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Fix zpool on zvol deadlock

Commit 65d5608 fixes the lock
inversion between spa_namespace_lock and bdev->bd_mutex but only
for the first user of spa_namespace_lock: dmu_objset_own().
Later spa_namespace_lock gets acquired by dsl_prop_get_integer()
though dsl_prop_get()->dsl_dataset_hold()->dsl_dir_open_spa()->
spa_open()->spa_open_common() without this "protection".  By
moving the mutex release after this second use, even this
acquisition of the lock is "protected" by the ERESTARTSYS trick.

Signed-off-by: Massimo Maggi <me@massimo-maggi.eu>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1220
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maxximino authored and behlendorf committed Jan 18, 2013
1 parent 7973e46 commit babf3f9b6d9294b0a88457941d60af5d9d7b744d
Showing with 13 additions and 13 deletions.
  1. +13 −13 module/zfs/zvol.c
@@ -920,24 +920,20 @@ zvol_first_open(zvol_state_t *zv)

/* lie and say we're read-only */
error = dmu_objset_own(zv->zv_name, DMU_OST_ZVOL, 1, zvol_tag, &os);

if (locked)
mutex_exit(&spa_namespace_lock);

if (error)
return (-error);
goto out_mutex;

error = zap_lookup(os, ZVOL_ZAP_OBJ, "size", 8, 1, &volsize);
if (error) {
dmu_objset_disown(os, zvol_tag);
return (-error);
dmu_objset_disown(os, zvol_tag);
goto out_mutex;
}

zv->zv_objset = os;
error = dmu_bonus_hold(os, ZVOL_OBJ, zvol_tag, &zv->zv_dbuf);
if (error) {
dmu_objset_disown(os, zvol_tag);
return (-error);
dmu_objset_disown(os, zvol_tag);
goto out_mutex;
}

set_capacity(zv->zv_disk, volsize >> 9);
@@ -946,13 +942,17 @@ zvol_first_open(zvol_state_t *zv)

VERIFY(dsl_prop_get_integer(zv->zv_name, "readonly", &ro, NULL) == 0);
if (ro || dmu_objset_is_snapshot(os)) {
set_disk_ro(zv->zv_disk, 1);
zv->zv_flags |= ZVOL_RDONLY;
set_disk_ro(zv->zv_disk, 1);
zv->zv_flags |= ZVOL_RDONLY;
} else {
set_disk_ro(zv->zv_disk, 0);
zv->zv_flags &= ~ZVOL_RDONLY;
set_disk_ro(zv->zv_disk, 0);
zv->zv_flags &= ~ZVOL_RDONLY;
}

out_mutex:
if (locked)
mutex_exit(&spa_namespace_lock);

return (-error);
}

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