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From: Andriy Gapon <avg@FreeBSD.org>
Date: Wed, 13 Jul 2016 09:21:41 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r302728 -
 stable/9/sys/cddl/contrib/opensolaris/uts/common/fs/zfs
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Author: avg
Date: Wed Jul 13 09:21:40 2016
New Revision: 302728
URL: https://svnweb.freebsd.org/changeset/base/302728

Log:
  MFC r302123: fix deadlock-prone code in getzfsvfs()

Modified:
  stable/9/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ioctl.c
Directory Properties:
  stable/9/sys/   (props changed)
  stable/9/sys/cddl/contrib/opensolaris/   (props changed)

Modified: stable/9/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ioctl.c
==============================================================================
--- stable/9/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ioctl.c	Wed Jul 13 09:21:28 2016	(r302727)
+++ stable/9/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ioctl.c	Wed Jul 13 09:21:40 2016	(r302728)
@@ -1428,6 +1428,7 @@ static int
 getzfsvfs(const char *dsname, zfsvfs_t **zfvp)
 {
 	objset_t *os;
+	vfs_t *vfsp;
 	int error;
 
 	error = dmu_objset_hold(dsname, FTAG, &os);
@@ -1441,19 +1442,21 @@ getzfsvfs(const char *dsname, zfsvfs_t *
 	mutex_enter(&os->os_user_ptr_lock);
 	*zfvp = dmu_objset_get_user(os);
 	if (*zfvp) {
-#ifdef illumos
-		VFS_HOLD((*zfvp)->z_vfs);
-#else
-		if (vfs_busy((*zfvp)->z_vfs, 0) != 0) {
-			*zfvp = NULL;
-			error = SET_ERROR(ESRCH);
-		}
-#endif
+		vfsp = (*zfvp)->z_vfs;
+		vfs_ref(vfsp);
 	} else {
 		error = SET_ERROR(ESRCH);
 	}
 	mutex_exit(&os->os_user_ptr_lock);
 	dmu_objset_rele(os, FTAG);
+	if (error == 0) {
+		error = vfs_busy(vfsp, 0);
+		vfs_rel(vfsp);
+		if (error != 0) {
+			*zfvp = NULL;
+			error = SET_ERROR(ESRCH);
+		}
+	}
 	return (error);
 }