On 10/01/2012 10:59 PM, Andrea Arcangeli wrote:
Hi Will, On Mon, Oct 01, 2012 at 02:51:45PM +0100, Will Deacon wrote:+void huge_pmd_set_accessed(struct mm_struct *mm, struct vm_area_struct *vma, + unsigned long address, pmd_t *pmd, pmd_t orig_pmd) +{ + pmd_t entry; + + spin_lock(&mm->page_table_lock); + entry = pmd_mkyoung(orig_pmd); + if (pmdp_set_access_flags(vma, address & HPAGE_PMD_MASK, pmd, entry, 0)) + update_mmu_cache(vma, address, pmd);If the pmd is being splitted, this may not be a trasnhuge pmd anymore by the time you obtained the lock. (orig_pmd could be stale, and it wasn't verified with pmd_same either)
Could you tell me when should call pmd_same in general?
The lock should be obtained through pmd_trans_huge_lock. if (pmd_trans_huge_lock(orig_pmd, vma) == 1) { set young bit spin_unlock(&mm->page_table_lock); } On x86: int pmdp_set_access_flags(struct vm_area_struct *vma, unsigned long address, pmd_t *pmdp, pmd_t entry, int dirty) { int changed = !pmd_same(*pmdp, entry); VM_BUG_ON(address & ~HPAGE_PMD_MASK); if (changed && dirty) { *pmdp = entry; with dirty == 0 it looks like it won't make any difference, but I guess your arm pmdp_set_access_flag is different. However it seems "dirty" means write access and so the invocation would better match the pte case: if (pmdp_set_access_flags(vma, address & HPAGE_PMD_MASK, pmd, entry, flags & FAULT_FLAG_WRITE)) But note, you still have to update it even when "dirty" == 0, or it'll still infinite loop for read accesses.+ spin_unlock(&mm->page_table_lock); +} + int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, pmd_t *pmd, pmd_t orig_pmd) { diff --git a/mm/memory.c b/mm/memory.c index 5736170..d5c007d 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3537,7 +3537,11 @@ retry: if (unlikely(ret & VM_FAULT_OOM)) goto retry; return ret; + } else { + huge_pmd_set_accessed(mm, vma, address, pmd, + orig_pmd); } + return 0;Thanks, Andrea -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
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