[Cluster-devel] [PATCH dlm/next 2/3] fs: dlm: fix context imbalance warning in __put_lkb()

[Alexander Aring]

This patch fixes the following sparse warning:

warning: context imbalance in '__put_lkb' - unexpected unlock

it does this by unlock the ls_lkbidr_spin lock inside of the release
functionality of kref_put_lock() and do a __releases() annotation at the
release function. The kref_put_lock() for __put_lkb() has a special
requirement to pass an additional dlm_ls pointer to the release callback,
this is done by providing an own implementation of kref_put_lock() that
is named dlm_kref_put_lock() and can pass an additional parameter.

Signed-off-by: Alexander Aring <aahri...@redhat.com>
---
 fs/dlm/lock.c | 46 +++++++++++++++++++++++++++-------------------
 1 file changed, 27 insertions(+), 19 deletions(-)

diff --git a/fs/dlm/lock.c b/fs/dlm/lock.c
index dac7eb75dba9..4b5cff76d376 100644
--- a/fs/dlm/lock.c
+++ b/fs/dlm/lock.c
@@ -1256,7 +1256,8 @@ static int find_lkb(struct dlm_ls *ls, uint32_t lkid, 
struct dlm_lkb **lkb_ret)
        return lkb ? 0 : -ENOENT;
 }
 
-static void kill_lkb(struct kref *kref)
+static void kill_lkb(struct kref *kref, struct dlm_ls *ls)
+        __releases(&ls->ls_lkbidr_spin)
 {
        struct dlm_lkb *lkb = container_of(kref, struct dlm_lkb, lkb_ref);
 
@@ -1264,6 +1265,29 @@ static void kill_lkb(struct kref *kref)
           can release the write_lock before the detach_lkb */
 
        DLM_ASSERT(!lkb->lkb_status, dlm_print_lkb(lkb););
+
+       idr_remove(&ls->ls_lkbidr, lkb->lkb_id);
+       spin_unlock(&ls->ls_lkbidr_spin);
+
+       detach_lkb(lkb);
+
+       /* for local/process lkbs, lvbptr points to caller's lksb */
+       if (lkb->lkb_lvbptr && is_master_copy(lkb))
+               dlm_free_lvb(lkb->lkb_lvbptr);
+       dlm_free_lkb(lkb);
+}
+
+static inline int dlm_kref_put_lock(struct kref *kref,
+                                   void (*release)(struct kref *kref,
+                                                   struct dlm_ls *ls),
+                                   spinlock_t *lock,
+                                   struct dlm_ls *ls)
+{
+       if (refcount_dec_and_lock(&kref->refcount, lock)) {
+               release(kref, ls);
+               return 1;
+       }
+       return 0;
 }
 
 /* __put_lkb() is used when an lkb may not have an rsb attached to
@@ -1271,24 +1295,8 @@ static void kill_lkb(struct kref *kref)
 
 static int __put_lkb(struct dlm_ls *ls, struct dlm_lkb *lkb)
 {
-       uint32_t lkid = lkb->lkb_id;
-       int rv;
-
-       rv = kref_put_lock(&lkb->lkb_ref, kill_lkb,
-                          &ls->ls_lkbidr_spin);
-       if (rv) {
-               idr_remove(&ls->ls_lkbidr, lkid);
-               spin_unlock(&ls->ls_lkbidr_spin);
-
-               detach_lkb(lkb);
-
-               /* for local/process lkbs, lvbptr points to caller's lksb */
-               if (lkb->lkb_lvbptr && is_master_copy(lkb))
-                       dlm_free_lvb(lkb->lkb_lvbptr);
-               dlm_free_lkb(lkb);
-       }
-
-       return rv;
+       return dlm_kref_put_lock(&lkb->lkb_ref, kill_lkb,
+                                &ls->ls_lkbidr_spin, ls);
 }
 
 int dlm_put_lkb(struct dlm_lkb *lkb)
-- 
2.31.1