[PATCH] xen/scsiback: don't call scsiback_free_translation_entry() under lock

[Juergen Gross <jgross@xxxxxxxx>]

scsiback_free_translation_entry() shouldn't be called under spinlock,
as it can sleep.

This requires to split removing a translation entry from the v2p list
from actually calling kref_put() for the entry.

Reported-by: Dan Carpenter <error27@xxxxxxxxx>
Link: https://lore.kernel.org/lkml/Y+JUIl64UDmdkboh@kadam/
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
 drivers/xen/xen-scsiback.c | 27 ++++++++++++++-------------
 1 file changed, 14 insertions(+), 13 deletions(-)

diff --git a/drivers/xen/xen-scsiback.c b/drivers/xen/xen-scsiback.c
index 954188b0b858..294f29cdc7aa 100644
--- a/drivers/xen/xen-scsiback.c
+++ b/drivers/xen/xen-scsiback.c
@@ -1010,12 +1010,6 @@ static int scsiback_add_translation_entry(struct 
vscsibk_info *info,
        return err;
 }
 
-static void __scsiback_del_translation_entry(struct v2p_entry *entry)
-{
-       list_del(&entry->l);
-       kref_put(&entry->kref, scsiback_free_translation_entry);
-}
-
 /*
   Delete the translation entry specified
 */
@@ -1024,18 +1018,20 @@ static int scsiback_del_translation_entry(struct 
vscsibk_info *info,
 {
        struct v2p_entry *entry;
        unsigned long flags;
-       int ret = 0;
 
        spin_lock_irqsave(&info->v2p_lock, flags);
        /* Find out the translation entry specified */
        entry = scsiback_chk_translation_entry(info, v);
        if (entry)
-               __scsiback_del_translation_entry(entry);
-       else
-               ret = -ENOENT;
+               list_del(&entry->l);
 
        spin_unlock_irqrestore(&info->v2p_lock, flags);
-       return ret;
+
+       if (!entry)
+               return -ENOENT;
+
+       kref_put(&entry->kref, scsiback_free_translation_entry);
+       return 0;
 }
 
 static void scsiback_do_add_lun(struct vscsibk_info *info, const char *state,
@@ -1239,14 +1235,19 @@ static void scsiback_release_translation_entry(struct 
vscsibk_info *info)
 {
        struct v2p_entry *entry, *tmp;
        struct list_head *head = &(info->v2p_entry_lists);
+       struct list_head tmp_list;
        unsigned long flags;
 
        spin_lock_irqsave(&info->v2p_lock, flags);
 
-       list_for_each_entry_safe(entry, tmp, head, l)
-               __scsiback_del_translation_entry(entry);
+       list_cut_before(&tmp_list, head, head);
 
        spin_unlock_irqrestore(&info->v2p_lock, flags);
+
+       list_for_each_entry_safe(entry, tmp, &tmp_list, l) {
+               list_del(&entry->l);
+               kref_put(&entry->kref, scsiback_free_translation_entry);
+       }
 }
 
 static void scsiback_remove(struct xenbus_device *dev)
-- 
2.35.3