xfs: standardize ondisk to incore conversion for free space btrees

Create a xfs_alloc_btrec_to_irec function to convert an ondisk record to
an incore record, and a xfs_alloc_check_irec function to detect
corruption.  Replace all the open-coded logic with calls to the new
helpers and bubble up corruption reports.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

fs/xfs/libxfs/xfs_alloc.c

@@ -233,6 +233,34 @@ xfs_alloc_update(
 	return xfs_btree_update(cur, &rec);
 }
 
+/* Convert the ondisk btree record to its incore representation. */
+void
+xfs_alloc_btrec_to_irec(
+	const union xfs_btree_rec	*rec,
+	struct xfs_alloc_rec_incore	*irec)
+{
+	irec->ar_startblock = be32_to_cpu(rec->alloc.ar_startblock);
+	irec->ar_blockcount = be32_to_cpu(rec->alloc.ar_blockcount);
+}
+
+/* Simple checks for free space records. */
+xfs_failaddr_t
+xfs_alloc_check_irec(
+	struct xfs_btree_cur		*cur,
+	const struct xfs_alloc_rec_incore *irec)
+{
+	struct xfs_perag		*pag = cur->bc_ag.pag;
+
+	if (irec->ar_blockcount == 0)
+		return __this_address;
+
+	/* check for valid extent range, including overflow */
+	if (!xfs_verify_agbext(pag, irec->ar_startblock, irec->ar_blockcount))
+		return __this_address;
+
+	return NULL;
+}
+
 /*
  * Get the data from the pointed-to record.
  */
@@ -243,34 +271,34 @@ xfs_alloc_get_rec(
 	xfs_extlen_t		*len,	/* output: length of extent */
 	int			*stat)	/* output: success/failure */
 {
+	struct xfs_alloc_rec_incore irec;
 	struct xfs_mount	*mp = cur->bc_mp;
 	struct xfs_perag	*pag = cur->bc_ag.pag;
 	union xfs_btree_rec	*rec;
+	xfs_failaddr_t		fa;
 	int			error;
 
 	error = xfs_btree_get_rec(cur, &rec, stat);
 	if (error || !(*stat))
 		return error;
 
-	*bno = be32_to_cpu(rec->alloc.ar_startblock);
-	*len = be32_to_cpu(rec->alloc.ar_blockcount);
-
-	if (*len == 0)
-		goto out_bad_rec;
-
-	/* check for valid extent range, including overflow */
-	if (!xfs_verify_agbext(pag, *bno, *len))
+	xfs_alloc_btrec_to_irec(rec, &irec);
+	fa = xfs_alloc_check_irec(cur, &irec);
+	if (fa)
 		goto out_bad_rec;
 
+	*bno = irec.ar_startblock;
+	*len = irec.ar_blockcount;
 	return 0;
 
 out_bad_rec:
 	xfs_warn(mp,
-		"%s Freespace BTree record corruption in AG %d detected!",
+		"%s Freespace BTree record corruption in AG %d detected at %pS!",
 		cur->bc_btnum == XFS_BTNUM_BNO ? "Block" : "Size",
-		pag->pag_agno);
+		pag->pag_agno, fa);
 	xfs_warn(mp,
-		"start block 0x%x block count 0x%x", *bno, *len);
+		"start block 0x%x block count 0x%x", irec.ar_startblock,
+		irec.ar_blockcount);
 	return -EFSCORRUPTED;
 }
 
@@ -3665,8 +3693,10 @@ xfs_alloc_query_range_helper(
 	struct xfs_alloc_query_range_info	*query = priv;
 	struct xfs_alloc_rec_incore		irec;
 
-	irec.ar_startblock = be32_to_cpu(rec->alloc.ar_startblock);
-	irec.ar_blockcount = be32_to_cpu(rec->alloc.ar_blockcount);
+	xfs_alloc_btrec_to_irec(rec, &irec);
+	if (xfs_alloc_check_irec(cur, &irec) != NULL)
+		return -EFSCORRUPTED;
+
 	return query->fn(cur, &irec, query->priv);
 }
 

fs/xfs/libxfs/xfs_alloc.h

@@ -181,6 +181,12 @@ xfs_alloc_get_rec(
 	xfs_extlen_t		*len,	/* output: length of extent */
 	int			*stat);	/* output: success/failure */
 
+union xfs_btree_rec;
+void xfs_alloc_btrec_to_irec(const union xfs_btree_rec *rec,
+		struct xfs_alloc_rec_incore *irec);
+xfs_failaddr_t xfs_alloc_check_irec(struct xfs_btree_cur *cur,
+		const struct xfs_alloc_rec_incore *irec);
+
 int xfs_read_agf(struct xfs_perag *pag, struct xfs_trans *tp, int flags,
 		struct xfs_buf **agfbpp);
 int xfs_alloc_read_agf(struct xfs_perag *pag, struct xfs_trans *tp, int flags,

fs/xfs/scrub/alloc.c

@@ -78,9 +78,11 @@ xchk_allocbt_xref_other(
 STATIC void
 xchk_allocbt_xref(
 	struct xfs_scrub	*sc,
-	xfs_agblock_t		agbno,
-	xfs_extlen_t		len)
+	const struct xfs_alloc_rec_incore *irec)
 {
+	xfs_agblock_t		agbno = irec->ar_startblock;
+	xfs_extlen_t		len = irec->ar_blockcount;
+
 	if (sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)
 		return;
 
@@ -96,17 +98,15 @@ xchk_allocbt_rec(
 	struct xchk_btree		*bs,
 	const union xfs_btree_rec	*rec)
 {
-	struct xfs_perag	*pag = bs->cur->bc_ag.pag;
-	xfs_agblock_t		bno;
-	xfs_extlen_t		len;
+	struct xfs_alloc_rec_incore	irec;
 
-	bno = be32_to_cpu(rec->alloc.ar_startblock);
-	len = be32_to_cpu(rec->alloc.ar_blockcount);
-
-	if (!xfs_verify_agbext(pag, bno, len))
+	xfs_alloc_btrec_to_irec(rec, &irec);
+	if (xfs_alloc_check_irec(bs->cur, &irec) != NULL) {
 		xchk_btree_set_corrupt(bs->sc, bs->cur, 0);
+		return 0;
+	}
 
-	xchk_allocbt_xref(bs->sc, bno, len);
+	xchk_allocbt_xref(bs->sc, &irec);
 
 	return 0;
 }