On Tue, Aug 12, 2008 at 04:26:10PM -0500, Archie Cobbs wrote:
> On Thu, Aug 7, 2008 at 1:26 PM, Archie Cobbs <archie@xxxxxxxxxxxx> wrote:
> > I have an application involving the loopback device where it would be
> > valuable for the underlying file to be opened with the O_DIRECT flag.
> >
> > Any thoughts one way or the other about adding support to losetup(8)
> > and mount(8) for a 'direct' option that would enable this?
> >
> > I will propose a patch if people think this would be a reasonable thing to do.
>
> Add support for opening loopback files with O_DIRECT.
[...]
> mode = (*options & SETLOOP_RDONLY) ? O_RDONLY : O_RDWR;
> + if (*options & SETLOOP_DIRECT)
> + mode |= O_DIRECT;
> if ((ffd = open(file, mode)) < 0) {
Do you remember http://lkml.org/lkml/2007/1/10/233 ?
.. use O_DIRECT for files is BAD idea (and loop device is nothing
other than a file on standard FS).
I'm really not sure if we want to support this feature. I'm also not
sure if kernel loop device code is ready for O_DIRECT. (BTW, O_DIRECT
reads and writes must be aligned, ...)
Sorry, but I have to see ACK/NACK from relevant kernel person.
Redirecting to lkml.
Karel
--
Karel Zak <kzak@xxxxxxxxxx>
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