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From: Kip Macy <kmacy@FreeBSD.org>
Date: Mon, 31 Aug 2009 20:59:23 +0000 (UTC)
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Cc: 
Subject: svn commit: r196713 -
	user/kmacy/head_zfs_merge/sys/cddl/contrib/opensolaris/uts/common/fs/zfs
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Author: kmacy
Date: Mon Aug 31 20:59:23 2009
New Revision: 196713
URL: http://svn.freebsd.org/changeset/base/196713

Log:
  don't block waiting on a zfetch

Modified:
  user/kmacy/head_zfs_merge/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_zfetch.c

Modified: user/kmacy/head_zfs_merge/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_zfetch.c
==============================================================================
--- user/kmacy/head_zfs_merge/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_zfetch.c	Mon Aug 31 20:53:01 2009	(r196712)
+++ user/kmacy/head_zfs_merge/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_zfetch.c	Mon Aug 31 20:59:23 2009	(r196713)
@@ -304,7 +304,9 @@ dmu_zfetch_find(zfetch_t *zf, zstream_t 
 	 * modified in a number of different ways.
 	 */
 
-	rw_enter(&zf->zf_rwlock, RW_READER);
+	if (rw_tryenter(&zf->zf_rwlock, RW_READER) == 0)
+		return (1);
+
 top:
 
 	for (zs = list_head(&zf->zf_stream); zs;