[Xen-devel] [PATCH] linux: Add more consistency checking to balloon code

["Jan Beulich" <jbeulich@xxxxxxxxxx>]

.. to catch possible problems earlier. This is only a suggested patch,
not one strictly required.

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

Index: head-2007-02-27/drivers/xen/balloon/balloon.c
===================================================================
--- head-2007-02-27.orig/drivers/xen/balloon/balloon.c  2007-01-29 
12:22:44.000000000 +0100
+++ head-2007-02-27/drivers/xen/balloon/balloon.c       2007-03-12 
09:27:46.000000000 +0100
@@ -106,6 +106,8 @@ static struct timer_list balloon_timer;
 /* balloon_append: add the given page to the balloon. */
 static void balloon_append(struct page *page)
 {
+       BUG_ON(!PageReserved(page));
+
        /* Lowmem is re-populated first, so highmem pages go at list tail. */
        if (PageHighMem(page)) {
                list_add_tail(PAGE_TO_LIST(page), &ballooned_pages);
@@ -132,6 +134,8 @@ static struct page *balloon_retrieve(voi
        else
                bs.balloon_low--;
 
+       BUG_ON(!PageReserved(page));
+
        return page;
 }
 
@@ -293,6 +297,7 @@ static int decrease_reservation(unsigned
        for (i = 0; i < nr_pages; i++) {
                pfn = mfn_to_pfn(frame_list[i]);
                set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
+               SetPageReserved(pfn_to_page(pfn));
                balloon_append(pfn_to_page(pfn));
        }
 
@@ -483,6 +488,7 @@ static int __init balloon_init(void)
        for (pfn = xen_start_info->nr_pages; pfn < max_pfn; pfn++) {
                page = pfn_to_page(pfn);
                if (!PageReserved(page))
+                       SetPageReserved(page),
                        balloon_append(page);
        }
 #endif
@@ -560,6 +566,8 @@ struct page **alloc_empty_pages_and_page
                } else {
                        ret = apply_to_page_range(&init_mm, vaddr, PAGE_SIZE,
                                                  dealloc_pte_fn, NULL);
+                       if (ret == 0)
+                               SetPageReserved(page);
                }
 
                if (ret != 0) {
@@ -599,6 +607,7 @@ static void free_empty_pages_and_pageve
        balloon_lock(flags);
        for (i = 0; i < nr_pages; i++) {
                BUG_ON(page_count(pagevec[i]) != 1);
+               set_phys_to_machine(page_to_pfn(pagevec[i]), INVALID_P2M_ENTRY);
                balloon_append(pagevec[i]);
        }
        balloon_unlock(flags);
@@ -613,6 +622,7 @@ void balloon_release_driver_page(struct 
        unsigned long flags;
 
        balloon_lock(flags);
+       set_phys_to_machine(page_to_pfn(page), INVALID_P2M_ENTRY);
        balloon_append(page);
        bs.driver_pages--;
        balloon_unlock(flags);



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