Patch "xen/blkback: don't use xen_blkif_get() in xen-blkback kthread" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    xen/blkback: don't use xen_blkif_get() in xen-blkback kthread

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     xen-blkback-don-t-use-xen_blkif_get-in-xen-blkback-kthread.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From a24fa22ce22ae302b3bf8f7008896d52d5d57b8d Mon Sep 17 00:00:00 2001
From: Juergen Gross <jgross@suse.com>
Date: Thu, 18 May 2017 17:28:49 +0200
Subject: xen/blkback: don't use xen_blkif_get() in xen-blkback kthread
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

From: Juergen Gross <jgross@suse.com>

commit a24fa22ce22ae302b3bf8f7008896d52d5d57b8d upstream.

There is no need to use xen_blkif_get()/xen_blkif_put() in the kthread
of xen-blkback. Thread stopping is synchronous and using the blkif
reference counting in the kthread will avoid to ever let the reference
count drop to zero at the end of an I/O running concurrent to
disconnecting and multiple rings.

Setting ring->xenblkd to NULL after stopping the kthread isn't needed
as the kthread does this already.

Signed-off-by: Juergen Gross <jgross@suse.com>
Tested-by: Steven Haigh <netwiz@crc.id.au>
Acked-by: Roger Pau Monné <roger.pau@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/block/xen-blkback/blkback.c |    3 ---
 drivers/block/xen-blkback/xenbus.c  |    1 -
 2 files changed, 4 deletions(-)

--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -595,8 +595,6 @@ int xen_blkif_schedule(void *arg)
 	unsigned long timeout;
 	int ret;
 
-	xen_blkif_get(blkif);
-
 	while (!kthread_should_stop()) {
 		if (try_to_freeze())
 			continue;
@@ -650,7 +648,6 @@ purge_gnt_list:
 		print_stats(blkif);
 
 	blkif->xenblkd = NULL;
-	xen_blkif_put(blkif);
 
 	return 0;
 }
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -221,7 +221,6 @@ static int xen_blkif_disconnect(struct x
 	if (blkif->xenblkd) {
 		kthread_stop(blkif->xenblkd);
 		wake_up(&blkif->shutdown_wq);
-		blkif->xenblkd = NULL;
 	}
 
 	/* The above kthread_stop() guarantees that at this point we


Patches currently in stable-queue which might be from jgross@suse.com are

queue-4.4/xen-blkback-don-t-free-be-structure-too-early.patch
queue-4.4/xen-blkback-don-t-use-xen_blkif_get-in-xen-blkback-kthread.patch