zvol: allow rename of in use ZVOL dataset

While ZFS allow renaming of in use ZVOLs at the DSL level without issues
the ZVOL layer does not correctly update the renamed dataset if the
device node is open (zv->zv_open_count > 0): trying to access the stale
dataset name, for instance during a zfs receive, will cause the
following failure:

VERIFY3(zv->zv_objset->os_dsl_dataset->ds_owner == zv) failed ((null) == ffff8800dbb6fc00)
PANIC at zvol.c:1255:zvol_resume()
Showing stack for process 1390
CPU: 0 PID: 1390 Comm: zfs Tainted: P           O  3.16.0-4-amd64 #1 Debian 3.16.51-3
Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
 0000000000000000 ffffffff8151ea00 ffffffffa0758a80 ffff88028aefba30
 ffffffffa0417219 ffff880037179220 ffffffff00000030 ffff88028aefba40
 ffff88028aefb9e0 2833594649524556 6f5f767a3e2d767a 6f3e2d7465736a62
Call Trace:
 [<0>] ? dump_stack+0x5d/0x78
 [<0>] ? spl_panic+0xc9/0x110 [spl]
 [<0>] ? mutex_lock+0xe/0x2a
 [<0>] ? zfs_refcount_remove_many+0x1ad/0x250 [zfs]
 [<0>] ? rrw_exit+0xc8/0x2e0 [zfs]
 [<0>] ? mutex_lock+0xe/0x2a
 [<0>] ? dmu_objset_from_ds+0x9a/0x250 [zfs]
 [<0>] ? dmu_objset_hold_flags+0x71/0xc0 [zfs]
 [<0>] ? zvol_resume+0x178/0x280 [zfs]
 [<0>] ? zfs_ioc_recv_impl+0x88b/0xf80 [zfs]
 [<0>] ? zfs_refcount_remove_many+0x1ad/0x250 [zfs]
 [<0>] ? zfs_ioc_recv+0x1c2/0x2a0 [zfs]
 [<0>] ? dmu_buf_get_user+0x13/0x20 [zfs]
 [<0>] ? __alloc_pages_nodemask+0x166/0xb50
 [<0>] ? zfsdev_ioctl+0x896/0x9c0 [zfs]
 [<0>] ? handle_mm_fault+0x464/0x1140
 [<0>] ? do_vfs_ioctl+0x2cf/0x4b0
 [<0>] ? __do_page_fault+0x177/0x410
 [<0>] ? SyS_ioctl+0x81/0xa0
 [<0>] ? async_page_fault+0x28/0x30
 [<0>] ? system_call_fast_compare_end+0x10/0x15

Reviewed by: Tom Caputi <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: loli10K <[email protected]>
Closes openzfs#6263 
Closes openzfs#8371

module/zfs/zvol.c

@@ -2262,12 +2262,6 @@ zvol_rename_minors_impl(const char *oldname, const char *newname)
 
 		mutex_enter(&zv->zv_state_lock);
 
-		/* If in use, leave alone */
-		if (zv->zv_open_count > 0) {
-			mutex_exit(&zv->zv_state_lock);
-			continue;
-		}
-
 		if (strcmp(zv->zv_name, oldname) == 0) {
 			zvol_rename_minor(zv, newname);
 		} else if (strncmp(zv->zv_name, oldname, oldnamelen) == 0 &&

tests/runfiles/linux.run

@@ -888,8 +888,8 @@ tags = ['functional', 'zvol', 'zvol_cli']
 [tests/functional/zvol/zvol_misc]
 tests = ['zvol_misc_001_neg', 'zvol_misc_002_pos', 'zvol_misc_003_neg',
     'zvol_misc_004_pos', 'zvol_misc_005_neg', 'zvol_misc_006_pos',
-    'zvol_misc_hierarchy', 'zvol_misc_snapdev', 'zvol_misc_volmode',
-    'zvol_misc_zil']
+    'zvol_misc_hierarchy', 'zvol_misc_rename_inuse', 'zvol_misc_snapdev',
+    'zvol_misc_volmode', 'zvol_misc_zil']
 tags = ['functional', 'zvol', 'zvol_misc']
 
