lkml.org 
[lkml]   [2014]   [Nov]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 08/17] {macvtap,tun}_get_user(): switch to iov_iter
On Mon, Nov 24, 2014 at 12:27:42AM +0000, Ben Hutchings wrote:
> > copylen = vnet_hdr.hdr_len ? vnet_hdr.hdr_len : GOODCOPY_LEN;
> > if (copylen > good_linear)
> > copylen = good_linear;
> > linear = copylen;
> > - if (iov_pages(iv, vnet_hdr_len + copylen, count)
> > - <= MAX_SKB_FRAGS)
> > + i = *from;
> > + iov_iter_advance(&i, copylen);
> > + if (iov_iter_npages(&i, INT_MAX) <= MAX_SKB_FRAGS)
>
> The maxpages argument should be MAX_SKB_FRAGS + 1 as we don't need the
> exact number.

In principle, that's true, but... Do we really care? It only buys you
anything if you have a monstrously fragmented iovec. And if you end up
spending too considerable amount of time in that loop in iov_iter_npages,
you are by definition on the slow path - it *will* fail, since we do not
even try to merge adjacent iovec segments. Never had...


\
 
 \ /
  Last update: 2014-11-24 11:41    [W:0.081 / U:4.664 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site