[PATCH] follow_page invalid pte_page

[Hugh Dickins]

The follow_page write-access case is relying on pte_page before checking
pfn_valid: rearrange that - and we don't need three struct page *pages.

(I notice mempolicy.c's verify_pages is also relying on pte_page, but
I'll leave that to Andi: maybe it ought to be failing on, or skipping
over, VM_IO or VM_RESERVED vmas?)

Signed-off-by: Hugh Dickins <hugh@xxxxxxxxxxx>

 mm/memory.c |   10 +++-------
 1 files changed, 3 insertions(+), 7 deletions(-)

--- 2.6.7-rc2/mm/memory.c	2004-05-30 11:36:39.000000000 +0100
+++ linux/mm/memory.c	2004-06-02 16:31:33.037399304 +0100
@@ -637,15 +637,11 @@ follow_page(struct mm_struct *mm, unsign
 	if (pte_present(pte)) {
 		if (write && !pte_write(pte))
 			goto out;
-		if (write && !pte_dirty(pte)) {
-			struct page *page = pte_page(pte);
-			if (!PageDirty(page))
-				set_page_dirty(page);
-		}
 		pfn = pte_pfn(pte);
 		if (pfn_valid(pfn)) {
-			struct page *page = pfn_to_page(pfn);
-			
+			page = pfn_to_page(pfn);
+			if (write && !pte_dirty(pte) && !PageDirty(page))
+				set_page_dirty(page);
 			mark_page_accessed(page);
 			return page;
 		}

-
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