xen/scsiback: avoid warnings when adding multiple LUNs to a domain

When adding more than one LUN to a frontend a warning for a failed
assignment is issued in dom0 for each already existing LUN. Avoid this
warning by checking for a LUN already existing when existence is
allowed (scsiback_do_add_lun() called with try == 1).

As the LUN existence check is needed now for a third time, factor it
out into a function. This in turn leads to a more or less complete
rewrite of scsiback_del_translation_entry() which will now return a
proper error code in case of failure.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>

1 files changed, 41 insertions, 29 deletions

diff --git a/drivers/xen/xen-scsiback.c b/drivers/xen/xen-scsiback.c
index 51387d75c7bf..c46ee189466f 100644
--- a/drivers/xen/xen-scsiback.c
+++ b/drivers/xen/xen-scsiback.c
@@ -849,15 +849,31 @@ static int scsiback_map(struct vscsibk_info *info)
 }
 
 /*
+  Check for a translation entry being present
+*/
+static struct v2p_entry *scsiback_chk_translation_entry(
+        struct vscsibk_info *info, struct ids_tuple *v)
+{
+        struct list_head *head = &(info->v2p_entry_lists);
+        struct v2p_entry *entry;
+
+        list_for_each_entry(entry, head, l)
+                if ((entry->v.chn == v->chn) &&
+                    (entry->v.tgt == v->tgt) &&
+                    (entry->v.lun == v->lun))
+                        return entry;
+
+        return NULL;
+}
+
+/*
   Add a new translation entry
 */
 static int scsiback_add_translation_entry(struct vscsibk_info *info,
                                           char *phy, struct ids_tuple *v)
 {
         int err = 0;
-        struct v2p_entry *entry;
         struct v2p_entry *new;
-        struct list_head *head = &(info->v2p_entry_lists);
         unsigned long flags;
         char *lunp;
         unsigned long long unpacked_lun;
@@ -917,15 +933,10 @@ static int scsiback_add_translation_entry(struct vscsibk_info *info,
         spin_lock_irqsave(&info->v2p_lock, flags);
 
         /* Check double assignment to identical virtual ID */
-        list_for_each_entry(entry, head, l) {
-                if ((entry->v.chn == v->chn) &&
-                    (entry->v.tgt == v->tgt) &&
-                    (entry->v.lun == v->lun)) {
-                        pr_warn("Virtual ID is already used. Assignment was not performed.\n");
-                        err = -EEXIST;
-                        goto out;
-                }
-
+        if (scsiback_chk_translation_entry(info, v)) {
+                pr_warn("Virtual ID is already used. Assignment was not performed.\n");
+                err = -EEXIST;
+                goto out;
         }
 
         /* Create a new translation entry and add to the list */
@@ -933,7 +944,7 @@ static int scsiback_add_translation_entry(struct vscsibk_info *info,
         new->v = *v;
         new->tpg = tpg;
         new->lun = unpacked_lun;
-        list_add_tail(&new->l, head);
+        list_add_tail(&new->l, &info->v2p_entry_lists);
 
 out:
         spin_unlock_irqrestore(&info->v2p_lock, flags);
@@ -956,39 +967,40 @@ static void __scsiback_del_translation_entry(struct v2p_entry *entry)
 }
 
 /*
-  Delete the translation entry specfied
+  Delete the translation entry specified
 */
 static int scsiback_del_translation_entry(struct vscsibk_info *info,
                                           struct ids_tuple *v)
 {
         struct v2p_entry *entry;
-        struct list_head *head = &(info->v2p_entry_lists);
         unsigned long flags;
+        int ret = 0;
 
         spin_lock_irqsave(&info->v2p_lock, flags);
         /* Find out the translation entry specified */
-        list_for_each_entry(entry, head, l) {
-                if ((entry->v.chn == v->chn) &&
-                    (entry->v.tgt == v->tgt) &&
-                    (entry->v.lun == v->lun)) {
-                        goto found;
-                }
-        }
-
-        spin_unlock_irqrestore(&info->v2p_lock, flags);
-        return 1;
-
-found:
-        /* Delete the translation entry specfied */
-        __scsiback_del_translation_entry(entry);
+        entry = scsiback_chk_translation_entry(info, v);
+        if (entry)
+                __scsiback_del_translation_entry(entry);
+        else
+                ret = -ENOENT;
 
         spin_unlock_irqrestore(&info->v2p_lock, flags);
-        return 0;
+        return ret;
 }
 
 static void scsiback_do_add_lun(struct vscsibk_info *info, const char *state,
                                 char *phy, struct ids_tuple *vir, int try)
 {
+        struct v2p_entry *entry;
+        unsigned long flags;
+
+        if (try) {
+                spin_lock_irqsave(&info->v2p_lock, flags);
+                entry = scsiback_chk_translation_entry(info, vir);
+                spin_unlock_irqrestore(&info->v2p_lock, flags);
+                if (entry)
+                        return;
+        }
         if (!scsiback_add_translation_entry(info, phy, vir)) {
                 if (xenbus_printf(XBT_NIL, info->dev->nodename, state,
                                   "%d", XenbusStateInitialised)) {