btrfs: use variable for end offset in extent_writepage_io()

[ Upstream commit 46a2390 ]

Instead of repeating the expression "start + len" multiple times, store it
in a variable and use it where needed.

Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Anand Jain <asj@kernel.org>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Stable-dep-of: e9e3b22 ("btrfs: fix beyond-EOF write handling")
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: fdmanana

fs/btrfs/extent_io.c

@@ -1691,14 +1691,15 @@ static noinline_for_stack int extent_writepage_io(struct btrfs_inode *inode,
 	unsigned long range_bitmap = 0;
 	bool submitted_io = false;
 	int found_error = 0;
+	const u64 end = start + len;
 	const u64 folio_start = folio_pos(folio);
 	const u64 folio_end = folio_start + folio_size(folio);
 	const unsigned int blocks_per_folio = btrfs_blocks_per_folio(fs_info, folio);
 	u64 cur;
 	int bit;
 	int ret = 0;
 
-	ASSERT(start >= folio_start && start + len <= folio_end);
+	ASSERT(start >= folio_start && end <= folio_end);
 
 	ret = btrfs_writepage_cow_fixup(folio);
 	if (ret == -EAGAIN) {
@@ -1714,7 +1715,7 @@ static noinline_for_stack int extent_writepage_io(struct btrfs_inode *inode,
 		return ret;
 	}
 
-	for (cur = start; cur < start + len; cur += fs_info->sectorsize)
+	for (cur = start; cur < end; cur += fs_info->sectorsize)
 		set_bit((cur - folio_start) >> fs_info->sectorsize_bits, &range_bitmap);
 	bitmap_and(&bio_ctrl->submit_bitmap, &bio_ctrl->submit_bitmap, &range_bitmap,
 		   blocks_per_folio);
@@ -1743,7 +1744,7 @@ static noinline_for_stack int extent_writepage_io(struct btrfs_inode *inode,
 			btrfs_put_ordered_extent(ordered);
 
 			btrfs_mark_ordered_io_finished(inode, folio, cur,
-						       start + len - cur, true);
+						       end - cur, true);
 			/*
 			 * This range is beyond i_size, thus we don't need to
 			 * bother writing back.
@@ -1752,8 +1753,7 @@ static noinline_for_stack int extent_writepage_io(struct btrfs_inode *inode,
 			 * writeback the sectors with subpage dirty bits,
 			 * causing writeback without ordered extent.
 			 */
-			btrfs_folio_clear_dirty(fs_info, folio, cur,
-						start + len - cur);
+			btrfs_folio_clear_dirty(fs_info, folio, cur, end - cur);
 			break;
 		}
 		ret = submit_one_sector(inode, folio, cur, bio_ctrl, i_size);