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FreeBSD: Avoid spurious EINTR in zvol_cdev_open

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zvol_first_open can fail with EINTR if spa_namespace_lock is not held
and cannot be taken without waiting.

Apply the same logic that was done for zvol_geom_open to take
spa_namespace_lock if not already held on first open in zvol_cdev_open.

Reviewed-by: Matt Macy <mmacy@FreeBSD.org>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Signed-off-by: Ryan Moeller <ryan@iXsystems.com>
Closes #11175
This commit is contained in:
Ryan Moeller 2020-11-06 13:52:16 -05:00 committed by Brian Behlendorf
parent d1dd72a2c5
commit 2186ed33f1
1 changed files with 20 additions and 1 deletions
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21
module/os/freebsd/zfs/zvol_os.c
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@ -827,14 +827,30 @@ zvol_cdev_open(struct cdev *dev, int flags, int fmt, struct thread *td)
struct zvol_state_dev *zsd;
int err = 0;
boolean_t drop_suspend = B_TRUE;
boolean_t drop_namespace = B_FALSE;
retry:
rw_enter(&zvol_state_lock, ZVOL_RW_READER);
zv = dev->si_drv2;
if (zv == NULL) {
if (drop_namespace)
mutex_exit(&spa_namespace_lock);
rw_exit(&zvol_state_lock);
return (SET_ERROR(ENXIO));
}
if (zv->zv_open_count == 0 && !mutex_owned(&spa_namespace_lock)) {
/*
* We need to guarantee that the namespace lock is held
* to avoid spurious failures in zvol_first_open
*/
drop_namespace = B_TRUE;
if (!mutex_tryenter(&spa_namespace_lock)) {
rw_exit(&zvol_state_lock);
mutex_enter(&spa_namespace_lock);
goto retry;
}
}
mutex_enter(&zv->zv_state_lock);
ASSERT3S(zv->zv_zso->zso_volmode, ==, ZFS_VOLMODE_DEV);
@ -895,7 +911,8 @@ zvol_cdev_open(struct cdev *dev, int flags, int fmt, struct thread *td)
(zv->zv_flags & ZVOL_WRITTEN_TO) != 0)
zil_async_to_sync(zv->zv_zilog, ZVOL_OBJ);
}
if (drop_namespace)
mutex_exit(&spa_namespace_lock);
mutex_exit(&zv->zv_state_lock);
if (drop_suspend)
rw_exit(&zv->zv_suspend_lock);
@ -905,6 +922,8 @@ zvol_cdev_open(struct cdev *dev, int flags, int fmt, struct thread *td)
if (zv->zv_open_count == 0)
zvol_last_close(zv);
out_locked:
if (drop_namespace)
mutex_exit(&spa_namespace_lock);
mutex_exit(&zv->zv_state_lock);
if (drop_suspend)
rw_exit(&zv->zv_suspend_lock);