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From: Miklos Szeredi <miklos@szeredi.hu>
To: jens.axboe@oracle.com
Cc: miklos@szeredi.hu, akpm@linux-foundation.org, max@duempel.org,
	torvalds@linux-foundation.org, linux-fsdevel@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [patch 2/3] splice: implement default splice_read method
Date: Thu, 14 May 2009 19:54:33 +0200	[thread overview]
Message-ID: <E1M4f8b-0000Tb-GI@pomaz-ex.szeredi.hu> (raw)
In-Reply-To: <20090514172935.GR4140@kernel.dk> (message from Jens Axboe on Thu, 14 May 2009 19:29:35 +0200)

On Thu, 14 May 2009, Jens Axboe wrote:

> > The bigger problem is that the default_file_splice_write()
> > implementation in the other patch does the same (it calls
> > buf->ops->map() on all buffers).
> 
> Yep that's even worse, as that should go BUG() pretty much immediately
> when the KM_USER0 slot is reused!

No, ->map() calls plain kmap() if "atomic" argument is zero.
Nevertheless the deadlock due to multiple kmaps is still possible.

> > Hmm.  Simple solution would be to do a write() for each buffer.  But
> > this only affects HIGHMEM kernels, so it's a bit pointless to do that
> > on all archs.  Sigh...
> 
> It is unfortunate, we are going to be stuck with that for some time
> still...

I'm going to be offline till next monday, I'll post a fix after that.

Thanks,
Miklos

  reply	other threads:[~2009-05-14 17:55 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-05-07 13:37 [patch 0/3] make splice more generic Miklos Szeredi
2009-05-07 13:37 ` [patch 1/3] splice: implement pipe to pipe splicing Miklos Szeredi
2009-05-07 13:37 ` [patch 2/3] splice: implement default splice_read method Miklos Szeredi
2009-05-13  5:35   ` Andrew Morton
2009-05-13  6:37     ` Jens Axboe
2009-05-13  9:01       ` Miklos Szeredi
2009-05-14 17:29         ` Jens Axboe
2009-05-14 17:54           ` Miklos Szeredi [this message]
2009-05-14 18:00             ` Jens Axboe
2009-05-18 12:36               ` Miklos Szeredi
2009-05-19  9:38                 ` Jens Axboe
2009-05-07 13:37 ` [patch 3/3] splice: implement default splice_write method Miklos Szeredi
2009-05-07 15:55 ` [patch 0/3] make splice more generic Linus Torvalds
2009-05-11 15:17   ` Miklos Szeredi
2009-05-09 11:36 ` Max Kellermann
2009-05-11 12:12 ` Jens Axboe
2009-05-11 15:22   ` Miklos Szeredi
2009-05-14 20:27   ` Jamie Lokier
2009-05-15  7:32     ` Jens Axboe

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