xfs: grab the per-ag structure whenever relevant

Grab and hold the per-AG data across a scrub run whenever relevant.
This helps us avoid repeated trips through rcu and the radix tree
in the repair code.
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NDave Chinner <dchinner@redhat.com>

fs/xfs/scrub/common.c

@@ -541,6 +541,10 @@ xfs_scrub_ag_free(
 		xfs_trans_brelse(sc->tp, sa->agi_bp);
 		sa->agi_bp = NULL;
 	}
+	if (sa->pag) {
+		xfs_perag_put(sa->pag);
+		sa->pag = NULL;
+	}
 	sa->agno = NULLAGNUMBER;
 }
 
@@ -568,6 +572,19 @@ xfs_scrub_ag_init(
 	return xfs_scrub_ag_btcur_init(sc, sa);
 }
 
+/*
+ * Grab the per-ag structure if we haven't already gotten it.  Teardown of the
+ * xfs_scrub_ag will release it for us.
+ */
+void
+xfs_scrub_perag_get(
+	struct xfs_mount	*mp,
+	struct xfs_scrub_ag	*sa)
+{
+	if (!sa->pag)
+		sa->pag = xfs_perag_get(mp, sa->agno);
+}
+
 /* Per-scrubber setup functions */
 
 /*

fs/xfs/scrub/common.h

@@ -123,6 +123,7 @@ xfs_scrub_setup_quota(struct xfs_scrub_context *sc, struct xfs_inode *ip)
 void xfs_scrub_ag_free(struct xfs_scrub_context *sc, struct xfs_scrub_ag *sa);
 int xfs_scrub_ag_init(struct xfs_scrub_context *sc, xfs_agnumber_t agno,
 		      struct xfs_scrub_ag *sa);
+void xfs_scrub_perag_get(struct xfs_mount *mp, struct xfs_scrub_ag *sa);
 int xfs_scrub_ag_read_headers(struct xfs_scrub_context *sc, xfs_agnumber_t agno,
 			      struct xfs_buf **agi, struct xfs_buf **agf,
 			      struct xfs_buf **agfl);

fs/xfs/scrub/scrub.h

@@ -51,6 +51,7 @@ struct xfs_scrub_meta_ops {
 /* Buffer pointers and btree cursors for an entire AG. */
 struct xfs_scrub_ag {
 	xfs_agnumber_t			agno;
+	struct xfs_perag		*pag;
 
 	/* AG btree roots */
 	struct xfs_buf			*agf_bp;