[Xen-devel] [PATCH] introduce page_list_move()

["Jan Beulich" <JBeulich@xxxxxxxxxx>]

This not only allows to remove ia64's special implementation of
page_list_splice_init(), but also fixes the latent issue with the
direct list head assignment in the x86 code if that would ever get
switched back to using normal list entries for linking together pages
(i.e. whenever x86-64 is to support more tha 16Tb of memory).

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>

--- 2009-06-10.orig/xen/arch/ia64/xen/domain.c  2009-06-10 10:48:29.000000000 
+0200
+++ 2009-06-10/xen/arch/ia64/xen/domain.c       2009-06-17 16:04:07.000000000 
+0200
@@ -1705,7 +1705,7 @@ static int relinquish_memory(struct doma
         }
     }
 
-    page_list_splice_init(&d->arch.relmem_list, list);
+    page_list_move(list, &d->arch.relmem_list);
 
  out:
     spin_unlock_recursive(&d->page_alloc_lock);
--- 2009-06-10.orig/xen/arch/x86/domain.c       2009-05-25 08:44:00.000000000 
+0200
+++ 2009-06-10/xen/arch/x86/domain.c    2009-06-17 16:04:46.000000000 +0200
@@ -1780,11 +1780,7 @@ static int relinquish_memory(
     }
 
     /* list is empty at this point. */
-    if ( !page_list_empty(&d->arch.relmem_list) )
-    {
-        *list = d->arch.relmem_list;
-        INIT_PAGE_LIST_HEAD(&d->arch.relmem_list);
-    }
+    page_list_move(list, &d->arch.relmem_list);
 
  out:
     spin_unlock_recursive(&d->page_alloc_lock);
--- 2009-06-10.orig/xen/include/asm-ia64/mm.h   2009-05-27 13:54:07.000000000 
+0200
+++ 2009-06-10/xen/include/asm-ia64/mm.h        2009-06-17 16:03:46.000000000 
+0200
@@ -92,24 +92,6 @@ struct page_info
     u32 tlbflush_timestamp;
 };
 
-#ifndef page_list_entry
-static inline void
-page_list_splice_init(struct page_list_head *list, struct page_list_head *head)
-{
-    if ( !page_list_empty(list) )
-    {
-        if ( head->next )
-            head->tail->list.next = page_to_mfn(list->next);
-        else
-            head->next = list->next;
-        head->tail = list->tail;
-        INIT_PAGE_LIST_HEAD(list);
-    }
-}
-#else
-# define page_list_splice_init list_splice_init
-#endif
-
 #define set_page_count(p,v)    atomic_set(&(p)->_count, v - 1)
 
 /*
--- 2009-06-10.orig/xen/include/xen/mm.h        2009-05-27 13:54:07.000000000 
+0200
+++ 2009-06-10/xen/include/xen/mm.h     2009-06-17 16:02:28.000000000 +0200
@@ -223,7 +223,15 @@ page_list_remove_head(struct page_list_h
 
     return page;
 }
-
+static inline void
+page_list_move(struct page_list_head *dst, struct page_list_head *src)
+{
+    if ( !page_list_empty(src) )
+    {
+        *dst = *src;
+        INIT_PAGE_LIST_HEAD(src);
+    }
+}
 static inline void
 page_list_splice(struct page_list_head *list, struct page_list_head *head)
 {
@@ -281,6 +289,8 @@ page_list_splice(struct page_list_head *
         list_del(&__pg->list); \
         __pg; \
     }) : NULL)
+# define page_list_move(dst, src)        (!list_empty(src) ? \
+    list_replace_init(src, dst) : (void)0)
 # define page_list_for_each(pos, head)   list_for_each_entry(pos, head, list)
 # define page_list_for_each_safe(pos, tmp, head) \
     list_for_each_entry_safe(pos, tmp, head, list)




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