From: Martin Schwidefsky <schwidefsky@de.ibm.com>
Fix endless loop in get_user_pages() on s390. It happens only on s/390
because pte_dirty always returns 0. For all other architectures this is an
optimization.
In the case of "write && !pte_dirty(pte)" follow_page() returns NULL. On all
architectures except s390 handle_pte_fault() will then create a pte with
pte_dirty(pte)==1 because write_access==1. In the following, second call to
follow_page() all is fine. With the physical dirty bit patch pte_dirty() is
always 0 for s/390 because the dirty bit doesn't live in the pte.
---
mm/memory.c | 21 +++++++++++++--------
1 files changed, 13 insertions(+), 8 deletions(-)
diff -puN mm/memory.c~s390-16-follow_page-lockup-fix mm/memory.c
--- 25/mm/memory.c~s390-16-follow_page-lockup-fix 2004-01-09 00:20:23.000000000 -0800
+++ 25-akpm/mm/memory.c 2004-01-09 00:53:12.000000000 -0800
@@ -656,14 +656,19 @@ follow_page(struct mm_struct *mm, unsign
pte = *ptep;
pte_unmap(ptep);
if (pte_present(pte)) {
- if (!write || (pte_write(pte) && pte_dirty(pte))) {
- pfn = pte_pfn(pte);
- if (pfn_valid(pfn)) {
- struct page *page = pfn_to_page(pfn);
-
- mark_page_accessed(page);
- return page;
- }
+ 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);
+
+ mark_page_accessed(page);
+ return page;
}
}
_