This patch implements dlm plock F_SETLKW interruption feature. If the
pending plock operation is not sent to user space yet it can simple be
dropped out of the send_list. In case it's already being sent we need to
try to remove the waiters in dlm user space tool. If it was successful a
reply with DLM_PLOCK_OP_CANCEL optype instead of DLM_PLOCK_OP_LOCK comes
back (flag DLM_PLOCK_FL_NO_REPLY was then being cleared in user space)
to signal the cancellation was successful. If a result with optype
DLM_PLOCK_OP_LOCK came back then the cancellation was not successful.
Signed-off-by: Alexander Aring <aahringo@xxxxxxxxxx>
---
fs/dlm/plock.c | 91 ++++++++++++++++++++++++----------
include/uapi/linux/dlm_plock.h | 1 +
2 files changed, 66 insertions(+), 26 deletions(-)
diff --git a/fs/dlm/plock.c b/fs/dlm/plock.c
index 1fa5b04d0298..0781a80c25f7 100644
--- a/fs/dlm/plock.c
+++ b/fs/dlm/plock.c
@@ -29,6 +29,9 @@ struct plock_async_data {
struct plock_op {
struct list_head list;
+#define DLM_PLOCK_OP_FLAG_SENT 0
+#define DLM_PLOCK_OP_FLAG_INTERRUPTED 1
+ unsigned long flags;
int done;
struct dlm_plock_info info;
/* if set indicates async handling */
@@ -74,30 +77,25 @@ static void send_op(struct plock_op *op)
wake_up(&send_wq);
}
-/* If a process was killed while waiting for the only plock on a file,
- locks_remove_posix will not see any lock on the file so it won't
- send an unlock-close to us to pass on to userspace to clean up the
- abandoned waiter. So, we have to insert the unlock-close when the
- lock call is interrupted. */
-
-static void do_unlock_close(const struct dlm_plock_info *info)
+static int do_lock_cancel(const struct plock_op *orig_op)
{
struct plock_op *op;
op = kzalloc(sizeof(*op), GFP_NOFS);
if (!op)
- return;
+ return -ENOMEM;
+
+ op->info = orig_op->info;
+ op->info.optype = DLM_PLOCK_OP_CANCEL;
+ op->info.flags = DLM_PLOCK_FL_NO_REPLY;
- op->info.optype = DLM_PLOCK_OP_UNLOCK;
- op->info.pid = info->pid;
- op->info.fsid = info->fsid;
- op->info.number = info->number;
- op->info.start = 0;
- op->info.end = OFFSET_MAX;
- op->info.owner = info->owner;
-
- op->info.flags |= (DLM_PLOCK_FL_CLOSE | DLM_PLOCK_FL_NO_REPLY);
send_op(op);
+ wait_event(recv_wq, (orig_op->done != 0));
+
+ if (orig_op->info.optype == DLM_PLOCK_OP_CANCEL)
+ return 0;
+
+ return 1;
}
int dlm_posix_lock(dlm_lockspace_t *lockspace, u64 number, struct file *file,
@@ -156,7 +154,7 @@ int dlm_posix_lock(dlm_lockspace_t *lockspace, u64 number, struct file *file,
send_op(op);
if (op->info.wait) {
- rv = wait_event_killable(recv_wq, (op->done != 0));
+ rv = wait_event_interruptible(recv_wq, (op->done != 0));
if (rv == -ERESTARTSYS) {
spin_lock(&ops_lock);
/* recheck under ops_lock if we got a done != 0,
@@ -166,17 +164,37 @@ int dlm_posix_lock(dlm_lockspace_t *lockspace, u64 number, struct file *file,
spin_unlock(&ops_lock);
goto do_lock_wait;
}
- list_del(&op->list);
- spin_unlock(&ops_lock);
+
+ if (!test_bit(DLM_PLOCK_OP_FLAG_SENT, &op->flags)) {
+ /* part of send_list, user never saw the op */
