linux-kernel - Re: [PATCH RFC] vfs: make fstatat retry on ESTALE errors from getattr call

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Message-ID: <87k41eo2m3.fsf@tucsk.pomaz.szeredi.hu>
Date:	Tue, 17 Apr 2012 16:27:16 +0200
From:	Miklos Szeredi <miklos@...redi.hu>
To:	Steve Dickson <SteveD@...hat.com>
Cc:	Jeff Layton <jlayton@...hat.com>,
	"Myklebust\, Trond" <Trond.Myklebust@...app.com>,
	Bernd Schubert <bernd.schubert@...m.fraunhofer.de>,
	Malahal Naineni <malahal@...ibm.com>,
	"linux-nfs\@vger.kernel.org" <linux-nfs@...r.kernel.org>,
	"linux-fsdevel\@vger.kernel.org" <linux-fsdevel@...r.kernel.org>,
	"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
	"pstaubach\@exagrid.com" <pstaubach@...grid.com>,
	"viro\@ZenIV.linux.org.uk" <viro@...IV.linux.org.uk>,
	"hch\@infradead.org" <hch@...radead.org>,
	"michael.brantley\@deshaw.com" <michael.brantley@...haw.com>,
	"sven.breuner\@itwm.fraunhofer.de" <sven.breuner@...m.fraunhofer.de>
Subject: Re: [PATCH RFC] vfs: make fstatat retry on ESTALE errors from getattr call

Steve Dickson <SteveD@...hat.com> writes:

> True, but even so... Giving file systems an opt-out option with the 
> default being out, maybe still have some merit... Making file systems
> enable this new type of functionality would cut down on any of the
> "surprise" that might occur with this redo ;-) 

I've been arguing for something slightly different for quite some time:
I never liked errno values which have side effects in the kernel yet
might be visible to userspace.

So why not introduce ERETRYSTALE, a *kernel internal* errno value that
userspace will never see and filesystems never accidentally set.  The
VFS can turn this into ESTALE if it doesn't retry for some reason
(e.g. already retried).

Thanks,
Miklos
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