From: Xiubo Li <xiubli@redhat.com>
Date: Fri, 19 Feb 2021 14:05:23 +0000 (+0800)
Subject: client: wake up the front pos waiter
X-Git-Tag: v15.2.13~8^2~10^2
X-Git-Url: http://git.apps.os.sepia.ceph.com/?a=commitdiff_plain;h=b8aebba5979d15a8b9a262fe5a698fc6ea3cbae7;p=ceph.git

client: wake up the front pos waiter

The old code was buggy, why it ran well without any problem is that
the big client_lock will make sure that the read/write won't run in
parallel, so it won't be any problem here.

But when introducing inode lock to break the client_lock, which will
allow the read/write to run parallelly, the pos waiters won't get any
chance to be woke up.

In unlock_fh_pos(), it will always wake up the frontest waiter.

Fixes: https://tracker.ceph.com/issues/49379
Signed-off-by: Xiubo Li <xiubli@redhat.com>
(cherry picked from commit 66bcb880abe56c08e04876e98d3d751e78f8fd2f)
---

diff --git a/src/client/Client.cc b/src/client/Client.cc
index 06254493ea502..837860d1f43c4 100755
--- a/src/client/Client.cc
+++ b/src/client/Client.cc
@@ -9143,8 +9143,15 @@ void Client::lock_fh_pos(Fh *f)
 
 void Client::unlock_fh_pos(Fh *f)
 {
+  ceph_assert(ceph_mutex_is_locked_by_me(client_lock));
+
   ldout(cct, 10) << __func__ << " " << f << dendl;
   f->pos_locked = false;
+  if (!f->pos_waiters.empty()) {
+    // only wake up the oldest waiter
+    auto cond = f->pos_waiters.front();
+    cond->notify_one();
+  }
 }
 
 int Client::uninline_data(Inode *in, Context *onfinish)