At present, PG_dcache_clean is only cleared when the related huge page
is about to be freed. But sometimes, there maybe a process is in charge
to copy binary codes into a shared memory, and notifies other processes
to execute base on that. For the first time, there is no problem, because
the default value of page->flags is PG_dcache_clean cleared. So the cache
will be maintained at the time of set_pte_at for other processes. But if
the content of the shared memory have been updated again, there is no
cache operations, because the PG_dcache_clean is still set.
For example:
Process A
open a hugetlbfs file
mmap it as a shared memory
copy some binary codes into it
munmap
Process B
open the hugetlbfs file
mmap it as a shared memory, executable
invoke the functions in the shared memory
munmap
repeat the above steps.
Signed-off-by: Zhen Lei <[email protected]>
---
arch/arm64/mm/hugetlbpage.c | 20 +++++++++++++++-----
1 file changed, 15 insertions(+), 5 deletions(-)
diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
index 2e49bd2..547b158 100644
--- a/arch/arm64/mm/hugetlbpage.c
+++ b/arch/arm64/mm/hugetlbpage.c
@@ -201,6 +201,7 @@ pte_t huge_ptep_get_and_clear(struct mm_struct *mm,
unsigned long addr, pte_t *ptep)
{
pte_t pte;
+ struct page *page;
if (pte_cont(*ptep)) {
int ncontig, i;
@@ -222,12 +223,21 @@ pte_t huge_ptep_get_and_clear(struct mm_struct *mm,
if (pte_dirty(ptep_get_and_clear(mm, addr, cpte)))
is_dirty = true;
}
- if (is_dirty)
- return pte_mkdirty(pte);
- else
- return pte;
+ if (is_dirty) {
+ pte = pte_mkdirty(pte);
+ page = pte_page(pte);
+ clear_bit(PG_dcache_clean, &page->flags);
+ }
+
+ return pte;
} else {
- return ptep_get_and_clear(mm, addr, ptep);
+ pte = ptep_get_and_clear(mm, addr, ptep);
+ if (huge_pte_dirty(pte)) {
+ page = pte_page(pte);
+ clear_bit(PG_dcache_clean, &page->flags);
+ }
+
+ return pte;
}
}
--
2.5.0
