[DLM] canceling deadlocked lock

Add a function that can be used through libdlm by a system daemon to cancel
another process's deadlocked lock.  A completion ast with EDEADLK is returned
to the process waiting for the lock.

Signed-off-by: David Teigland <teigland@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

1 files changed, 53 insertions, 0 deletions

diff --git a/fs/dlm/lock.c b/fs/dlm/lock.c
index df91578145d1..de943afacb37 100644
--- a/fs/dlm/lock.c
+++ b/fs/dlm/lock.c
@@ -300,6 +300,11 @@ static void queue_cast(struct dlm_rsb *r, struct dlm_lkb *lkb, int rv)
                 rv = -ETIMEDOUT;
         }
 
+        if (rv == -DLM_ECANCEL && (lkb->lkb_flags & DLM_IFL_DEADLOCK_CANCEL)) {
+                lkb->lkb_flags &= ~DLM_IFL_DEADLOCK_CANCEL;
+                rv = -EDEADLK;
+        }
+
         lkb->lkb_lksb->sb_status = rv;
         lkb->lkb_lksb->sb_flags = lkb->lkb_sbflags;
 
@@ -4450,6 +4455,54 @@ int dlm_user_cancel(struct dlm_ls *ls, struct dlm_user_args *ua_tmp,
         return error;
 }
 
+int dlm_user_deadlock(struct dlm_ls *ls, uint32_t flags, uint32_t lkid)
+{
+        struct dlm_lkb *lkb;
+        struct dlm_args args;
+        struct dlm_user_args *ua;
+        struct dlm_rsb *r;
+        int error;
+
+        dlm_lock_recovery(ls);
+
+        error = find_lkb(ls, lkid, &lkb);
+        if (error)
+                goto out;
+
+        ua = (struct dlm_user_args *)lkb->lkb_astparam;
+
+        error = set_unlock_args(flags, ua, &args);
+        if (error)
+                goto out_put;
+
+        /* same as cancel_lock(), but set DEADLOCK_CANCEL after lock_rsb */
+
+        r = lkb->lkb_resource;
+        hold_rsb(r);
+        lock_rsb(r);
+
+        error = validate_unlock_args(lkb, &args);
+        if (error)
+                goto out_r;
+        lkb->lkb_flags |= DLM_IFL_DEADLOCK_CANCEL;
+
+        error = _cancel_lock(r, lkb);
+ out_r:
+        unlock_rsb(r);
+        put_rsb(r);
+
+        if (error == -DLM_ECANCEL)
+                error = 0;
+        /* from validate_unlock_args() */
+        if (error == -EBUSY)
+                error = 0;
+ out_put:
+        dlm_put_lkb(lkb);
+ out:
+        dlm_unlock_recovery(ls);
+        return error;
+}
+
 /* lkb's that are removed from the waiters list by revert are just left on the
    orphans list with the granted orphan locks, to be freed by purge */