From: Jens Axboe <axboe@kernel•dk>
To: Eric Dumazet <eric.dumazet@gmail•com>
Cc: linux-kernel <linux-kernel@vger•kernel.org>,
David Miller <davem@davemloft•net>,
netdev <netdev@vger•kernel.org>,
Tom Herbert <therbert@google•com>,
Al Viro <viro@zeniv•linux.org.uk>,
Hugh Dickins <hughd@google•com>, Changli Gao <xiaosuo@gmail•com>,
Andrew Morton <akpm@linux-foundation•org>,
Miklos Szeredi <mszeredi@suse•cz>
Subject: Re: [PATCH] vmsplice: relax alignement requirements for SPLICE_F_GIFT
Date: Fri, 20 Apr 2012 10:19:54 +0200 [thread overview]
Message-ID: <20120420081953.GJ7505@kernel.dk> (raw)
In-Reply-To: <1333530531.18626.550.camel@edumazet-glaptop>
On Wed, Apr 04 2012, Eric Dumazet wrote:
> It seems there is no fundamental reason to limit vmsplice()
> SPLICE_F_GIFT to page aligned chunks.
>
> All helpers are prepared to cope with offsets in page.
>
> This limitation makes vmsplice() API very impractical in the zero-copy
> land.
Sorry for the slow reply on this one. It's been a long time since I
wrote that code... If I recall correctly, the reason it currently
requires alignment, is that a gifted page is no longer yours, by
definition. So the alignment check was to ensure that we gift full
pages. But if the caller screws that up, I guess it's the callers
problem and it's a shame to limit the API in this way.
I will apply it for 3.5.
--
Jens Axboe
next prev parent reply other threads:[~2012-04-20 8:19 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-04 9:08 [PATCH] vmsplice: relax alignement requirements for SPLICE_F_GIFT Eric Dumazet
2012-04-20 8:19 ` Jens Axboe [this message]
2012-04-20 8:35 ` Eric Dumazet
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