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From: Gavin Li <gavinli@thegavinli.com>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: linux-usb@vger.kernel.org, Gavin Li <git@thegavinli.com>
Subject: Re: [PATCH] usb: usbfs: only account once for mmap()'ed usb memory usage
Date: Thu, 15 Aug 2019 22:51:54 -0700
Message-ID: <CA+GxvY5+uyDrNM=XcfyhBXYvREf52YTfVb7FfcZa82jh_v08Dw@mail.gmail.com> (raw)
In-Reply-To: <20190815125314.GA24270@kroah.com>

It is done in usbdev_mmap(); it calls usbfs_increase_memory_usage() to
account for the buffer it allocates. No additional memory (other than
for the control structures) is needed when actually submitting the
URB.

On Thu, Aug 15, 2019 at 5:53 AM Greg KH <gregkh@linuxfoundation.org> wrote:
>
> On Wed, Aug 14, 2019 at 02:29:24PM -0700, gavinli@thegavinli.com wrote:
> > From: Gavin Li <git@thegavinli.com>
> >
> > Memory usage for USB memory allocated via mmap() is already accounted
> > for at mmap() time; no need to account for it again at submiturb time.
> >
> > Signed-off-by: Gavin Li <git@thegavinli.com>
> > ---
> >  drivers/usb/core/devio.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
>
> What commit does this fix?  What issue does this fix, is it something
> that is user-visable?
>
> >
> > diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
> > index bbe9c2edd3e7..9681dd55473b 100644
> > --- a/drivers/usb/core/devio.c
> > +++ b/drivers/usb/core/devio.c
> > @@ -1603,7 +1603,8 @@ static int proc_do_submiturb(struct usb_dev_state *ps, struct usbdevfs_urb *uurb
> >       if (as->usbm)
> >               num_sgs = 0;
> >
> > -     u += sizeof(struct async) + sizeof(struct urb) + uurb->buffer_length +
> > +     u += sizeof(struct async) + sizeof(struct urb) +
> > +          (as->usbm ? 0 : uurb->buffer_length) +
> >            num_sgs * sizeof(struct scatterlist);
>
> Are you sure?  Where is the buffer_length being added to the size here?
> What am I missing?
>
> thanks,
>
> greg k-h

  reply index

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-14 21:29 gavinli
2019-08-15 12:53 ` Greg KH
2019-08-16  5:51   ` Gavin Li [this message]
2019-08-15 19:16 ` Alan Stern

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