linux-kernel - Re: [PATCH 1/4] fanotify: flush outstanding perm requests on group destroy

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Message-Id: <201008241136.30064.agruen@suse.de>
Date:	Tue, 24 Aug 2010 11:36:29 +0200
From:	Andreas Gruenbacher <agruen@...e.de>
To:	Tvrtko Ursulin <tvrtko.ursulin@...hos.com>
Cc:	Eric Paris <eparis@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/4] fanotify: flush outstanding perm requests on group destroy

On Tuesday 24 August 2010 10:49:45 Tvrtko Ursulin wrote:
> I think just switching to interruptible sleep in
> fanotify_get_response_from_access should be fine. And it should probably
> deny the current event when signal is received.

Well the result would be -EINTR from the system call that blocked on the
perm event, the same as with an interruptible nfs mount.  The process would 
never get -EPERM.  Processes may
not be prepared to handle -EINTR in all cases, and so it may make more sense
to use the same behavior as NFS and only allow SIGKILL to kill a process 
blocked on a perm event (which the blocked process will never see).

>From the nfs man page:
> intr / nointr
> 
> Selects whether to allow signals to interrupt file operations on this mount
> point.  If neither option is specified (or if nointr is specified),
> signals do not interrupt NFS file operations.  If intr is  specified, 
> system  calls return EINTR if an in-progress NFS operation is interrupted
> by a signal.
> 
> Using  the  intr option is preferred to using the soft option because it is
> significantly less likely to result in data corruption.  The intr / nointr
> mount option is deprecated  after  kernel  2.6.25.   Only SIGKILL  can 
> interrupt  a  pending  NFS operation on these kernels, and if specified,
> this mount option is ignored to provide backwards  compatibility with
> older kernels.

Andreas
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