From: Theodore Ts'o <tytso@mit.edu>
To: Dave Chinner <david@fromorbit.com>
Cc: Christoph Hellwig <hch@infradead.org>,
torvalds@linux-foundation.org,
Dmitry Monakhov <dmonlist@gmail.com>,
Ext4 Developers List <linux-ext4@vger.kernel.org>,
linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org
Subject: Re: O_DIRECT as a hint, was: Re: [PATCH] ext4: refuse O_DIRECT opens for mode where DIO doesn't work
Date: Tue, 26 Apr 2016 23:25:26 -0400 [thread overview]
Message-ID: <20160427032526.GC30021@thunk.org> (raw)
In-Reply-To: <20160427022746.GJ18496@dastard>
On Wed, Apr 27, 2016 at 12:27:46PM +1000, Dave Chinner wrote:
> > At this point I wonder if we should simply treat O_DIRECT as a hint
> > and always allow it, and just let the file system optimize for it
> > (skip buffering, require alignment, relaxed Posix atomicy requirements)
> > if it is set.
>
> I thought that's how most filesystems treated it, anyway. i.e.
> anything they can't do via direct IO, they fell back to buffered IO
> to complete (e.g. for allocation or append writes, etc). Hence why I
> suggested the fallback rather than erroring out....
No, some file systems return EINVAL on the open. In fact that's what
the _require_odirect test in xfstests relies upon....
- Ted
next prev parent reply other threads:[~2016-04-27 3:25 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-24 4:27 [PATCH] ext4: refuse O_DIRECT opens for mode where DIO doesn't work Theodore Ts'o
2016-04-25 9:35 ` Dmitry Monakhov
2016-04-25 23:49 ` Dave Chinner
2016-04-26 0:20 ` Theodore Ts'o
2016-04-26 8:14 ` O_DIRECT as a hint, was: " Christoph Hellwig
2016-04-26 15:07 ` Mike Marshall
[not found] ` <20160426081451.GA25616-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
2016-04-27 2:16 ` Theodore Ts'o
2016-04-27 2:16 ` Theodore Ts'o
[not found] ` <20160427021649.GA30021-AKGzg7BKzIDYtjvyW6yDsg@public.gmane.org>
2016-04-27 2:22 ` Eric Sandeen
2016-04-27 2:22 ` Eric Sandeen
2016-04-27 2:25 ` Dave Chinner
2016-04-27 2:27 ` Dave Chinner
2016-04-27 2:27 ` Dave Chinner
2016-04-27 3:25 ` Theodore Ts'o [this message]
[not found] ` <20160427032526.GC30021-AKGzg7BKzIDYtjvyW6yDsg@public.gmane.org>
2016-04-27 3:37 ` Dave Chinner
2016-04-27 3:37 ` Dave Chinner
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