From 7d4daf9a103b25106fcff80f1588384650c0e346 Mon Sep 17 00:00:00 2001
From: Martin Matuska <mm@FreeBSD.org>
Date: Tue, 4 May 2010 17:40:24 +0000
Subject: [PATCH] Speed up ZFS list operation with objset prefetching.

Partial import of OpenSolaris onnv revisions:
8415:8809e849f63e, 10474:0e96dd3b905a

PR:		kern/146297
Submitted by:	myself
Approved by:	pjd, delphij (mentor)
Obtained from:	OpenSolaris (Bug ID 6386929, 6755389, 6847118)
MFC after:	2 weeks
---
 .../uts/common/fs/zfs/dmu_objset.c            | 33 +++++++++++++++++++
 .../uts/common/fs/zfs/sys/dmu_objset.h        |  3 +-
 .../opensolaris/uts/common/fs/zfs/zfs_ioctl.c | 11 +++++++
 3 files changed, 45 insertions(+), 2 deletions(-)

diff --git a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_objset.c b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_objset.c
index 7981e06825c4..c9e00d511516 100644
--- a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_objset.c
+++ b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_objset.c
@@ -1213,6 +1213,39 @@ dmu_objset_find_spa(spa_t *spa, const char *name,
 	return (err);
 }
 
+/* ARGSUSED */
+int
+dmu_objset_prefetch(char *name, void *arg)
+{
+	dsl_dataset_t *ds;
+
+	if (dsl_dataset_hold(name, FTAG, &ds))
+		return (0);
+
+	if (!BP_IS_HOLE(&ds->ds_phys->ds_bp)) {
+		mutex_enter(&ds->ds_opening_lock);
+		if (!dsl_dataset_get_user_ptr(ds)) {
+			uint32_t aflags = ARC_NOWAIT | ARC_PREFETCH;
+			zbookmark_t zb;
+
+			zb.zb_objset = ds->ds_object;
+			zb.zb_object = 0;
+			zb.zb_level = -1;
+			zb.zb_blkid = 0;
+
+			(void) arc_read_nolock(NULL, dsl_dataset_get_spa(ds),
+			    &ds->ds_phys->ds_bp, NULL, NULL,
+			    ZIO_PRIORITY_ASYNC_READ,
+			    ZIO_FLAG_CANFAIL | ZIO_FLAG_SPECULATIVE,
+			    &aflags, &zb);
+		}
+		mutex_exit(&ds->ds_opening_lock);
+	}
+
+	dsl_dataset_rele(ds, FTAG);
+	return (0);
+}
+
 void
 dmu_objset_set_user(objset_t *os, void *user_ptr)
 {
diff --git a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/dmu_objset.h b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/dmu_objset.h
index 15df29a17799..1d65727808c3 100644
--- a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/dmu_objset.h
+++ b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/dmu_objset.h
@@ -26,8 +26,6 @@
 #ifndef	_SYS_DMU_OBJSET_H
 #define	_SYS_DMU_OBJSET_H
 
-#pragma ident	"%Z%%M%	%I%	%E% SMI"
-
 #include <sys/spa.h>
 #include <sys/arc.h>
 #include <sys/txg.h>
@@ -118,6 +116,7 @@ int dmu_objset_find(char *name, int func(char *, void *), void *arg,
     int flags);
 int dmu_objset_find_spa(spa_t *spa, const char *name,
     int func(spa_t *, uint64_t, const char *, void *), void *arg, int flags);
+int dmu_objset_prefetch(char *name, void *arg);
 void dmu_objset_byteswap(void *buf, size_t size);
 int dmu_objset_evict_dbufs(objset_t *os);
 
diff --git a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ioctl.c b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ioctl.c
index 00e446b82e93..1536e0b4da6c 100644
--- a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ioctl.c
+++ b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ioctl.c
@@ -1349,6 +1349,14 @@ zfs_ioc_dataset_list_next(zfs_cmd_t *zc)
 		(void) strlcat(zc->zc_name, "/", sizeof (zc->zc_name));
 	p = zc->zc_name + strlen(zc->zc_name);
 
+	if (zc->zc_cookie == 0) {
+		uint64_t cookie = 0;
+		int len = sizeof (zc->zc_name) - (p - zc->zc_name);
+
+		while (dmu_dir_list_next(os, len, p, NULL, &cookie) == 0)
+			dmu_objset_prefetch(p, NULL);
+	}
+
 	do {
 		error = dmu_dir_list_next(os,
 		    sizeof (zc->zc_name) - (p - zc->zc_name), p,
@@ -1387,6 +1395,9 @@ zfs_ioc_snapshot_list_next(zfs_cmd_t *zc)
 	objset_t *os;
 	int error;
 
+	if (zc->zc_cookie == 0)
+		dmu_objset_find(zc->zc_name, dmu_objset_prefetch,
+		    NULL, DS_FIND_SNAPSHOTS);
 	error = dmu_objset_open(zc->zc_name,
 	    DMU_OST_ANY, DS_MODE_USER | DS_MODE_READONLY, &os);
 	if (error)