xfs: get rid of unnecessary xfs_perag_{get,put} pairs

In the course of some operations, we look up the perag from
the mount multiple times to get or change perag information.
These are often very short pieces of code, so while the
lookup cost is generally low, the cost of the lookup is far
higher than the cost of the operation we are doing on the
perag.

Since we changed buffers to hold references to the perag
they are cached in, many modification contexts already hold
active references to the perag that are held across these
operations. This is especially true for any operation that
is serialised by an allocation group header buffer.

In these cases, we can just use the buffer's reference to
the perag to avoid needing to do lookups to access the
perag. This means that many operations don't need to do
perag lookups at all to access the perag because they've
already looked up objects that own persistent references
and hence can use that reference instead.

Cc: Dave Chinner <dchinner@redhat.com>
Cc: "Darrick J. Wong" <darrick.wong@oracle.com>
Signed-off-by: Gao Xiang <hsiangkao@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

1 files changed, 7 insertions, 21 deletions

diff --git a/fs/xfs/libxfs/xfs_ialloc.c b/fs/xfs/libxfs/xfs_ialloc.c
index 7fcf62b324b0..f742a96a2fe1 100644
--- a/fs/xfs/libxfs/xfs_ialloc.c
+++ b/fs/xfs/libxfs/xfs_ialloc.c
@@ -888,10 +888,9 @@ sparse_alloc:
 	 */
 	be32_add_cpu(&agi->agi_count, newlen);
 	be32_add_cpu(&agi->agi_freecount, newlen);
-	pag = xfs_perag_get(args.mp, agno);
+	pag = agbp->b_pag;
 	pag->pagi_freecount += newlen;
 	pag->pagi_count += newlen;
-	xfs_perag_put(pag);
 	agi->agi_newino = cpu_to_be32(newino);
 
 	/*
@@ -1134,7 +1133,7 @@ xfs_dialloc_ag_inobt(
 	xfs_agnumber_t		agno = be32_to_cpu(agi->agi_seqno);
 	xfs_agnumber_t		pagno = XFS_INO_TO_AGNO(mp, parent);
 	xfs_agino_t		pagino = XFS_INO_TO_AGINO(mp, parent);
-	struct xfs_perag	*pag;
+	struct xfs_perag	*pag = agbp->b_pag;
 	struct xfs_btree_cur	*cur, *tcur;
 	struct xfs_inobt_rec_incore rec, trec;
 	xfs_ino_t		ino;
@@ -1143,8 +1142,6 @@ xfs_dialloc_ag_inobt(
 	int			i, j;
 	int			searchdistance = 10;
 
-	pag = xfs_perag_get(mp, agno);
-
 	ASSERT(pag->pagi_init);
 	ASSERT(pag->pagi_inodeok);
 	ASSERT(pag->pagi_freecount > 0);
@@ -1384,14 +1381,12 @@ alloc_inode:
 
 	xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
 	xfs_trans_mod_sb(tp, XFS_TRANS_SB_IFREE, -1);
-	xfs_perag_put(pag);
 	*inop = ino;
 	return 0;
 error1:
 	xfs_btree_del_cursor(tcur, XFS_BTREE_ERROR);
 error0:
 	xfs_btree_del_cursor(cur, XFS_BTREE_ERROR);
-	xfs_perag_put(pag);
 	return error;
 }
 
@@ -1587,7 +1582,6 @@ xfs_dialloc_ag(
 	xfs_agnumber_t			agno = be32_to_cpu(agi->agi_seqno);
 	xfs_agnumber_t			pagno = XFS_INO_TO_AGNO(mp, parent);
 	xfs_agino_t			pagino = XFS_INO_TO_AGINO(mp, parent);
-	struct xfs_perag		*pag;
 	struct xfs_btree_cur		*cur;	/* finobt cursor */
 	struct xfs_btree_cur		*icur;	/* inobt cursor */
 	struct xfs_inobt_rec_incore	rec;
@@ -1599,8 +1593,6 @@ xfs_dialloc_ag(
 	if (!xfs_sb_version_hasfinobt(&mp->m_sb))
 		return xfs_dialloc_ag_inobt(tp, agbp, parent, inop);
 
