svn commit: r314280 - head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs

[Josh Paetzel]

Author: jpaetzel
Date: Sat Feb 25 20:01:17 2017
New Revision: 314280
URL: https://svnweb.freebsd.org/changeset/base/314280

Log:
  MFV 314276
  
  7570 tunable to allow zvol SCSI unmap to return on commit of txn to ZIL
  
  illumos/illumos-gate at 1c9272b861cd640a8342f4407da026ed98615517
  https://github.com/illumos/illumos-gate/commit/1c9272b861cd640a8342f4407da026ed98615517
  
  https://www.illumos.org/issues/7570
  
    Based on the discovery that every unmap waits for the commit of the txn to the ZIL,
    introducing a very high latency to unmap commands, this behavior was made into a
    tunable zvol_unmap_sync_enabled and set to false. The net impact of this change is
    that by default SCSI unmap commands will result in space being freed within the zvol
    (today they are ignored and returned with good status). However, unlike the code
    today, instead of 18+ms per unmap, they take about 30us.
  
    With the testing done on NTFS against a Win2k12 target, the new behavior should work
    seamlessly. Files on the zvol that have already been set with the zfree application
    will continue to write 0's when deleted, and any new files created since zvol
    creation will send unmap commands when deleted. This behavior exists today, but with
    this change the unmap commands will be processed and result in reclaim of space.
  
  Author: Stephen Blinick <stephen.blinick at delphix.com>
  Reviewed by: Dan Kimmel <dan.kimmel at delphix.com>
  Reviewed by: Matt Ahrens <mahrens at delphix.com>
  Reviewed by: Steve Gonczi <steve.gonczi at delphix.com>
  Reviewed by: Pavel Zakharov <pavel.zakharov at delphix.com>
  Reviewed by: Saso Kiselkov <saso.kiselkov at nexenta.com>
  Reviewed by: Yuri Pankov <yuri.pankov at nexenta.com>
  Approved by: Robert Mustacchi <rm at joyent.com>

Modified:
  head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zvol.c
Directory Properties:
  head/sys/cddl/contrib/opensolaris/   (props changed)

Modified: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zvol.c
==============================================================================
--- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zvol.c	Sat Feb 25 19:39:58 2017	(r314279)
+++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zvol.c	Sat Feb 25 20:01:17 2017	(r314280)
@@ -27,7 +27,7 @@
  * Portions Copyright 2010 Robert Milkowski
  *
  * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
- * Copyright (c) 2012, 2014 by Delphix. All rights reserved.
+ * Copyright (c) 2012, 2016 by Delphix. All rights reserved.
  * Copyright (c) 2013, Joyent, Inc. All rights reserved.
  * Copyright (c) 2014 Integros [integros.com]
  */
@@ -202,11 +202,22 @@ int zvol_maxphys = DMU_MAX_ACCESS/2;
  * Toggle unmap functionality.
  */
 boolean_t zvol_unmap_enabled = B_TRUE;
+
+/*
+ * If true, unmaps requested as synchronous are executed synchronously,
+ * otherwise all unmaps are asynchronous.
+ */
+boolean_t zvol_unmap_sync_enabled = B_FALSE;
+
 #ifndef illumos
 SYSCTL_INT(_vfs_zfs_vol, OID_AUTO, unmap_enabled, CTLFLAG_RWTUN,
     &zvol_unmap_enabled, 0,
     "Enable UNMAP functionality");
 
+SYSCTL_INT(_vfs_zfs_vol, OID_AUTO, unmap_sync_enabled, CTLFLAG_RWTUN,
+    &zvol_unmap_sync_enabled, 0,
+    "UNMAPs requested as sync are executed synchronously");
+
 static d_open_t		zvol_d_open;
 static d_close_t	zvol_d_close;
 static d_read_t		zvol_read;
@@ -2268,26 +2279,21 @@ zvol_ioctl(dev_t dev, int cmd, intptr_t 
 
 		zfs_range_unlock(rl);
 
-		if (error == 0) {
-			/*
-			 * If the write-cache is disabled or 'sync' property
-			 * is set to 'always' then treat this as a synchronous
-			 * operation (i.e. commit to zil).
-			 */
-			if (!(zv->zv_flags & ZVOL_WCE) ||
-			    (zv->zv_objset->os_sync == ZFS_SYNC_ALWAYS))
-				zil_commit(zv->zv_zilog, ZVOL_OBJ);
-
-			/*
-			 * If the caller really wants synchronous writes, and
-			 * can't wait for them, don't return until the write
-			 * is done.
-			 */
-			if (df.df_flags & DF_WAIT_SYNC) {
-				txg_wait_synced(
-				    dmu_objset_pool(zv->zv_objset), 0);
-			}
+		/*
+		 * If the write-cache is disabled, 'sync' property
+		 * is set to 'always', or if the caller is asking for
+		 * a synchronous free, commit this operation to the zil.
+		 * This will sync any previous uncommitted writes to the
+		 * zvol object.
+		 * Can be overridden by the zvol_unmap_sync_enabled tunable.
+		 */
+		if ((error == 0) && zvol_unmap_sync_enabled &&
+		    (!(zv->zv_flags & ZVOL_WCE) ||
+		    (zv->zv_objset->os_sync == ZFS_SYNC_ALWAYS) ||
+		    (df.df_flags & DF_WAIT_SYNC))) {
+			zil_commit(zv->zv_zilog, ZVOL_OBJ);
 		}
+
 		return (error);
 	}