[Xen-devel] [PATCH] eliminate some special page list accessors

["Jan Beulich" <jbeulich@xxxxxxxxxx>]

Since page_list_move_tail(), page_list_splice_init(), and
page_list_is_eol() are only used by relinquish_memory(), and that
function can easily be changed to use more generic accessors, just
eliminate them altogether.

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

--- 2009-01-30.orig/xen/arch/x86/domain.c       2009-01-30 10:22:31.000000000 
+0100
+++ 2009-01-30/xen/arch/x86/domain.c    2009-02-04 11:19:13.000000000 +0100
@@ -1666,23 +1666,20 @@ int hypercall_xlat_continuation(unsigned
 static int relinquish_memory(
     struct domain *d, struct page_list_head *list, unsigned long type)
 {
-    struct page_info  *page, *cur;
+    struct page_info  *page;
     unsigned long     x, y;
     int               ret = 0;
 
     /* Use a recursive lock, as we may enter 'free_domheap_page'. */
     spin_lock_recursive(&d->page_alloc_lock);
 
-    page = page_list_first(list);
-    while ( !page_list_is_eol(page, list) )
+    while ( (page = page_list_remove_head(list)) )
     {
         /* Grab a reference to the page so it won't disappear from under us. */
         if ( unlikely(!get_page(page, d)) )
         {
             /* Couldn't get a reference -- someone is freeing this page. */
-            cur = page;
-            page = page_list_next(page, list);
-            page_list_move_tail(cur, list, &d->arch.relmem_list);
+            page_list_add_tail(page, &d->arch.relmem_list);
             continue;
         }
 
@@ -1694,6 +1691,7 @@ static int relinquish_memory(
             break;
         case -EAGAIN:
         case -EINTR:
+            page_list_add(page, list);
             set_bit(_PGT_pinned, &page->u.inuse.type_info);
             put_page(page);
             goto out;
@@ -1730,6 +1728,7 @@ static int relinquish_memory(
                 case 0:
                     break;
                 case -EINTR:
+                    page_list_add(page, list);
                     page->u.inuse.type_info |= PGT_validated;
                     if ( x & PGT_partial )
                         put_page(page);
@@ -1737,6 +1736,7 @@ static int relinquish_memory(
                     ret = -EAGAIN;
                     goto out;
                 case -EAGAIN:
+                    page_list_add(page, list);
                     page->u.inuse.type_info |= PGT_partial;
                     if ( x & PGT_partial )
                         put_page(page);
@@ -1753,11 +1753,9 @@ static int relinquish_memory(
             }
         }
 
-        /* Follow the list chain and /then/ potentially free the page. */
-        cur = page;
-        page = page_list_next(page, list);
-        page_list_move_tail(cur, list, &d->arch.relmem_list);
-        put_page(cur);
+        /* Put the page on the list and /then/ potentially free it. */
+        page_list_add_tail(page, &d->arch.relmem_list);
+        put_page(page);
 
         if ( hypercall_preempt_check() )
         {
@@ -1766,7 +1764,12 @@ static int relinquish_memory(
         }
     }
 
-    page_list_splice_init(&d->arch.relmem_list, list);
+    /* 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);
+    }
 
  out:
     spin_unlock_recursive(&d->page_alloc_lock);
--- 2009-01-30.orig/xen/include/xen/mm.h        2009-01-30 10:13:53.000000000 
+0100
+++ 2009-01-30/xen/include/xen/mm.h     2009-02-04 10:59:39.000000000 +0100
@@ -125,12 +125,6 @@ page_list_prev(const struct page_info *p
 {
     return page != head->next ? mfn_to_page(page->list.prev) : NULL;
 }
-static inline int
-page_list_is_eol(const struct page_info *page,
-                 const struct page_list_head *head)
-{
-    return !page;
-}
 static inline void
 page_list_add(struct page_info *page, struct page_list_head *head)
 {
@@ -214,13 +208,6 @@ page_list_del2(struct page_info *page, s
         prev->list.next = page->list.next;
     }
 }
-static inline void
-page_list_move_tail(struct page_info *page, struct page_list_head *list,
-                    struct page_list_head *head)
-{
-    page_list_del(page, list);
-    page_list_add_tail(page, head);
-}
 static inline struct page_info *
 page_list_remove_head(struct page_list_head *head)
 {
@@ -231,19 +218,6 @@ page_list_remove_head(struct page_list_h
 
     return page;
 }
-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);
-    }
-}
 
 #define page_list_for_each(pos, head) \
     for ( pos = (head)->next; pos; pos = page_list_next(pos, head) )
@@ -266,19 +240,16 @@ page_list_splice_init(struct page_list_h
                                                     struct page_info, list)
 # define page_list_next(pg, hd)          list_entry((pg)->list.next, \
                                                     struct page_info, list)
-# define page_list_is_eol(pg, hd)        (&(pg)->list == (hd))
 # define page_list_add(pg, hd)           list_add(&(pg)->list, hd)
 # define page_list_add_tail(pg, hd)      list_add_tail(&(pg)->list, hd)
 # define page_list_del(pg, hd)           list_del(&(pg)->list)
 # define page_list_del2(pg, hd1, hd2)    list_del(&(pg)->list)
-# define page_list_move_tail(pg, o, n)   list_move_tail(&(pg)->list, n)
 # define page_list_remove_head(hd)       (!page_list_empty(hd) ? \
     ({ \
         struct page_info *__pg = page_list_first(hd); \
         list_del(&__pg->list); \
         __pg; \
     }) : NULL)
-# define page_list_splice_init           list_splice_init
 # 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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