linux-kernel - Re: [PATCH v2] Introduce a version6 of autofs interface, to fix design error.

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Date:	Sun, 29 Apr 2012 11:45:21 +0400
From:	Michael Tokarev <mjt@....msk.ru>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Thomas Meyer <thomas@...3r.de>,
	David Miller <davem@...emloft.net>,
	linux-kernel@...r.kernel.org, autofs@...r.kernel.org,
	raven@...maw.net, stable@...nel.org
Subject: Re: [PATCH v2] Introduce a version6 of autofs interface, to fix design
 error.

[Hit "reply" instead of "Reply to all".. I'm sorry for a repost]

On 29.04.2012 11:19, Linus Torvalds wrote:
[]
>> /proc/1/fdinfo/16  -- the autofs pipe fd# -- shows flags=02004000
>> which is O_CLOEXEC|O_NONBLOCK, but this is the other end of the
>> pipe..  shouldn't the READ side of the pipe have O_DIRECT flag now?
>
> Gaah, it should, but it won't.
>
> I bet my original patch worked fine, because the pipe has only one
> inode and pipe structure. But it has *two* 'struct file's associated
> with it, and autofs only ever sees the writing side, and never gets to
> mark the reading side O_DIRECT. So yeah, the reading side won't do the
> proper packetized read.

Can't we go - in kernel - from one struct file to pipe structure to
another file structure and set O_DIRECT there?  Autofs kernel code
checks if the file descriptor is a pipe, so it should be possible...

Thanks,

/mjt
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