lkml.org 
[lkml]   [2019]   [Aug]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] vfio/type1: avoid redundant PageReserved checking
On Tue, 27 Aug 2019 20:49:48 +0800
Ben Luo <luoben@linux.alibaba.com> wrote:

> currently, if the page is not a tail of compound page, it will be
> checked twice for the same thing.
>
> Signed-off-by: Ben Luo <luoben@linux.alibaba.com>
> ---
> drivers/vfio/vfio_iommu_type1.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 054391f..cbe0d88 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -291,11 +291,10 @@ static int vfio_lock_acct(struct vfio_dma *dma, long npage, bool async)
> static bool is_invalid_reserved_pfn(unsigned long pfn)
> {
> if (pfn_valid(pfn)) {
> - bool reserved;
> struct page *tail = pfn_to_page(pfn);
> struct page *head = compound_head(tail);
> - reserved = !!(PageReserved(head));
> if (head != tail) {
> + bool reserved = !!(PageReserved(head));
> /*
> * "head" is not a dangling pointer
> * (compound_head takes care of that)
> @@ -310,7 +309,7 @@ static bool is_invalid_reserved_pfn(unsigned long pfn)
> if (PageTail(tail))
> return reserved;
> }
> - return PageReserved(tail);
> + return !!(PageReserved(tail));
> }
>
> return true;

Logic seems fine to me, though I'd actually prefer to get rid of the !!
in the first use than duplicate it at the second use. Thanks,

Alex

\
 
 \ /
  Last update: 2019-08-27 20:41    [W:0.122 / U:0.044 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site