1 files changed, 20 insertions, 17 deletions

diff --git a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu.c b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu.c
index a17eea9..b079ee7 100644
--- a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu.c
+++ b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu.c
@@ -374,13 +374,11 @@ static int
 dmu_buf_hold_array_by_dnode(dnode_t *dn, uint64_t offset, uint64_t length,
     int read, void *tag, int *numbufsp, dmu_buf_t ***dbpp, uint32_t flags)
 {
-	dsl_pool_t *dp = NULL;
 	dmu_buf_t **dbp;
 	uint64_t blkid, nblks, i;
 	uint32_t dbuf_flags;
 	int err;
 	zio_t *zio;
-	hrtime_t start;
 
 	ASSERT(length <= DMU_MAX_ACCESS);
 
@@ -408,9 +406,6 @@ dmu_buf_hold_array_by_dnode(dnode_t *dn, uint64_t offset, uint64_t length,
 	}
 	dbp = kmem_zalloc(sizeof (dmu_buf_t *) * nblks, KM_SLEEP);
 
-	if (dn->dn_objset->os_dsl_dataset)
-		dp = dn->dn_objset->os_dsl_dataset->ds_dir->dd_pool;
-	start = gethrtime();
 	zio = zio_root(dn->dn_objset->os_spa, NULL, NULL, ZIO_FLAG_CANFAIL);
 	blkid = dbuf_whichblock(dn, offset);
 	for (i = 0; i < nblks; i++) {
@@ -434,9 +429,6 @@ dmu_buf_hold_array_by_dnode(dnode_t *dn, uint64_t offset, uint64_t length,
 
 	/* wait for async i/o */
 	err = zio_wait(zio);
-	/* track read overhead when we are in sync context */
-	if (dp && dsl_pool_sync_context(dp))
-		dp->dp_read_overhead += gethrtime() - start;
 	if (err) {
 		dmu_buf_rele_array(dbp, nblks, tag);
 		return (err);
@@ -518,12 +510,22 @@ dmu_buf_rele_array(dmu_buf_t **dbp_fake, int numbufs, void *tag)
 	kmem_free(dbp, sizeof (dmu_buf_t *) * numbufs);
 }
 
+/*
+ * Issue prefetch i/os for the given blocks.
+ *
+ * Note: The assumption is that we *know* these blocks will be needed
+ * almost immediately.  Therefore, the prefetch i/os will be issued at
+ * ZIO_PRIORITY_SYNC_READ
+ *
+ * Note: indirect blocks and other metadata will be read synchronously,
+ * causing this function to block if they are not already cached.
+ */
 void
 dmu_prefetch(objset_t *os, uint64_t object, uint64_t offset, uint64_t len)
 {
 	dnode_t *dn;
 	uint64_t blkid;
-	int nblks, i, err;
+	int nblks, err;
 
 	if (zfs_prefetch_disable)
 		return;
@@ -536,7 +538,7 @@ dmu_prefetch(objset_t *os, uint64_t object, uint64_t offset, uint64_t len)
 
 		rw_enter(&dn->dn_struct_rwlock, RW_READER);
 		blkid = dbuf_whichblock(dn, object * sizeof (dnode_phys_t));
-		dbuf_prefetch(dn, blkid);
+		dbuf_prefetch(dn, blkid, ZIO_PRIORITY_SYNC_READ);
 		rw_exit(&dn->dn_struct_rwlock);
 		return;
 	}
@@ -553,16 +555,16 @@ dmu_prefetch(objset_t *os, uint64_t object, uint64_t offset, uint64_t len)
 	rw_enter(&dn->dn_struct_rwlock, RW_READER);
 	if (dn->dn_datablkshift) {
 		int blkshift = dn->dn_datablkshift;
-		nblks = (P2ROUNDUP(offset+len, 1<<blkshift) -
-		    P2ALIGN(offset, 1<<blkshift)) >> blkshift;
+		nblks = (P2ROUNDUP(offset + len, 1 << blkshift) -
+		    P2ALIGN(offset, 1 << blkshift)) >> blkshift;
 	} else {
 		nblks = (offset < dn->dn_datablksz);
 	}
 
 	if (nblks != 0) {
 		blkid = dbuf_whichblock(dn, offset);
-		for (i = 0; i < nblks; i++)
-			dbuf_prefetch(dn, blkid+i);
+		for (int i = 0; i < nblks; i++)
+			dbuf_prefetch(dn, blkid + i, ZIO_PRIORITY_SYNC_READ);
 	}
 
 	rw_exit(&dn->dn_struct_rwlock);
@@ -1376,7 +1378,7 @@ dmu_sync_late_arrival(zio_t *pio, objset_t *os, dmu_sync_cb_t *done, zgd_t *zgd,
 
 	zio_nowait(zio_write(pio, os->os_spa, dmu_tx_get_txg(tx), zgd->zgd_bp,
 	    zgd->zgd_db->db_data, zgd->zgd_db->db_size, zp,
-	    dmu_sync_late_arrival_ready, dmu_sync_late_arrival_done, dsa,
+	    dmu_sync_late_arrival_ready, NULL, dmu_sync_late_arrival_done, dsa,
 	    ZIO_PRIORITY_SYNC_WRITE, ZIO_FLAG_CANFAIL, zb));
 
 	return (0);
@@ -1516,8 +1518,9 @@ dmu_sync(zio_t *pio, uint64_t txg, dmu_sync_cb_t *done, zgd_t *zgd)
 
 	zio_nowait(arc_write(pio, os->os_spa, txg,
 	    bp, dr->dt.dl.dr_data, DBUF_IS_L2CACHEABLE(db),
-	    DBUF_IS_L2COMPRESSIBLE(db), &zp, dmu_sync_ready, dmu_sync_done,
-	    dsa, ZIO_PRIORITY_SYNC_WRITE, ZIO_FLAG_CANFAIL, &zb));
+	    DBUF_IS_L2COMPRESSIBLE(db), &zp, dmu_sync_ready,
+	    NULL, dmu_sync_done, dsa, ZIO_PRIORITY_SYNC_WRITE,
+	    ZIO_FLAG_CANFAIL, &zb));
 
 	return (0);
 }