[PATCH 4.9 023/130] xen/scsiback: add error handling for xenbus_printf

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Zhouyang Jia <jiazhouyan...@gmail.com>

[ Upstream commit 7c63ca24c878e0051c91904b72174029320ef4bd ]

When xenbus_printf fails, the lack of error-handling code may
cause unexpected results.

This patch adds error-handling code after calling xenbus_printf.

Signed-off-by: Zhouyang Jia <jiazhouyan...@gmail.com>
Reviewed-by: Juergen Gross <jgr...@suse.com>
Signed-off-by: Juergen Gross <jgr...@suse.com>
Signed-off-by: Sasha Levin <alexander.le...@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 drivers/xen/xen-scsiback.c |   16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

--- a/drivers/xen/xen-scsiback.c
+++ b/drivers/xen/xen-scsiback.c
@@ -1014,6 +1014,7 @@ static void scsiback_do_add_lun(struct v
 {
        struct v2p_entry *entry;
        unsigned long flags;
+       int err;
 
        if (try) {
                spin_lock_irqsave(&info->v2p_lock, flags);
@@ -1029,8 +1030,11 @@ static void scsiback_do_add_lun(struct v
                        scsiback_del_translation_entry(info, vir);
                }
        } else if (!try) {
-               xenbus_printf(XBT_NIL, info->dev->nodename, state,
+               err = xenbus_printf(XBT_NIL, info->dev->nodename, state,
                              "%d", XenbusStateClosed);
+               if (err)
+                       xenbus_dev_error(info->dev, err,
+                               "%s: writing %s", __func__, state);
        }
 }
 
@@ -1069,8 +1073,11 @@ static void scsiback_do_1lun_hotplug(str
        snprintf(str, sizeof(str), "vscsi-devs/%s/p-dev", ent);
        val = xenbus_read(XBT_NIL, dev->nodename, str, NULL);
        if (IS_ERR(val)) {
-               xenbus_printf(XBT_NIL, dev->nodename, state,
+               err = xenbus_printf(XBT_NIL, dev->nodename, state,
                              "%d", XenbusStateClosed);
+               if (err)
+                       xenbus_dev_error(info->dev, err,
+                               "%s: writing %s", __func__, state);
                return;
        }
        strlcpy(phy, val, VSCSI_NAMELEN);
@@ -1081,8 +1088,11 @@ static void scsiback_do_1lun_hotplug(str
        err = xenbus_scanf(XBT_NIL, dev->nodename, str, "%u:%u:%u:%u",
                           &vir.hst, &vir.chn, &vir.tgt, &vir.lun);
        if (XENBUS_EXIST_ERR(err)) {
-               xenbus_printf(XBT_NIL, dev->nodename, state,
+               err = xenbus_printf(XBT_NIL, dev->nodename, state,
                              "%d", XenbusStateClosed);
+               if (err)
+                       xenbus_dev_error(info->dev, err,
+                               "%s: writing %s", __func__, state);
                return;
        }