[Xen-changelog] [xen master] x86: use switch() in _put_page_type()

[patchbot@xxxxxxx]

commit 40df03fc6ff8410b3d9aa2e7bb5163b698c39b3e
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Fri Dec 15 11:15:54 2017 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Dec 15 11:15:54 2017 +0100

    x86: use switch() in _put_page_type()
    
    Use this to cheaply add another assertion.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 xen/arch/x86/mm.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index 53a211e..b8eb4fe 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -2458,8 +2458,9 @@ static int _put_page_type(struct page_info *page, bool 
preemptible,
 
         ASSERT((x & PGT_count_mask) != 0);
 
-        if ( unlikely((nx & PGT_count_mask) == 0) )
+        switch ( nx & (PGT_locked | PGT_count_mask) )
         {
+        case 0:
             if ( unlikely((nx & PGT_type_mask) <= PGT_l4_page_table) &&
                  likely(nx & (PGT_validated|PGT_partial)) )
             {
@@ -2495,10 +2496,14 @@ static int _put_page_type(struct page_info *page, bool 
preemptible,
             }
             else
                 BUG_ON(!IS_ENABLED(CONFIG_PV_LINEAR_PT));
-        }
-        else if ( unlikely((nx & (PGT_locked | PGT_count_mask)) ==
-                           (PGT_locked | 1)) )
-        {
+
+            break;
+
+        case PGT_locked:
+            ASSERT_UNREACHABLE();
+            return -EILSEQ;
+
+        case PGT_locked | 1:
             /*
              * We must not drop the second to last reference when the page is
              * locked, as page_unlock() doesn't do any cleanup of the type.
--
generated by git-patchbot for /home/xen/git/xen.git#master

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