[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>

5 files changed, 81 insertions, 0 deletions

diff --git a/fs/dlm/dlm_internal.h b/fs/dlm/dlm_internal.h
index a7435a8df35e..a006fa59e7da 100644
--- a/fs/dlm/dlm_internal.h
+++ b/fs/dlm/dlm_internal.h
@@ -216,6 +216,7 @@ struct dlm_args {
 #define DLM_IFL_ENDOFLIFE       0x00200000
 #define DLM_IFL_WATCH_TIMEWARN  0x00400000
 #define DLM_IFL_TIMEOUT_CANCEL  0x00800000
+#define DLM_IFL_DEADLOCK_CANCEL 0x01000000
 #define DLM_IFL_USER            0x00000001
 #define DLM_IFL_ORPHAN          0x00000002
 
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 */
 
diff --git a/fs/dlm/lock.h b/fs/dlm/lock.h
index 99ab4635074e..1720313c22df 100644
--- a/fs/dlm/lock.h
+++ b/fs/dlm/lock.h
@@ -49,6 +49,7 @@ int dlm_user_cancel(struct dlm_ls *ls,  struct dlm_user_args *ua_tmp,
         uint32_t flags, uint32_t lkid);
 int dlm_user_purge(struct dlm_ls *ls, struct dlm_user_proc *proc,
         int nodeid, int pid);
+int dlm_user_deadlock(struct dlm_ls *ls, uint32_t flags, uint32_t lkid);
 void dlm_clear_proc_locks(struct dlm_ls *ls, struct dlm_user_proc *proc);
 
 static inline int is_master(struct dlm_rsb *r)
diff --git a/fs/dlm/user.c b/fs/dlm/user.c
index 329da1b5285f..6438941ab1f8 100644
--- a/fs/dlm/user.c
+++ b/fs/dlm/user.c
@@ -156,6 +156,7 @@ static int lkb_is_endoflife(struct dlm_lkb *lkb, int sb_status, int type)
                 return 1;
         case -DLM_ECANCEL:
         case -ETIMEDOUT:
+        case -EDEADLK:
                 if (lkb->lkb_grmode == DLM_LOCK_IV)
                         return 1;
                 break;
@@ -320,6 +321,22 @@ static int device_user_unlock(struct dlm_user_proc *proc,
         return error;
 }
 
+static int device_user_deadlock(struct dlm_user_proc *proc,
+                                struct dlm_lock_params *params)
+{
+        struct dlm_ls *ls;
+        int error;
+
+        ls = dlm_find_lockspace_local(proc->lockspace);
+        if (!ls)
+                return -ENOENT;
+
+        error = dlm_user_deadlock(ls, params->flags, params->lkid);
+
+        dlm_put_lockspace(ls);
+        return error;
+}
+
 static int create_misc_device(struct dlm_ls *ls, char *name)
 {
         int error, len;
@@ -545,6 +562,14 @@ static ssize_t device_write(struct file *file, const char __user *buf,
                 error = device_user_unlock(proc, &kbuf->i.lock);
                 break;
 
+        case DLM_USER_DEADLOCK:
+                if (!proc) {
+                        log_print("no locking on control device");
+                        goto out_sig;
+                }
+                error = device_user_deadlock(proc, &kbuf->i.lock);
+                break;
+
         case DLM_USER_CREATE_LOCKSPACE:
                 if (proc) {
                         log_print("create/remove only on control device");
diff --git a/include/linux/dlm_device.h b/include/linux/dlm_device.h
index f7b9b57348a8..9642277a152a 100644
--- a/include/linux/dlm_device.h
+++ b/include/linux/dlm_device.h
@@ -92,6 +92,7 @@ struct dlm_lock_result {
 #define DLM_USER_CREATE_LOCKSPACE  4
 #define DLM_USER_REMOVE_LOCKSPACE  5
 #define DLM_USER_PURGE        6
+#define DLM_USER_DEADLOCK     7
 
 /* Arbitrary length restriction */
 #define MAX_LS_NAME_LEN 64