xfs: detect misaligned rtinherit directory extent size hints

If we encounter a directory that has been configured to pass on an
extent size hint to a new realtime file and the hint isn't an integer
multiple of the rt extent size, we should flag the hint for
administrative review because that is a misconfiguration (that other
parts of the kernel will fix automatically).
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

fs/xfs/scrub/inode.c

@@ -73,11 +73,25 @@ xchk_inode_extsize(
 	uint16_t		flags)
 {
 	xfs_failaddr_t		fa;
+	uint32_t		value = be32_to_cpu(dip->di_extsize);
 
-	fa = xfs_inode_validate_extsize(sc->mp, be32_to_cpu(dip->di_extsize),
-			mode, flags);
+	fa = xfs_inode_validate_extsize(sc->mp, value, mode, flags);
 	if (fa)
 		xchk_ino_set_corrupt(sc, ino);
+
+	/*
+	 * XFS allows a sysadmin to change the rt extent size when adding a rt
+	 * section to a filesystem after formatting.  If there are any
+	 * directories with extszinherit and rtinherit set, the hint could
+	 * become misaligned with the new rextsize.  The verifier doesn't check
+	 * this, because we allow rtinherit directories even without an rt
+	 * device.  Flag this as an administrative warning since we will clean
+	 * this up eventually.
+	 */
+	if ((flags & XFS_DIFLAG_RTINHERIT) &&
+	    (flags & XFS_DIFLAG_EXTSZINHERIT) &&
+	    value % sc->mp->m_sb.sb_rextsize > 0)
+		xchk_ino_set_warning(sc, ino);
 }
 
 /*