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FreeBSD: Simplify zvol_geom_open and zvol_cdev_open
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We can consolidate the unlocking procedure into one place by starting
with drop_suspend set to B_FALSE and moving the open count check up.

While here, a little code cleanup. Match the out labels between
zvol_geom_open and zvol_cdev_open, and add a missing period in some
comments.

Reviewed-by: Matt Macy <[email protected]>
Reviewed-by: Alexander Motin <[email protected]>
Signed-off-by: Ryan Moeller <[email protected]>
Closes #11175
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@behlendorf
Ryan Moeller authored and behlendorf committed Nov 11, 2020
1 parent 4a2e981 commit cb4d3fb
Showing 1 changed file with 16 additions and 36 deletions.
52 changes: 16 additions & 36 deletions module/os/freebsd/zfs/zvol_os.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -209,7 +209,7 @@ zvol_geom_open(struct g_provider *pp, int flag, int count)
{
zvol_state_t *zv;
int err = 0;
boolean_t drop_suspend = B_TRUE;
boolean_t drop_suspend = B_FALSE;
boolean_t drop_namespace = B_FALSE;

if (!zpool_on_zvol && tsd_get(zfs_geom_probe_vdev_key) != NULL) {
Expand All @@ -228,16 +228,14 @@ zvol_geom_open(struct g_provider *pp, int flag, int count)
rw_enter(&zvol_state_lock, ZVOL_RW_READER);
zv = pp->private;
if (zv == NULL) {
if (drop_namespace)
mutex_exit(&spa_namespace_lock);
rw_exit(&zvol_state_lock);
return (SET_ERROR(ENXIO));
err = SET_ERROR(ENXIO);
goto out_locked;
}

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
* to avoid spurious failures in zvol_first_open.
*/
drop_namespace = B_TRUE;
if (!mutex_tryenter(&spa_namespace_lock)) {
Expand All @@ -256,6 +254,7 @@ zvol_geom_open(struct g_provider *pp, int flag, int count)
* ordering - zv_suspend_lock before zv_state_lock
*/
if (zv->zv_open_count == 0) {
drop_suspend = B_TRUE;
if (!rw_tryenter(&zv->zv_suspend_lock, ZVOL_RW_READER)) {
mutex_exit(&zv->zv_state_lock);
rw_enter(&zv->zv_suspend_lock, ZVOL_RW_READER);
Expand All @@ -266,8 +265,6 @@ zvol_geom_open(struct g_provider *pp, int flag, int count)
drop_suspend = B_FALSE;
}
}
} else {
drop_suspend = B_FALSE;
}
rw_exit(&zvol_state_lock);

Expand All @@ -277,7 +274,7 @@ zvol_geom_open(struct g_provider *pp, int flag, int count)
ASSERT(ZVOL_RW_READ_HELD(&zv->zv_suspend_lock));
err = zvol_first_open(zv, !(flag & FWRITE));
if (err)
goto out_mutex;
goto out_locked;
pp->mediasize = zv->zv_volsize;
pp->stripeoffset = 0;
pp->stripesize = zv->zv_volblocksize;
Expand All @@ -290,34 +287,27 @@ zvol_geom_open(struct g_provider *pp, int flag, int count)
if ((flag & FWRITE) && ((zv->zv_flags & ZVOL_RDONLY) ||
dmu_objset_incompatible_encryption_version(zv->zv_objset))) {
err = SET_ERROR(EROFS);
goto out_open_count;
goto out_opened;
}
if (zv->zv_flags & ZVOL_EXCL) {
err = SET_ERROR(EBUSY);
goto out_open_count;
goto out_opened;
}
#ifdef FEXCL
if (flag & FEXCL) {
if (zv->zv_open_count != 0) {
err = SET_ERROR(EBUSY);
goto out_open_count;
goto out_opened;
}
zv->zv_flags |= ZVOL_EXCL;
}
#endif

zv->zv_open_count += count;
if (drop_namespace)
mutex_exit(&spa_namespace_lock);
mutex_exit(&zv->zv_state_lock);
if (drop_suspend)
rw_exit(&zv->zv_suspend_lock);
return (0);

out_open_count:
out_opened:
if (zv->zv_open_count == 0)
zvol_last_close(zv);
out_mutex:
out_locked:
if (drop_namespace)
mutex_exit(&spa_namespace_lock);
mutex_exit(&zv->zv_state_lock);
Expand Down Expand Up @@ -826,23 +816,21 @@ zvol_cdev_open(struct cdev *dev, int flags, int fmt, struct thread *td)
zvol_state_t *zv;
struct zvol_state_dev *zsd;
int err = 0;
boolean_t drop_suspend = B_TRUE;
boolean_t drop_suspend = B_FALSE;
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));
err = SET_ERROR(ENXIO);
goto out_locked;
}

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
* to avoid spurious failures in zvol_first_open.
*/
drop_namespace = B_TRUE;
if (!mutex_tryenter(&spa_namespace_lock)) {
Expand All @@ -861,6 +849,7 @@ zvol_cdev_open(struct cdev *dev, int flags, int fmt, struct thread *td)
* ordering - zv_suspend_lock before zv_state_lock
*/
if (zv->zv_open_count == 0) {
drop_suspend = B_TRUE;
if (!rw_tryenter(&zv->zv_suspend_lock, ZVOL_RW_READER)) {
mutex_exit(&zv->zv_state_lock);
rw_enter(&zv->zv_suspend_lock, ZVOL_RW_READER);
Expand All @@ -871,8 +860,6 @@ zvol_cdev_open(struct cdev *dev, int flags, int fmt, struct thread *td)
drop_suspend = B_FALSE;
}
}
} else {
drop_suspend = B_FALSE;
}
rw_exit(&zvol_state_lock);

Expand Down Expand Up @@ -911,13 +898,6 @@ 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);
return (0);

out_opened:
if (zv->zv_open_count == 0)
zvol_last_close(zv);
Expand Down

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