md: Fix bitmap offset type in sb writer

Bitmap offset is allowed to be negative, indicating that bitmap precedes
metadata. Change the type back from sector_t to loff_t to satisfy
conditionals and calculations.
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://lore.kernel.org/linux-raid/CAPhsuW6HuaUJ5WcyPajVgUfkQFYp2D_cy1g6qxN4CU_gP2=z7g@mail.gmail.com/
Fixes: 10172f20 ("md: Fix types in sb writer")
Signed-off-by: Jonathan Derrick <jonathan.derrick@linux.dev>
Suggested-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20230425011438.71046-1-jonathan.derrick@linux.dev

drivers/md/md-bitmap.c

@@ -219,7 +219,7 @@ static unsigned int optimal_io_size(struct block_device *bdev,
 }
 
 static unsigned int bitmap_io_size(unsigned int io_size, unsigned int opt_size,
-				   sector_t start, sector_t boundary)
+				   loff_t start, loff_t boundary)
 {
 	if (io_size != opt_size &&
 	    start + opt_size / SECTOR_SIZE <= boundary)
@@ -237,8 +237,8 @@ static int __write_sb_page(struct md_rdev *rdev, struct bitmap *bitmap,
 	struct block_device *bdev;
 	struct mddev *mddev = bitmap->mddev;
 	struct bitmap_storage *store = &bitmap->storage;
-	sector_t offset = mddev->bitmap_info.offset;
-	sector_t ps, sboff, doff;
+	loff_t sboff, offset = mddev->bitmap_info.offset;
+	sector_t ps, doff;
 	unsigned int size = PAGE_SIZE;
 	unsigned int opt_size = PAGE_SIZE;