From: Robert Hancock <hancockr@shaw.ca>
To: linux-kernel@vger.kernel.org
Cc: linux-man@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Subject: Re: open(2) says O_DIRECT works on 512 byte boundries?
Date: Wed, 28 Jan 2009 18:41:49 -0600 [thread overview]
Message-ID: <4980FB4D.9090009@shaw.ca> (raw)
In-Reply-To: <20090128213322.GA15789@kroah.com>
Greg KH wrote:
> In looking at open(2), it says that O_DIRECT works on 512 byte boundries
> with the 2.6 kernel release:
> Under Linux 2.4, transfer sizes, and the alignment of the user
> buffer and the file offset must all be multiples of the logical
> block size of the file system. Under Linux 2.6, alignment to
> 512-byte boundaries suffices.
>
> However if you try to access an O_DIRECT opened file with a buffer that
> is PAGE_SIZE aligned + 512 bytes, it fails in a bad way (wrong data is
> read.)
>
> Is this just a mistake in the documentation? Or am I reading it
> incorrectly?
>
> I have a test program that shows this if anyone wants it.
Well, it sounds like a bug to me.. even if it's not supported, if you do
such an access, surely the kernel should detect that and return EINVAL
or something rather than reading corrupted data..
next prev parent reply other threads:[~2009-01-29 0:42 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-01-28 21:33 open(2) says O_DIRECT works on 512 byte boundries? Greg KH
2009-01-29 0:41 ` Robert Hancock [this message]
[not found] ` <20090129011758.GA26534@kroah.com>
2009-01-29 2:59 ` Michael Kerrisk
2009-01-29 3:13 ` Greg KH
2009-01-29 15:40 ` Jeff Moyer
2009-01-30 6:16 ` Greg KH
2009-01-29 5:13 ` KAMEZAWA Hiroyuki
2009-01-29 7:10 ` KOSAKI Motohiro
2009-01-30 6:17 ` Greg KH
2009-02-02 22:08 ` Andrea Arcangeli
2009-02-03 1:29 ` KAMEZAWA Hiroyuki
2009-02-03 2:31 ` Andrea Arcangeli
2009-02-03 2:55 ` KAMEZAWA Hiroyuki
2009-02-03 3:42 ` KAMEZAWA Hiroyuki
2009-02-06 17:55 ` Andrea Arcangeli
2009-02-03 3:50 ` Greg KH
2009-02-03 15:01 ` Andrea Arcangeli
2009-02-03 4:13 ` KAMEZAWA Hiroyuki
2009-02-03 4:38 ` KAMEZAWA Hiroyuki
2009-02-03 15:08 ` Andrea Arcangeli
2009-02-04 23:41 ` Greg KH
2009-02-06 17:54 ` Andrea Arcangeli
2009-02-06 18:38 ` Andrea Arcangeli
2009-02-07 13:32 ` Izik Eidus
2009-02-07 15:33 ` Andrea Arcangeli
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