+ list_del(&op->list);
+ spin_unlock(&ops_lock);
+ rv = -EINTR;
+ } else {
+ set_bit(DLM_PLOCK_OP_FLAG_INTERRUPTED, &op->flags);
+ spin_unlock(&ops_lock);
+ rv = do_lock_cancel(op);
+ switch (rv) {
+ case 0:
+ rv = -EINTR;
+ break;
+ case 1:
+ /* cancellation wasn't successful but op is done */
+ goto do_lock_wait;
+ default:
+ /* internal error doing cancel we need to wait */
+ goto wait;
+ }
+ }
log_debug(ls, "%s: wait interrupted %x %llx pid %d",
__func__, ls->ls_global_id,
(unsigned long long)number, op->info.pid);
- do_unlock_close(&op->info);
dlm_release_plock_op(op);
goto out;
}
} else {
+wait:
wait_event(recv_wq, (op->done != 0));
}
@@ -392,10 +410,12 @@ static ssize_t dev_read(struct file *file, char __user *u, size_t count,
spin_lock(&ops_lock);
if (!list_empty(&send_list)) {
op = list_first_entry(&send_list, struct plock_op, list);
- if (op->info.flags & DLM_PLOCK_FL_NO_REPLY)
+ if (op->info.flags & DLM_PLOCK_FL_NO_REPLY) {
list_del(&op->list);
- else
+ } else {
list_move_tail(&op->list, &recv_list);
+ set_bit(DLM_PLOCK_OP_FLAG_SENT, &op->flags);
+ }
memcpy(&info, &op->info, sizeof(info));
}
spin_unlock(&ops_lock);
@@ -454,6 +474,27 @@ static ssize_t dev_write(struct file *file, const char __user *u, size_t count,
spin_lock(&ops_lock);
if (info.wait) {
list_for_each_entry(iter, &recv_list, list) {
+ /* A very specific posix lock case allows two
+ * lock request with the same meaning by using
+ * threads. It makes no sense from the application
+ * to do such request, however it is possible.
+ * We need to check the state for cancellation because
+ * we need to know the instance which is interrupted
+ * if two or more of the "same" lock requests are
+ * in waiting state and got interrupted.
+ *
+ * TODO we should move to a instance reference from
+ * request and reply and not go over lock states, but
+ * it seems going over lock states and get the instance
+ * does not make any problems (at least there were no
+ * issues found yet) but it's much cleaner to not think
+ * about all possible special cases and states to instance
+ * has no 1:1 mapping anymore.
+ */
+ if (info.optype == DLM_PLOCK_OP_CANCEL &&
+ !test_bit(DLM_PLOCK_OP_FLAG_INTERRUPTED, &iter->flags))
+ continue;
+
if (iter->info.fsid == info.fsid &&
iter->info.number == info.number &&
iter->info.owner == info.owner &&
@@ -477,9 +518,7 @@ static ssize_t dev_write(struct file *file, const char __user *u, size_t count,
if (op) {
/* Sanity check that op and info match. */
- if (info.wait)
- WARN_ON(op->info.optype != DLM_PLOCK_OP_LOCK);
- else
+ if (!info.wait)
WARN_ON(op->info.fsid != info.fsid ||
op->info.number != info.number ||
op->info.owner != info.owner ||
diff --git a/include/uapi/linux/dlm_plock.h b/include/uapi/linux/dlm_plock.h
index 8dfa272c929a..9c4c083c824a 100644
--- a/include/uapi/linux/dlm_plock.h
+++ b/include/uapi/linux/dlm_plock.h
@@ -22,6 +22,7 @@ enum {
DLM_PLOCK_OP_LOCK = 1,
DLM_PLOCK_OP_UNLOCK,
DLM_PLOCK_OP_GET,
+ DLM_PLOCK_OP_CANCEL,
};
#define DLM_PLOCK_FL_CLOSE 1
--
2.31.1
