Commit:     ce7e9fae8db07af4080e868f4588f8f095f803dc
Parent:     b8e7a54cd06b0b0174029ef3a7f5a1415a2c28f2
Author:     Christian Borntraeger <[EMAIL PROTECTED]>
AuthorDate: Tue Nov 20 11:13:36 2007 +0100
Committer:  Martin Schwidefsky <[EMAIL PROTECTED]>
CommitDate: Tue Nov 20 11:13:46 2007 +0100

    [S390] Optimize storage key handling for anonymous pages
    page_mkclean used to call page_clear_dirty for every given page. This
    is different to all other architectures, where the dirty bit in the
    PTEs is only resetted, if page_mapping() returns a non-NULL pointer.
    We can move the page_test_dirty/page_clear_dirty sequence into the
    2nd if to avoid unnecessary iske/sske sequences, which are expensive.
    This change also helps kvm for s390 as the host must transfer the
    dirty bit into the guest status bits. By moving the page_clear_dirty
    operation into the 2nd if, the vm will only call page_clear_dirty
    for pages where it walks the mapping anyway. There it calls
    ptep_clear_flush for writable ptes, so we can transfer the dirty bit
    to the guest.
    Signed-off-by: Christian Borntraeger <[EMAIL PROTECTED]>
    Signed-off-by: Martin Schwidefsky <[EMAIL PROTECTED]>
 mm/rmap.c |    9 +++++----
 1 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/mm/rmap.c b/mm/rmap.c
index dc3be5f..dbc2ca2 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -471,11 +471,12 @@ int page_mkclean(struct page *page)
        if (page_mapped(page)) {
                struct address_space *mapping = page_mapping(page);
-               if (mapping)
+               if (mapping) {
                        ret = page_mkclean_file(mapping, page);
-               if (page_test_dirty(page)) {
-                       page_clear_dirty(page);
-                       ret = 1;
+                       if (page_test_dirty(page)) {
+                               page_clear_dirty(page);
+                               ret = 1;
+                       }
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