[Xen-devel] [PATCH v2 2/2] xen/scsiback: avoid warnings when adding multiple LUNs to a domain

[Juergen Gross <jgross@xxxxxxxx>]

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@xxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
v2: scsiback_del_translation_entry() returns error code instead of 1
    (Boris Ostrovsky)
---
 drivers/xen/xen-scsiback.c | 70 +++++++++++++++++++++++++++-------------------
 1 file changed, 41 insertions(+), 29 deletions(-)

diff --git a/drivers/xen/xen-scsiback.c b/drivers/xen/xen-scsiback.c
index 51387d7..c46ee18 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)) {
-- 
2.6.2


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