xfs: report larger dio alignment for COW inodes

For I/O to reflinked blocks we always need to write an entire new file
system block, and the code enforces the file system block alignment for
the entire file if it has any reflinked blocks.  Mirror the larger
value reported in the statx in the dio_offset_align in the xfs-specific
XFS_IOC_DIOINFO ioctl for the same reason.

Don't bother adding a new field for the read alignment to this legacy
ioctl as all new users should use statx instead.

Signed-off-by: Christoph Hellwig <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Reviewed-by: Darrick J. Wong <[email protected]>
Signed-off-by: Christian Brauner <[email protected]>

Author: Christoph Hellwig

fs/xfs/xfs_ioctl.c

@@ -1204,7 +1204,16 @@ xfs_file_ioctl(
 		struct xfs_buftarg	*target = xfs_inode_buftarg(ip);
 		struct dioattr		da;
 
-		da.d_mem =  da.d_miniosz = target->bt_logical_sectorsize;
+		da.d_mem = target->bt_logical_sectorsize;
+
+		/*
+		 * See xfs_report_dioalign() for an explanation about why this
+		 * reports a value larger than the sector size for COW inodes.
+		 */
+		if (xfs_is_cow_inode(ip))
+			da.d_miniosz = xfs_inode_alloc_unitsize(ip);
+		else
+			da.d_miniosz = target->bt_logical_sectorsize;
 		da.d_maxiosz = INT_MAX & ~(da.d_miniosz - 1);
 
 		if (copy_to_user(arg, &da, sizeof(da)))