Re: [Xen-devel] [PATCH] libxl: introduce an option for disabling the non-O_DIRECT workaround [and 1 more messages]

[George Dunlap <george.dunlap@xxxxxxxxxxxxx>]

On 11/28/2013 11:38 AM, Ian Jackson wrote:
> George Dunlap writes ("Re: [Xen-devel] [PATCH] libxl: introduce an option for 
> disabling the non-O_DIRECT workaround"):
> > Not everyone builds her own kernel from the latest release; until we can
> > be relatively sure that this fix has hit distros (including older
> > LTS-style ones), we have to deal with the fact that the O_DIRECT bug may
> > be present.  The purpose of this flag is to enable you to turn it on
> > when you know it's safe -- for instance, if you're running a kernel with
> > this changeset.
> >
> > It is worth asking the question now though: Given that this has been
> > checked in, would it make sense to switch the polarity of this --
> > default to O_DIRECT on and have a flag to allow people to switch it off?
> Surely if the kernel has been fixed, libxl should detect this and turn
> off the workaround automatically.   The kernel should expose something
> that lets us tell.  (If nothing else, we can use the version number,
> although that's really not ideal.)
Given how many bugs there are in the Linux kernel, it would seem rather 
unweildy to have a robust way of specifying if any individual one had 
been fixed for any given bug...
 -George

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