *page, unsigned long offset,
 			 size_t size, struct bio *bio,
 			 unsigned long bio_flags);
 void btrfs_set_range_writeback(void *private_data, u64 start, u64 end);
-int btrfs_page_mkwrite(struct vm_fault *vmf);
+vm_fault_t btrfs_page_mkwrite(struct vm_fault *vmf);
 int btrfs_readpage(struct file *file, struct page *page);
 void btrfs_evict_inode(struct inode *inode);
 int btrfs_write_inode(struct inode *inode, struct writeback_control *wbc);

fs/btrfs/inode.c

@@ -8872,7 +8872,7 @@ again:
  * beyond EOF, then the page is guaranteed safe against truncation until we
  * unlock the page.
  */
-int btrfs_page_mkwrite(struct vm_fault *vmf)
+vm_fault_t btrfs_page_mkwrite(struct vm_fault *vmf)
 {
 	struct page *page = vmf->page;
 	struct inode *inode = file_inode(vmf->vma->vm_file);
@@ -8884,7 +8884,8 @@ int btrfs_page_mkwrite(struct vm_fault *vmf)
 	char *kaddr;
 	unsigned long zero_start;
 	loff_t size;
-	int ret;
+	vm_fault_t ret;
+	int ret2;
 	int reserved = 0;
 	u64 reserved_space;
 	u64 page_start;
@@ -8906,17 +8907,14 @@ int btrfs_page_mkwrite(struct vm_fault *vmf)
 	 * end up waiting indefinitely to get a lock on the page currently
 	 * being processed by btrfs_page_mkwrite() function.
 	 */
-	ret = btrfs_delalloc_reserve_space(inode, &data_reserved, page_start,
+	ret2 = btrfs_delalloc_reserve_space(inode, &data_reserved, page_start,
 					   reserved_space);
-	if (!ret) {
-		ret = file_update_time(vmf->vma->vm_file);
+	if (!ret2) {
+		ret2 = file_update_time(vmf->vma->vm_file);
 		reserved = 1;
 	}
-	if (ret) {
-		if (ret == -ENOMEM)
-			ret = VM_FAULT_OOM;
-		else /* -ENOSPC, -EIO, etc */
-			ret = VM_FAULT_SIGBUS;
+	if (ret2) {
+		ret = vmf_error(ret2);
 		if (reserved)
 			goto out;
 		goto out_noreserve;
@@ -8975,15 +8973,15 @@ again:
 			  EXTENT_DO_ACCOUNTING | EXTENT_DEFRAG,
 			  0, 0, &cached_state);
 
-	ret = btrfs_set_extent_delalloc(inode, page_start, end, 0,
+	ret2 = btrfs_set_extent_delalloc(inode, page_start, end, 0,
 					&cached_state, 0);
-	if (ret) {
+	if (ret2) {
 		unlock_extent_cached(io_tree, page_start, page_end,
 				     &cached_state);
 		ret = VM_FAULT_SIGBUS;
 		goto out_unlock;
 	}
-	ret = 0;
+	ret2 = 0;
 
 	/* page is wholly or partially inside EOF */
 	if (page_start + PAGE_SIZE > size)
@@ -9008,7 +9006,7 @@ again:
 	unlock_extent_cached(io_tree, page_start, page_end, &cached_state);
 
 out_unlock:
-	if (!ret) {
+	if (!ret2) {
 		btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE, true);
 		sb_end_pagefault(inode->i_sb);
 		extent_changeset_free(data_reserved);