-	pag = xfs_perag_get(mp, agno);
-
 	/*
 	 * If pagino is 0 (this is the root inode allocation) use newino.
 	 * This must work because we've just allocated some.
@@ -1667,7 +1659,7 @@ xfs_dialloc_ag(
 	 */
 	be32_add_cpu(&agi->agi_freecount, -1);
 	xfs_ialloc_log_agi(tp, agbp, XFS_AGI_FREECOUNT);
-	pag->pagi_freecount--;
+	agbp->b_pag->pagi_freecount--;
 
 	xfs_trans_mod_sb(tp, XFS_TRANS_SB_IFREE, -1);
 
@@ -1680,7 +1672,6 @@ xfs_dialloc_ag(
 
 	xfs_btree_del_cursor(icur, XFS_BTREE_NOERROR);
 	xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
-	xfs_perag_put(pag);
 	*inop = ino;
 	return 0;
 
@@ -1688,7 +1679,6 @@ error_icur:
 	xfs_btree_del_cursor(icur, XFS_BTREE_ERROR);
 error_cur:
 	xfs_btree_del_cursor(cur, XFS_BTREE_ERROR);
-	xfs_perag_put(pag);
 	return error;
 }
 
@@ -1945,7 +1935,6 @@ xfs_difree_inobt(
 {
 	struct xfs_agi			*agi = agbp->b_addr;
 	xfs_agnumber_t			agno = be32_to_cpu(agi->agi_seqno);
-	struct xfs_perag		*pag;
 	struct xfs_btree_cur		*cur;
 	struct xfs_inobt_rec_incore	rec;
 	int				ilen;
@@ -2007,6 +1996,8 @@ xfs_difree_inobt(
 	if (!(mp->m_flags & XFS_MOUNT_IKEEP) &&
 	    rec.ir_free == XFS_INOBT_ALL_FREE &&
 	    mp->m_sb.sb_inopblock <= XFS_INODES_PER_CHUNK) {
+		struct xfs_perag	*pag = agbp->b_pag;
+
 		xic->deleted = true;
 		xic->first_ino = XFS_AGINO_TO_INO(mp, agno, rec.ir_startino);
 		xic->alloc = xfs_inobt_irec_to_allocmask(&rec);
@@ -2020,10 +2011,8 @@ xfs_difree_inobt(
 		be32_add_cpu(&agi->agi_count, -ilen);
 		be32_add_cpu(&agi->agi_freecount, -(ilen - 1));
 		xfs_ialloc_log_agi(tp, agbp, XFS_AGI_COUNT | XFS_AGI_FREECOUNT);
-		pag = xfs_perag_get(mp, agno);
 		pag->pagi_freecount -= ilen - 1;
 		pag->pagi_count -= ilen;
-		xfs_perag_put(pag);
 		xfs_trans_mod_sb(tp, XFS_TRANS_SB_ICOUNT, -ilen);
 		xfs_trans_mod_sb(tp, XFS_TRANS_SB_IFREE, -(ilen - 1));
 
@@ -2049,9 +2038,7 @@ xfs_difree_inobt(
 		 */
 		be32_add_cpu(&agi->agi_freecount, 1);
 		xfs_ialloc_log_agi(tp, agbp, XFS_AGI_FREECOUNT);
-		pag = xfs_perag_get(mp, agno);
-		pag->pagi_freecount++;
-		xfs_perag_put(pag);
+		agbp->b_pag->pagi_freecount++;
 		xfs_trans_mod_sb(tp, XFS_TRANS_SB_IFREE, 1);
 	}
 
@@ -2661,7 +2648,7 @@ xfs_ialloc_read_agi(
 		return error;
 
 	agi = (*bpp)->b_addr;
-	pag = xfs_perag_get(mp, agno);
+	pag = (*bpp)->b_pag;
 	if (!pag->pagi_init) {
 		pag->pagi_freecount = be32_to_cpu(agi->agi_freecount);
 		pag->pagi_count = be32_to_cpu(agi->agi_count);
@@ -2674,7 +2661,6 @@ xfs_ialloc_read_agi(
 	 */
 	ASSERT(pag->pagi_freecount == be32_to_cpu(agi->agi_freecount) ||
 		XFS_FORCED_SHUTDOWN(mp));
-	xfs_perag_put(pag);
 	return 0;
 }