In copy_present_page, after we mark the pte non-writable, we should check for previous dirty bit updates and make sure we don't lose the dirty bit on reset.
Also, avoid marking the pte write-protected again if copy_present_page already marked it write-protected. Cc: Peter Xu <[email protected]> Cc: Jason Gunthorpe <[email protected]> Cc: John Hubbard <[email protected]> Cc: [email protected] Cc: [email protected] Cc: Andrew Morton <[email protected]> Cc: Jan Kara <[email protected]> Cc: Michal Hocko <[email protected]> Cc: Kirill Shutemov <[email protected]> Cc: Hugh Dickins <[email protected]> Cc: Linus Torvalds <[email protected]> Signed-off-by: Aneesh Kumar K.V <[email protected]> --- mm/memory.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/mm/memory.c b/mm/memory.c index bfe202ef6244..f57b1f04d50a 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -848,6 +848,9 @@ copy_present_page(struct mm_struct *dst_mm, struct mm_struct *src_mm, if (likely(!page_maybe_dma_pinned(page))) return 1; + if (pte_dirty(*src_pte)) + pte = pte_mkdirty(pte); + /* * Uhhuh. It looks like the page might be a pinned page, * and we actually need to copy it. Now we can set the @@ -904,6 +907,11 @@ copy_present_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm, if (retval <= 0) return retval; + /* + * Fetch the src pte value again, copy_present_page + * could modify it. + */ + pte = *src_pte; get_page(page); page_dup_rmap(page, false); rss[mm_counter(page)]++; -- 2.26.2
