Currently if copy_nonpresent_pte() returns a non-zero value it is assumed to be a swap entry which requires further processing outside the loop in copy_pte_range() after dropping locks. This prevents other values being returned to signal conditions such as failure which a subsequent change requires.
Instead make copy_nonpresent_pte() return an error code if further processing is required and read the value for the swap entry in the main loop under the ptl. Signed-off-by: Alistair Popple <[email protected]> --- v9: New for v9 to allow device exclusive handling to occur in copy_nonpresent_pte(). --- mm/memory.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 2fb455c365c2..e061cfa18c11 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -718,7 +718,7 @@ copy_nonpresent_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm, if (likely(!non_swap_entry(entry))) { if (swap_duplicate(entry) < 0) - return entry.val; + return -EAGAIN; /* make sure dst_mm is on swapoff's mmlist. */ if (unlikely(list_empty(&dst_mm->mmlist))) { @@ -974,11 +974,13 @@ copy_pte_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma, continue; } if (unlikely(!pte_present(*src_pte))) { - entry.val = copy_nonpresent_pte(dst_mm, src_mm, - dst_pte, src_pte, - src_vma, addr, rss); - if (entry.val) + ret = copy_nonpresent_pte(dst_mm, src_mm, + dst_pte, src_pte, + src_vma, addr, rss); + if (ret == -EAGAIN) { + entry = pte_to_swp_entry(*src_pte); break; + } progress += 8; continue; } -- 2.20.1
