[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 <aahringo at 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