[Devel] [PATCH RHEL7 COMMIT] ms/nfsd: minor 4.1 callback cleanup

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-1062.12.1.vz7.131.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-1062.12.1.vz7.131.4
------>
commit 990cdda12fbfc3e0fbf3f8fa1c512f27b2e7fef9
Author: Trond Myklebust <trondmy at gmail.com>
Date:   Thu Feb 27 13:01:25 2020 +0300

    ms/nfsd: minor 4.1 callback cleanup
    
    Move all the cb_holds_slot management into helper functions.  No change
    in behavior.
    
    Signed-off-by: Trond Myklebust <trond.myklebust at hammerspace.com>
    Signed-off-by: J. Bruce Fields <bfields at redhat.com>
    (cherry picked from commit 12357f1b2c8e0d06f34a045498d4a1e7877153ee)
    Signed-off-by: Dave Wysochanski <dwysocha at redhat.com>
    
    Taken from https://bugzilla.redhat.com/show_bug.cgi?id=1448750
    https://jira.sw.ru/browse/PSBM-100902
    Signed-off-by: Vasily Averin <vvs at virtuozzo.com>
---
 fs/nfsd/nfs4callback.c | 30 ++++++++++++++++++++----------
 1 file changed, 20 insertions(+), 10 deletions(-)

diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
index c69400f08ed4d..d692b9756e847 100644
--- a/fs/nfsd/nfs4callback.c
+++ b/fs/nfsd/nfs4callback.c
@@ -898,9 +898,12 @@ void nfsd4_change_callback(struct nfs4_client *clp, struct nfs4_cb_conn *conn)
  * If the slot is available, then mark it busy.  Otherwise, set the
  * thread for sleeping on the callback RPC wait queue.
  */
-static bool nfsd41_cb_get_slot(struct nfs4_client *clp, struct rpc_task *task)
+static bool nfsd41_cb_get_slot(struct nfsd4_callback *cb, struct rpc_task *task)
 {
-	if (test_and_set_bit(0, &clp->cl_cb_slot_busy) != 0) {
+	struct nfs4_client *clp = cb->cb_clp;
+
+	if (!cb->cb_holds_slot &&
+	    test_and_set_bit(0, &clp->cl_cb_slot_busy) != 0) {
 		rpc_sleep_on(&clp->cl_cb_waitq, task, NULL);
 		/* Race breaker */
 		if (test_and_set_bit(0, &clp->cl_cb_slot_busy) != 0) {
@@ -909,9 +912,21 @@ static bool nfsd41_cb_get_slot(struct nfs4_client *clp, struct rpc_task *task)
 		}
 		rpc_wake_up_queued_task(&clp->cl_cb_waitq, task);
 	}
+	cb->cb_holds_slot = true;
 	return true;
 }
 
+static void nfsd41_cb_release_slot(struct nfsd4_callback *cb)
+{
+	struct nfs4_client *clp = cb->cb_clp;
+
+	if (cb->cb_holds_slot) {
+		cb->cb_holds_slot = false;
+		clear_bit(0, &clp->cl_cb_slot_busy);
+		rpc_wake_up_next(&clp->cl_cb_waitq);
+	}
+}
+
 /*
  * TODO: cb_sequence should support referring call lists, cachethis, multiple
  * slots, and mark callback channel down on communication errors.
@@ -929,11 +944,8 @@ static void nfsd4_cb_prepare(struct rpc_task *task, void *calldata)
 	 */
 	cb->cb_seq_status = 1;
 	cb->cb_status = 0;
-	if (minorversion) {
-		if (!cb->cb_holds_slot && !nfsd41_cb_get_slot(clp, task))
-			return;
-		cb->cb_holds_slot = true;
-	}
+	if (minorversion && !nfsd41_cb_get_slot(cb, task))
+		return;
 	rpc_call_start(task);
 }
 
@@ -999,9 +1011,7 @@ static bool nfsd4_cb_sequence_done(struct rpc_task *task, struct nfsd4_callback
 			cb->cb_seq_status);
 	}
 
-	cb->cb_holds_slot = false;
-	clear_bit(0, &clp->cl_cb_slot_busy);
-	rpc_wake_up_next(&clp->cl_cb_waitq);
+	nfsd41_cb_release_slot(cb);
 	dprintk("%s: freed slot, new seqid=%d\n", __func__,
 		clp->cl_cb_session->se_cb_seq_nr);