[PATCH v2] fs: btrfs: Change return type to vm_fault_t

[Souptick Joarder]

Use 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.

Ref-> commit 1c8f422059ae ("mm: change return type to vm_fault_t")

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

Signed-off-by: Souptick Joarder <jrdr.linux@xxxxxxxxx>
---
v2: ret2 is the new temp variable to handle
    temporary return value within btrfs_page_mkwrite

 fs/btrfs/ctree.h |  2 +-
 fs/btrfs/inode.c | 26 ++++++++++++--------------
 2 files changed, 13 insertions(+), 15 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 0d422c9..1f52d9fd 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -3218,7 +3218,7 @@ 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);
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 0b86cf1..d9c21e0 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -8873,7 +8873,7 @@ static void btrfs_invalidatepage(struct page *page, unsigned int offset,
  * 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);
@@ -8885,8 +8885,9 @@ int btrfs_page_mkwrite(struct vm_fault *vmf)
 	char *kaddr;
 	unsigned long zero_start;
 	loff_t size;
-	int ret;
+	int ret2;
 	int reserved = 0;
+	vm_fault_t ret;
 	u64 reserved_space;
 	u64 page_start;
 	u64 page_end;
@@ -8907,17 +8908,14 @@ 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;
@@ -8976,15 +8974,15 @@ int btrfs_page_mkwrite(struct vm_fault *vmf)
 			  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)
@@ -9009,7 +9007,7 @@ int btrfs_page_mkwrite(struct vm_fault *vmf)
 	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);
-- 
1.9.1