If anon_vma is prepared unsuccessfully, new_page and old_page should be freed.
And due to that page_table_lock is re-acquired, race in updating page table
should also be check. If race does happen, our job is done.
All comments and ideas welcome.
Thanks
Signed-off-by: Hillf Danton <dhillf@xxxxxxxxx>
---
--- a/mm/hugetlb.c Sat Aug 13 11:45:14 2011
+++ b/mm/hugetlb.c Sat Oct 29 20:44:09 2011
@@ -2406,8 +2406,7 @@ retry_avoidcopy:
if (unmap_ref_private(mm, vma, old_page, address)) {
BUG_ON(page_count(old_page) != 1);
BUG_ON(huge_pte_none(pte));
- spin_lock(&mm->page_table_lock);
- goto retry_avoidcopy;
+ goto lock_and_check;
}
WARN_ON_ONCE(1);
}
@@ -2422,6 +2421,8 @@ retry_avoidcopy:
* anon_vma prepared.
*/
if (unlikely(anon_vma_prepare(vma))) {
+ page_cache_release(new_page);
+ page_cache_release(old_page);
/* Caller expects lock to be held */
spin_lock(&mm->page_table_lock);
return VM_FAULT_OOM;
@@ -2455,6 +2456,14 @@ retry_avoidcopy:
}
page_cache_release(new_page);
page_cache_release(old_page);
+ return 0;
+
+lock_and_check:
+ spin_lock(&mm->page_table_lock);
+ ptep = huge_pte_offset(mm, address & huge_page_mask(h));
+ if (likely(pte_same(huge_ptep_get(ptep), pte)))
+ goto retry_avoidcopy;
+ /* else changes occured while taking page_table_lock, our job done */
return 0;
}
--
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