2021-04-10 07:26:11

by Miaohe Lin

Subject: [PATCH v2 2/5] mm/hugeltb: simplify the return code of __vma_reservation_common()

It's guaranteed that the vma is associated with a resv_map, i.e. either
VM_MAYSHARE or HPAGE_RESV_OWNER, when the code reaches here or we would
have returned via !resv check above. So it's unneeded to check whether
HPAGE_RESV_OWNER is set here. Simplify the return code to make it more
clear.

Signed-off-by: Miaohe Lin <[email protected]>
---
mm/hugetlb.c | 41 ++++++++++++++++++++---------------------
1 file changed, 20 insertions(+), 21 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index a03a50b7c410..9b4c05699a90 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2163,27 +2163,26 @@ static long __vma_reservation_common(struct hstate *h,

if (vma->vm_flags & VM_MAYSHARE)
return ret;
- else if (is_vma_resv_set(vma, HPAGE_RESV_OWNER) && ret >= 0) {
- /*
- * In most cases, reserves always exist for private mappings.
- * However, a file associated with mapping could have been
- * hole punched or truncated after reserves were consumed.
- * As subsequent fault on such a range will not use reserves.
- * Subtle - The reserve map for private mappings has the
- * opposite meaning than that of shared mappings. If NO
- * entry is in the reserve map, it means a reservation exists.
- * If an entry exists in the reserve map, it means the
- * reservation has already been consumed. As a result, the
- * return value of this routine is the opposite of the
- * value returned from reserve map manipulation routines above.
- */
- if (ret)
- return 0;
- else
- return 1;
- }
- else
- return ret < 0 ? ret : 0;
+ /*
+ * We know private mapping must have HPAGE_RESV_OWNER set.
+ *
+ * In most cases, reserves always exist for private mappings.
+ * However, a file associated with mapping could have been
+ * hole punched or truncated after reserves were consumed.
+ * As subsequent fault on such a range will not use reserves.
+ * Subtle - The reserve map for private mappings has the
+ * opposite meaning than that of shared mappings. If NO
+ * entry is in the reserve map, it means a reservation exists.
+ * If an entry exists in the reserve map, it means the
+ * reservation has already been consumed. As a result, the
+ * return value of this routine is the opposite of the
+ * value returned from reserve map manipulation routines above.
+ */
+ if (ret > 0)
+ return 0;
+ if (ret == 0)
+ return 1;
+ return ret;
}

static long vma_needs_reservation(struct hstate *h,
--
2.19.1

2021-04-13 06:28:47

by Mike Kravetz

Subject: Re: [PATCH v2 2/5] mm/hugeltb: simplify the return code of __vma_reservation_common()

On 4/10/21 12:23 AM, Miaohe Lin wrote:
> It's guaranteed that the vma is associated with a resv_map, i.e. either
> VM_MAYSHARE or HPAGE_RESV_OWNER, when the code reaches here or we would
> have returned via !resv check above. So it's unneeded to check whether
> HPAGE_RESV_OWNER is set here. Simplify the return code to make it more
> clear.
>
> Signed-off-by: Miaohe Lin <[email protected]>

Thanks,

Reviewed-by: Mike Kravetz <[email protected]>
--
Mike Kravetz