btrfs: cow_file_range() num_bytes and disk_num_bytes are same

BugLink: https://bugs.launchpad.net/bugs/1887011

[ Upstream commit 3752d22f ]

This patch deletes local variable disk_num_bytes as its value
is same as num_bytes in the function cow_file_range().
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Kelsey Skunberg <kelsey.skunberg@canonical.com>

fs/btrfs/inode.c

@@ -926,7 +926,6 @@ static noinline int cow_file_range(struct inode *inode,
 	u64 alloc_hint = 0;
 	u64 num_bytes;
 	unsigned long ram_size;
-	u64 disk_num_bytes;
 	u64 cur_alloc_size;
 	u64 blocksize = root->sectorsize;
 	struct btrfs_key ins;
@@ -942,7 +941,6 @@ static noinline int cow_file_range(struct inode *inode,
 
 	num_bytes = ALIGN(end - start + 1, blocksize);
 	num_bytes = max(blocksize,  num_bytes);
-	disk_num_bytes = num_bytes;
 
 	/* if this is a small write inside eof, kick off defrag */
 	if (num_bytes < 64 * 1024 &&
@@ -969,16 +967,15 @@ static noinline int cow_file_range(struct inode *inode,
 		}
 	}
 
-	BUG_ON(disk_num_bytes >
-	       btrfs_super_total_bytes(root->fs_info->super_copy));
+	BUG_ON(num_bytes > btrfs_super_total_bytes(root->fs_info->super_copy));
 
 	alloc_hint = get_extent_allocation_hint(inode, start, num_bytes);
 	btrfs_drop_extent_cache(inode, start, start + num_bytes - 1, 0);
 
-	while (disk_num_bytes > 0) {
+	while (num_bytes > 0) {
 		unsigned long op;
 
-		cur_alloc_size = disk_num_bytes;
+		cur_alloc_size = num_bytes;
 		ret = btrfs_reserve_extent(root, cur_alloc_size,
 					   root->sectorsize, 0, alloc_hint,
 					   &ins, 1, 1);
@@ -1033,7 +1030,7 @@ static noinline int cow_file_range(struct inode *inode,
 				goto out_drop_extent_cache;
 		}
 
-		if (disk_num_bytes < cur_alloc_size)
+		if (num_bytes < cur_alloc_size)
 			break;
 
 		/* we're not doing compressed IO, don't unlock the first
@@ -1050,8 +1047,10 @@ static noinline int cow_file_range(struct inode *inode,
 					     start + ram_size - 1, locked_page,
 					     EXTENT_LOCKED | EXTENT_DELALLOC,
 					     op);
-		disk_num_bytes -= cur_alloc_size;
-		num_bytes -= cur_alloc_size;
+		if (num_bytes < cur_alloc_size)
+			num_bytes = 0;
+		else
+			num_bytes -= cur_alloc_size;
 		alloc_hint = ins.objectid + ins.offset;
 		start += cur_alloc_size;
 	}