 [tests/functional/zvol/zvol_swap]

tests/zfs-tests/tests/functional/zvol/zvol_misc/Makefile.am

@@ -9,6 +9,7 @@ dist_pkgdata_SCRIPTS = \
 	zvol_misc_005_neg.ksh \
 	zvol_misc_006_pos.ksh \
 	zvol_misc_hierarchy.ksh \
+	zvol_misc_rename_inuse.ksh \
 	zvol_misc_snapdev.ksh \
 	zvol_misc_volmode.ksh \
 	zvol_misc_zil.ksh

tests/zfs-tests/tests/functional/zvol/zvol_misc/cleanup.ksh

@@ -36,4 +36,6 @@ verify_runnable "global"
 
 default_zvol_cleanup
 
+[[ -d $TESTDIR ]] && rm -rf $TESTDIR
+
 log_pass

tests/zfs-tests/tests/functional/zvol/zvol_misc/setup.ksh

@@ -36,4 +36,6 @@ verify_runnable "global"
 
 default_zvol_setup $DISK $VOLSIZE
 
+log_must mkdir $TESTDIR
+
 log_pass

tests/zfs-tests/tests/functional/zvol/zvol_misc/zvol_misc_002_pos.ksh

@@ -54,7 +54,6 @@ function cleanup
 	ismounted $TESTDIR $NEWFS_DEFAULT_FS
 	(( $? == 0 )) && log_must umount $TESTDIR
 
-	[[ -e $TESTDIR ]] && rm -rf $TESTDIR
 	zfs set volsize=$volsize $TESTPOOL/$TESTVOL
 }
 
@@ -70,7 +69,6 @@ log_must zfs set volsize=128m $TESTPOOL/$TESTVOL
 echo "y" | newfs -v ${ZVOL_RDEVDIR}/$TESTPOOL/$TESTVOL >/dev/null 2>&1
 (( $? != 0 )) && log_fail "Unable to newfs(1M) $TESTPOOL/$TESTVOL"
 
-log_must mkdir $TESTDIR
 log_must mount ${ZVOL_DEVDIR}/$TESTPOOL/$TESTVOL $TESTDIR
 
 typeset -i fn=0

tests/zfs-tests/tests/functional/zvol/zvol_misc/zvol_misc_rename_inuse.ksh

@@ -0,0 +1,71 @@
+#!/bin/ksh -p
+#
+# This file and its contents are supplied under the terms of the
+# Common Development and Distribution License ("CDDL"), version 1.0.
+# You may only use this file in accordance with the terms of version
+# 1.0 of the CDDL.
+#
+# A full copy of the text of the CDDL should have accompanied this
+# source.  A copy of the CDDL is also available via the Internet at
+# http://www.illumos.org/license/CDDL.
+#
+
+#
+# Copyright 2019, loli10K <[email protected]>. All rights reserved.
+#
+
+. $STF_SUITE/include/libtest.shlib
+. $STF_SUITE/tests/functional/zvol/zvol_common.shlib
+. $STF_SUITE/tests/functional/zvol/zvol_misc/zvol_misc_common.kshlib
+
+#
+# DESCRIPTION:
+# Verify 'zfs rename' works on a ZVOL already in use as block device
+#
+# STRATEGY:
+# 1. Create a ZVOL
+# 2. Create a filesystem on the ZVOL device and mount it
+# 3. Rename the ZVOL dataset
+# 4. Receive a send stream with the same name as the old ZVOL dataset and verify
+#    we don't trigger any issue like the one reported in #6263
+#
+
+verify_runnable "global"
+
+function cleanup
+{
+	log_must umount "$MNTPFS"
+	log_must rmdir "$MNTPFS"
+	for ds in "$SENDFS" "$ZVOL" "$ZVOL-renamed"; do
+		destroy_dataset "$ds" '-rf'
+	done
+	udev_wait
+}
+
+log_assert "Verify 'zfs rename' works on a ZVOL already in use as block device"
+log_onexit cleanup
+
+ZVOL="$TESTPOOL/vol.$$"
+ZDEV="$ZVOL_DEVDIR/$ZVOL"
+MNTPFS="$TESTDIR/zvol_inuse_rename"
+SENDFS="$TESTPOOL/sendfs.$$"
+
+# 1. Create a ZVOL
+log_must zfs create -V $VOLSIZE "$ZVOL"
+
+# 2. Create a filesystem on the ZVOL device and mount it
+udev_wait
+log_must eval "echo y | newfs $ZDEV >/dev/null 2>&1"
+log_must mkdir "$MNTPFS"
+log_must mount "$ZDEV" "$MNTPFS"
+
+# 3. Rename the ZVOL dataset
+log_must zfs rename "$ZVOL" "$ZVOL-renamed"
+
+# 4. Receive a send stream with the same name as the old ZVOL dataset and verify
+#    we don't trigger any issue like the one reported in #6263
+log_must zfs create "$SENDFS"
+log_must zfs snap "$SENDFS@snap"
+log_must eval "zfs send $SENDFS@snap | zfs recv $ZVOL"
+
+log_pass "Renaming in use ZVOL works successfully"