Re: [PATCH] aio: Cleanup unnecessary test for nr_pages
On 06/20/16 at 03:17P, Al Viro wrote:
> On Mon, Jun 20, 2016 at 10:05:45PM +0800, Minfei Huang wrote:
> > Ping. Any comment is appreciate.
> >
> > Thanks
> > Minfei
> >
> > On 06/13/16 at 12:33P, Minfei Huang wrote:
> > > The variable nr_pages is always more than 1, because the size of
> > > structure aio_ring is bigger than 0. So remove unnecessary test for
> > > nr_page.
>
> What this test really checks is that the value we'd put into nr_pages
> (PFN_UP(size)) is not greater than 2^31. Whether it's redundant or not
> is a separate question - it very well might be, due to the code in
> ioctx_alloc() that caps nr_events, but that needs a proof. In any case,
> the reasons you are offering in commit message are wrong - it's about
> size being too _large_, not too small.
Hmm. But there is a following test in function ioctx_alloc which is used
to limit the max of nr_events.
713 /* Prevent overflows */
714 if (nr_events > (0x1000U / sizeof(struct io_event))) {
715 pr_debug("ENOMEM: nr_events too high\n");
716 return ERR_PTR(-EINVAL);
717 }
So according to this test, we can make sure that nr_pages(PFN_UP(size))
cann't be greater than 2^31, and max to 2^28.
Thanks
Minfei
Re: [PATCH] aio: Cleanup unnecessary test for nr_pages
On Mon, Jun 20, 2016 at 10:05:45PM +0800, Minfei Huang wrote: > Ping. Any comment is appreciate. > > Thanks > Minfei > > On 06/13/16 at 12:33P, Minfei Huang wrote: > > The variable nr_pages is always more than 1, because the size of > > structure aio_ring is bigger than 0. So remove unnecessary test for > > nr_page. What this test really checks is that the value we'd put into nr_pages (PFN_UP(size)) is not greater than 2^31. Whether it's redundant or not is a separate question - it very well might be, due to the code in ioctx_alloc() that caps nr_events, but that needs a proof. In any case, the reasons you are offering in commit message are wrong - it's about size being too _large_, not too small.
Re: [PATCH] aio: Cleanup unnecessary test for nr_pages
Ping. Any comment is appreciate.
Thanks
Minfei
On 06/13/16 at 12:33P, Minfei Huang wrote:
> The variable nr_pages is always more than 1, because the size of
> structure aio_ring is bigger than 0. So remove unnecessary test for
> nr_page.
>
> Signed-off-by: Minfei Huang
> ---
> fs/aio.c | 2 --
> 1 file changed, 2 deletions(-)
>
> diff --git a/fs/aio.c b/fs/aio.c
> index fb8e45b..ec05137 100644
> --- a/fs/aio.c
> +++ b/fs/aio.c
> @@ -450,8 +450,6 @@ static int aio_setup_ring(struct kioctx *ctx)
> size += sizeof(struct io_event) * nr_events;
>
> nr_pages = PFN_UP(size);
> - if (nr_pages < 0)
> - return -EINVAL;
>
> file = aio_private_file(ctx, nr_pages);
> if (IS_ERR(file)) {
> --
> 2.7.4 (Apple Git-66)
>
[PATCH] aio: Cleanup unnecessary test for nr_pages
The variable nr_pages is always more than 1, because the size of
structure aio_ring is bigger than 0. So remove unnecessary test for
nr_page.
Signed-off-by: Minfei Huang
---
fs/aio.c | 2 --
1 file changed, 2 deletions(-)
diff --git a/fs/aio.c b/fs/aio.c
index fb8e45b..ec05137 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -450,8 +450,6 @@ static int aio_setup_ring(struct kioctx *ctx)
size += sizeof(struct io_event) * nr_events;
nr_pages = PFN_UP(size);
- if (nr_pages < 0)
- return -EINVAL;
file = aio_private_file(ctx, nr_pages);
if (IS_ERR(file)) {
--
2.7.4 (Apple Git-66)
