[lustre-devel] [PATCH 05/28] lustre: obd_type: discard obd_type_lock
James Simmons
jsimmons at infradead.org
Thu Mar 21 20:53:03 PDT 2019
> This lock is only used to protect typ_refcnt, so change
> that to an atomic_t and discard the lock.
>
> The lock also covers calls to try_module_get and module_put,
> but this serves no purpose as it does not prevent the module
> from being unloaded.
>
> Finally, the return value for the call to try_module_get is
> ignored, which is not safe.
Nak. Looking at the code we can easily use the kref of the
kobject instead. The two special cases for the ref_count
can be removed. The one for mdc_request was removed in
patch https://review.whamcloud.com/30419. The other refcount
use in mgc looks like its for supporting lustre 1.4 version
logs. I bet that can be removed. Andreas can state if it
is still need.
> Signed-off-by: NeilBrown <neilb at suse.com>
> ---
> drivers/staging/lustre/lustre/include/obd.h | 3 +-
> drivers/staging/lustre/lustre/mdc/mdc_request.c | 2 +
> drivers/staging/lustre/lustre/mgc/mgc_request.c | 2 +
> drivers/staging/lustre/lustre/obdclass/genops.c | 30 +++++++++-----------
> drivers/staging/lustre/lustre/obdclass/lu_object.c | 2 +
> 5 files changed, 18 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/staging/lustre/lustre/include/obd.h b/drivers/staging/lustre/lustre/include/obd.h
> index 4c58b916e0a3..61fb8159af20 100644
> --- a/drivers/staging/lustre/lustre/include/obd.h
> +++ b/drivers/staging/lustre/lustre/include/obd.h
> @@ -102,9 +102,8 @@ struct obd_type {
> struct obd_ops *typ_dt_ops;
> struct md_ops *typ_md_ops;
> struct dentry *typ_debugfs_entry;
> - int typ_refcnt;
> + atomic_t typ_refcnt;
> struct lu_device_type *typ_lu;
> - spinlock_t obd_type_lock;
> struct kobject typ_kobj;
> };
> #define typ_name typ_kobj.name
> diff --git a/drivers/staging/lustre/lustre/mdc/mdc_request.c b/drivers/staging/lustre/lustre/mdc/mdc_request.c
> index bc764f9dd102..705a4e3b518a 100644
> --- a/drivers/staging/lustre/lustre/mdc/mdc_request.c
> +++ b/drivers/staging/lustre/lustre/mdc/mdc_request.c
> @@ -2542,7 +2542,7 @@ static int mdc_init_ea_size(struct obd_export *exp, u32 easize, u32 def_easize)
> static int mdc_precleanup(struct obd_device *obd)
> {
> /* Failsafe, ok if racy */
> - if (obd->obd_type->typ_refcnt <= 1)
> + if (atomic_read(&obd->obd_type->typ_refcnt) <= 1)
> libcfs_kkuc_group_rem(0, KUC_GRP_HSM);
>
> mdc_changelog_cdev_finish(obd);
> diff --git a/drivers/staging/lustre/lustre/mgc/mgc_request.c b/drivers/staging/lustre/lustre/mgc/mgc_request.c
> index 84ba6d0e3493..0580afa2755d 100644
> --- a/drivers/staging/lustre/lustre/mgc/mgc_request.c
> +++ b/drivers/staging/lustre/lustre/mgc/mgc_request.c
> @@ -715,7 +715,7 @@ static int mgc_cleanup(struct obd_device *obd)
> /* COMPAT_146 - old config logs may have added profiles we don't
> * know about
> */
> - if (obd->obd_type->typ_refcnt <= 1)
> + if (atomic_read(&obd->obd_type->typ_refcnt) <= 1)
> /* Only for the last mgc */
> class_del_profiles();
>
> diff --git a/drivers/staging/lustre/lustre/obdclass/genops.c b/drivers/staging/lustre/lustre/obdclass/genops.c
> index 74195de639e4..02d829617519 100644
> --- a/drivers/staging/lustre/lustre/obdclass/genops.c
> +++ b/drivers/staging/lustre/lustre/obdclass/genops.c
> @@ -113,15 +113,17 @@ static struct obd_type *class_get_type(const char *name)
> }
> }
> if (type) {
> - spin_lock(&type->obd_type_lock);
> - type->typ_refcnt++;
> - try_module_get(type->typ_dt_ops->owner);
> - spin_unlock(&type->obd_type_lock);
> - /* class_search_type() returned a counted reference,
> - * but we don't need that count any more as
> - * we have one through typ_refcnt.
> - */
> - kobject_put(&type->typ_kobj);
> + if (try_module_get(type->typ_dt_ops->owner)) {
> + atomic_inc(&type->typ_refcnt);
> + /* class_search_type() returned a counted reference,
> + * but we don't need that count any more as
> + * we have one through typ_refcnt.
> + */
> + kobject_put(&type->typ_kobj);
> + } else {
> + kobject_put(&type->typ_kobj);
> + type = NULL;
> + }
> }
> return type;
> }
> @@ -129,10 +131,7 @@ static struct obd_type *class_get_type(const char *name)
> void class_put_type(struct obd_type *type)
> {
> LASSERT(type);
> - spin_lock(&type->obd_type_lock);
> - type->typ_refcnt--;
> - module_put(type->typ_dt_ops->owner);
> - spin_unlock(&type->obd_type_lock);
> + atomic_dec(&type->typ_refcnt);
> }
>
> static void simple_class_release(struct kobject *kobj)
> @@ -222,7 +221,6 @@ int class_register_type(struct obd_ops *dt_ops, struct md_ops *md_ops,
> /* md_ops is optional */
> if (md_ops)
> *type->typ_md_ops = *md_ops;
> - spin_lock_init(&type->obd_type_lock);
>
> rc = kobject_add(&type->typ_kobj, &lustre_kset->kobj, "%s", name);
> if (rc)
> @@ -256,8 +254,8 @@ int class_unregister_type(const char *name)
> return -EINVAL;
> }
>
> - if (type->typ_refcnt) {
> - CERROR("type %s has refcount (%d)\n", name, type->typ_refcnt);
> + if (atomic_read(&type->typ_refcnt)) {
> + CERROR("type %s has refcount (%d)\n", name, atomic_read(&type->typ_refcnt));
> /* This is a bad situation, let's make the best of it */
> /* Remove ops, but leave the name for debugging */
> kfree(type->typ_dt_ops);
> diff --git a/drivers/staging/lustre/lustre/obdclass/lu_object.c b/drivers/staging/lustre/lustre/obdclass/lu_object.c
> index 9c872db21040..770cc1b9e40b 100644
> --- a/drivers/staging/lustre/lustre/obdclass/lu_object.c
> +++ b/drivers/staging/lustre/lustre/obdclass/lu_object.c
> @@ -1267,7 +1267,7 @@ void lu_stack_fini(const struct lu_env *env, struct lu_device *top)
> next = ldt->ldt_ops->ldto_device_free(env, scan);
> type = ldt->ldt_obd_type;
> if (type) {
> - type->typ_refcnt--;
> + atomic_dec(&type->typ_refcnt);
> class_put_type(type);
> }
> }
>
>
>
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