xfs: refactor domain and refcount checking

Create a helper function to ensure that CoW staging extent records have
a single refcount and that shared extent records have more than 1
refcount.  We'll put this to more use in the next patch.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

fs/xfs/libxfs/xfs_refcount.c

@@ -142,10 +142,7 @@ xfs_refcount_get_rec(
 	if (irec->rc_blockcount == 0 || irec->rc_blockcount > MAXREFCEXTLEN)
 		goto out_bad_rec;
 
-	/* handle special COW-staging domain */
-	if (irec->rc_domain == XFS_REFC_DOMAIN_COW && irec->rc_refcount != 1)
-		goto out_bad_rec;
-	if (irec->rc_domain == XFS_REFC_DOMAIN_SHARED && irec->rc_refcount < 2)
+	if (!xfs_refcount_check_domain(irec))
 		goto out_bad_rec;
 
 	/* check for valid extent range, including overflow */

fs/xfs/libxfs/xfs_refcount.h

@@ -55,6 +55,18 @@ struct xfs_refcount_intent {
 	xfs_fsblock_t				ri_startblock;
 };
 
+/* Check that the refcount is appropriate for the record domain. */
+static inline bool
+xfs_refcount_check_domain(
+	const struct xfs_refcount_irec	*irec)
+{
+	if (irec->rc_domain == XFS_REFC_DOMAIN_COW && irec->rc_refcount != 1)
+		return false;
+	if (irec->rc_domain == XFS_REFC_DOMAIN_SHARED && irec->rc_refcount < 2)
+		return false;
+	return true;
+}
+
 void xfs_refcount_increase_extent(struct xfs_trans *tp,
 		struct xfs_bmbt_irec *irec);
 void xfs_refcount_decrease_extent(struct xfs_trans *tp,

fs/xfs/scrub/refcount.c

@@ -337,14 +337,12 @@ xchk_refcountbt_rec(
 
 	xfs_refcount_btrec_to_irec(rec, &irec);
 
-	/* Only CoW records can have refcount == 1. */
-	if (irec.rc_domain == XFS_REFC_DOMAIN_SHARED && irec.rc_refcount == 1)
+	/* Check the domain and refcount are not incompatible. */
+	if (!xfs_refcount_check_domain(&irec))
 		xchk_btree_set_corrupt(bs->sc, bs->cur, 0);
-	if (irec.rc_domain == XFS_REFC_DOMAIN_COW) {
-		if (irec.rc_refcount != 1)
-			xchk_btree_set_corrupt(bs->sc, bs->cur, 0);
+
+	if (irec.rc_domain == XFS_REFC_DOMAIN_COW)
 		(*cow_blocks) += irec.rc_blockcount;
-	}
 
 	/* Check the extent. */
 	if (!xfs_verify_agbext(pag, irec.rc_startblock, irec.rc_blockcount))