Author: avg
Date: Sat Sep 22 17:42:53 2012
New Revision: 240831
URL: http://svn.freebsd.org/changeset/base/240831
Log:
zfs: allow a zvol to be used as a pool vdev, again
Do this by checking if spa_namespace_lock is already held and not taking
it again in that case.
Add a comment explaining why that is done and why it is safe.
Reviewed by: pjd
MFC after: 24 days
Modified:
head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zvol.c
Modified: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zvol.c
==============================================================================
--- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zvol.c Sat Sep 22
17:41:56 2012 (r240830)
+++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zvol.c Sat Sep 22
17:42:53 2012 (r240831)
@@ -878,27 +878,36 @@ zvol_open(struct g_provider *pp, int fla
{
zvol_state_t *zv;
int err = 0;
+ boolean_t locked = B_FALSE;
- if (MUTEX_HELD(&spa_namespace_lock)) {
- /*
- * If the spa_namespace_lock is being held, it means that ZFS
- * is trying to open ZVOL as its VDEV. This is not supported.
- */
- return (EOPNOTSUPP);
+ /*
+ * Protect against recursively entering spa_namespace_lock
+ * when spa_open() is used for a pool on a (local) ZVOL(s).
+ * This is needed since we replaced upstream zfsdev_state_lock
+ * with spa_namespace_lock in the ZVOL code.
+ * We are using the same trick as spa_open().
+ * Note that calls in zvol_first_open which need to resolve
+ * pool name to a spa object will enter spa_open()
+ * recursively, but that function already has all the
+ * necessary protection.
+ */
+ if (!MUTEX_HELD(&spa_namespace_lock)) {
+ mutex_enter(&spa_namespace_lock);
+ locked = B_TRUE;
}
- mutex_enter(&spa_namespace_lock);
-
zv = pp->private;
if (zv == NULL) {
- mutex_exit(&spa_namespace_lock);
+ if (locked)
+ mutex_exit(&spa_namespace_lock);
return (ENXIO);
}
if (zv->zv_total_opens == 0)
err = zvol_first_open(zv);
if (err) {
- mutex_exit(&spa_namespace_lock);
+ if (locked)
+ mutex_exit(&spa_namespace_lock);
return (err);
}
if ((flag & FWRITE) && (zv->zv_flags & ZVOL_RDONLY)) {
@@ -920,13 +929,15 @@ zvol_open(struct g_provider *pp, int fla
#endif
zv->zv_total_opens += count;
- mutex_exit(&spa_namespace_lock);
+ if (locked)
+ mutex_exit(&spa_namespace_lock);
return (err);
out:
if (zv->zv_total_opens == 0)
zvol_last_close(zv);
- mutex_exit(&spa_namespace_lock);
+ if (locked)
+ mutex_exit(&spa_namespace_lock);
return (err);
}
@@ -936,12 +947,18 @@ zvol_close(struct g_provider *pp, int fl
{
zvol_state_t *zv;
int error = 0;
+ boolean_t locked = B_FALSE;
- mutex_enter(&spa_namespace_lock);
+ /* See comment in zvol_open(). */
+ if (!MUTEX_HELD(&spa_namespace_lock)) {
+ mutex_enter(&spa_namespace_lock);
+ locked = B_TRUE;
+ }
zv = pp->private;
if (zv == NULL) {
- mutex_exit(&spa_namespace_lock);
+ if (locked)
+ mutex_exit(&spa_namespace_lock);
return (ENXIO);
}
@@ -964,7 +981,8 @@ zvol_close(struct g_provider *pp, int fl
if (zv->zv_total_opens == 0)
zvol_last_close(zv);
- mutex_exit(&spa_namespace_lock);
+ if (locked)
+ mutex_exit(&spa_namespace_lock);
return (error);
}
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