xfs: remove xfs_buf.b_offset

b_offset is only set for slab backed buffers and always set to
offset_in_page(bp->b_addr), which can be done just as easily in the only
user of b_offset.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>

Author: Christoph Hellwig

fs/xfs/xfs_buf.c

@@ -278,7 +278,6 @@ xfs_buf_alloc_kmem(
 		bp->b_addr = NULL;
 		return -ENOMEM;
 	}
-	bp->b_offset = offset_in_page(bp->b_addr);
 	bp->b_pages = bp->b_page_array;
 	bp->b_pages[0] = kmem_to_page(bp->b_addr);
 	bp->b_page_count = 1;
@@ -1474,7 +1473,7 @@ xfs_buf_submit_bio(
 
 	if (bp->b_flags & _XBF_KMEM) {
 		__bio_add_page(bio, virt_to_page(bp->b_addr), size,
-				bp->b_offset);
+				offset_in_page(bp->b_addr));
 	} else {
 		for (p = 0; p < bp->b_page_count; p++)
 			__bio_add_page(bio, bp->b_pages[p], PAGE_SIZE, 0);

fs/xfs/xfs_buf.h

@@ -194,8 +194,6 @@ struct xfs_buf {
 	int			b_map_count;
 	atomic_t		b_pin_count;	/* pin count */
 	unsigned int		b_page_count;	/* size of page array */
-	unsigned int		b_offset;	/* page offset of b_addr,
-						   only for _XBF_KMEM buffers */
 	int			b_error;	/* error code on I/O */
 	void			(*b_iodone)(struct xfs_buf *bp);