Author: avg
Date: Fri Aug 21 08:17:44 2015
New Revision: 286985
URL: https://svnweb.freebsd.org/changeset/base/286985
Log:
try to fix lor between z_teardown_lock and spa_namespace_lock
The lock order reversal and a resulting deadlock were introduced
in r285021 / D2865. The problem is that zfs_register_callbacks() calls
dsl_prop_get_integer() that has to acquire spa_namespace_lock.
At the same time, spa_config_sync() is called with spa_namespace_lock
held and then it performs ZFS vnode operations that acquire
z_teardown_lock in the reader mode.
So, fix the problem by using dsl_prop_get_int_ds() instead of
dsl_prop_get_integer(). The former does not need to look up
the pool and the dataset by name.
Reported by: many
Reviewed by: delphij
Tested by: delphij, Jens Schweikhardt <schwe...@schweikhardt.net>
MFC after: 5 days
X-MFC with: r285021
Modified:
head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vfsops.c
Modified: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vfsops.c
==============================================================================
--- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vfsops.c Fri Aug
21 08:06:18 2015 (r286984)
+++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vfsops.c Fri Aug
21 08:17:44 2015 (r286985)
@@ -472,6 +472,19 @@ zfs_register_callbacks(vfs_t *vfsp)
}
/*
+ * We need to enter pool configuration here, so that we can use
+ * dsl_prop_get_int_ds() to handle the special nbmand property below.
+ * dsl_prop_get_integer() can not be used, because it has to acquire
+ * spa_namespace_lock and we can not do that because we already hold
+ * z_teardown_lock. The problem is that spa_config_sync() is called
+ * with spa_namespace_lock held and the function calls ZFS vnode
+ * operations to write the cache file and thus z_teardown_lock is
+ * acquired after spa_namespace_lock.
+ */
+ ds = dmu_objset_ds(os);
+ dsl_pool_config_enter(dmu_objset_pool(os), FTAG);
+
+ /*
* nbmand is a special property. It can only be changed at
* mount time.
*
@@ -482,14 +495,9 @@ zfs_register_callbacks(vfs_t *vfsp)
nbmand = B_FALSE;
} else if (vfs_optionisset(vfsp, MNTOPT_NBMAND, NULL)) {
nbmand = B_TRUE;
- } else {
- char osname[MAXNAMELEN];
-
- dmu_objset_name(os, osname);
- if (error = dsl_prop_get_integer(osname, "nbmand", &nbmand,
- NULL)) {
- return (error);
- }
+ } else if (error = dsl_prop_get_int_ds(ds, "nbmand", &nbmand) != 0) {
+ dsl_pool_config_exit(dmu_objset_pool(os), FTAG);
+ return (error);
}
/*
@@ -499,8 +507,6 @@ zfs_register_callbacks(vfs_t *vfsp)
* the first prop_register(), but I guess I like to go
* overboard...
*/
- ds = dmu_objset_ds(os);
- dsl_pool_config_enter(dmu_objset_pool(os), FTAG);
error = dsl_prop_register(ds,
zfs_prop_to_name(ZFS_PROP_ATIME), atime_changed_cb, zfsvfs);
error = error ? error : dsl_prop_register(ds,
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