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From: Al Viro <>
To: Mark Fasheh <>
	Andrew Morton <>,
	Amir Goldstein <>,, Jeff Mahoney <>,
Subject: Re: [PATCH 2/4] nfs: check for NULL vfsmount in nfs_getattr
Date: Thu, 2 Aug 2018 01:43:48 +0100	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Tue, Jul 31, 2018 at 10:51:57PM +0000, Mark Fasheh wrote:
> Hi Al,
> On Tue, Jul 31, 2018 at 11:16:05PM +0100, Al Viro wrote:
> > On Tue, Jul 31, 2018 at 02:10:43PM -0700, Mark Fasheh wrote:
> > > ->getattr from inside the kernel won't always have a vfsmount, check for
> > > this.
> > 
> > Really?  Where would that happen?
> It happens in my first patch. FWIW, I'm not tied to that particular bit of
> code, or even this (latest) approach. I would actually very much appreciate
> your input into how we might fix the problem we have where we are sometimes
> not exporting a correct ino/dev pair to user space.

Which callers would those be?  I don't see anything in your series that
wouldn't have vfsmount at hand...

> I have a good break-down of the problem and possible solutions here:

btrfs pulling odd crap with device numbers is a problem, but this is far from
the most obvious unpleasantness caused by that - e.g. userland code expecting
that unequal st_dev for directory and subdirectory means that we have
a mountpoint there.  Or assuming it can compare that to st_dev of mountpoints
(or, indeed, the values in /proc/self/mountinfo) to find which fs it's on...

/proc/*/maps is unfortunate, but it does contain the pathnames, doesn't it?
What _real_ problems are there - the ones where we don't have a saner solution?
Note that /proc/locks is (a) FPOS interface and (b) unsuitable for your
approach anyway.

  reply	other threads:[~2018-08-02  2:32 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-31 21:10 [RFC PATCH 0/4] vfs: map unique ino/dev pairs for user space Mark Fasheh
2018-07-31 21:10 ` [PATCH 1/4] vfs: introduce function to map unique ino/dev pairs Mark Fasheh
2018-07-31 23:21   ` Mark Fasheh
2018-08-01  5:41     ` Amir Goldstein
2018-08-01 15:59       ` Mark Fasheh
2018-07-31 21:10 ` [PATCH 2/4] nfs: check for NULL vfsmount in nfs_getattr Mark Fasheh
2018-07-31 22:16   ` Al Viro
2018-07-31 22:51     ` Mark Fasheh
2018-08-02  0:43       ` Al Viro [this message]
2018-08-03  2:04         ` Mark Fasheh
2018-07-31 21:10 ` [PATCH 3/4] proc: use vfs helper to get ino/dev pairs for maps file Mark Fasheh
2018-07-31 21:10 ` [PATCH 4/4] locks: map correct ino/dev pairs when exporting to userspace Mark Fasheh
2018-08-01  5:37   ` Amir Goldstein
2018-08-01 17:45     ` Mark Fasheh
2018-08-01 11:03   ` Jeff Layton
2018-08-01 20:38     ` Mark Fasheh
2018-08-02  0:24 ` [RFC PATCH 0/4] vfs: map unique ino/dev pairs for user space J. R. Okajima

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