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From: Kip Macy <kmacy@FreeBSD.org>
Date: Wed, 17 Jun 2009 20:29:56 +0000 (UTC)
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Subject: svn commit: r194396 -
	user/kmacy/releng_7_2_fcs/sys/cddl/contrib/opensolaris/uts/common/fs/zfs
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Author: kmacy
Date: Wed Jun 17 20:29:56 2009
New Revision: 194396
URL: http://svn.freebsd.org/changeset/base/194396

Log:
  don't block on pre-fetch

Modified:
  user/kmacy/releng_7_2_fcs/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_zfetch.c

Modified: user/kmacy/releng_7_2_fcs/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_zfetch.c
==============================================================================
--- user/kmacy/releng_7_2_fcs/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_zfetch.c	Wed Jun 17 20:28:07 2009	(r194395)
+++ user/kmacy/releng_7_2_fcs/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_zfetch.c	Wed Jun 17 20:29:56 2009	(r194396)
@@ -305,7 +305,10 @@ 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) {
+		rc = 1;
+		goto out;
+	}
 top:
 
 	for (zs = list_head(&zf->zf_stream); zs;