[Xen-changelog] [xen master] mem_sharing_nominate_page: p2mt should never change before p2m_change_type()

[patchbot@xxxxxxx]

commit fa89d08f329e495f20a561a0dac80c325c8b7784
Author:     Nai Xia <nai.xia@xxxxxxxxx>
AuthorDate: Wed Aug 7 00:25:48 2013 +0800
Commit:     Tim Deegan <tim@xxxxxxx>
CommitDate: Thu Aug 8 11:19:46 2013 +0100

    mem_sharing_nominate_page: p2mt should never change before p2m_change_type()
    
    The p2mt change check for p2m_change_type() was first introduced when
    this code path was not protected by p2m_lock().  Now this code path is
    protected by p2m_lock. So p2mt should never change before
    p2m_change_type().
    
    Signed-off-by: Nai Xia <nai.xia@xxxxxxxxx>
    Acked-by: Andres Lagar-Cavilla <andres@xxxxxxxxxxxxxxxx>
    Acked-by: Tim Deegan <tim@xxxxxxx>
---
 xen/arch/x86/mm/mem_sharing.c |   16 ++--------------
 1 files changed, 2 insertions(+), 14 deletions(-)

diff --git a/xen/arch/x86/mm/mem_sharing.c b/xen/arch/x86/mm/mem_sharing.c
index 0364bb0..1e89f6c 100644
--- a/xen/arch/x86/mm/mem_sharing.c
+++ b/xen/arch/x86/mm/mem_sharing.c
@@ -900,20 +900,8 @@ int mem_sharing_nominate_page(struct domain *d,
         goto out;
     }
 
-    /* Change the p2m type */
-    if ( p2m_change_type(d, gfn, p2mt, p2m_ram_shared) != p2mt ) 
-    {
-        /* This is unlikely, as the type must have changed since we've checked
-         * it a few lines above.
-         * The mfn needs to revert back to rw type. This should never fail,
-         * since no-one knew that the mfn was temporarily sharable */
-        mem_sharing_gfn_destroy(page, d, gfn_info);
-        xfree(page->sharing);
-        page->sharing = NULL;
-        /* NOTE: We haven't yet added this to the audit list. */
-        BUG_ON(page_make_private(d, page) != 0);
-        goto out;
-    }
+    /* Change the p2m type, should never fail with p2m locked. */
+    BUG_ON(p2m_change_type(d, gfn, p2mt, p2m_ram_shared) != p2mt);
 
     /* Account for this page. */
     atomic_inc(&nr_shared_mfns);
--
generated by git-patchbot for /home/xen/git/xen.git#master

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