Re: [fuse-devel] [PATCH] fuse: return -EAGAIN if the connection has not been init'ed

[Josef B. <jo...@re...>]

On Fri, Nov 13, 2009 at 02:55:24PM +0100, Miklos Szeredi wrote:
> On Fri, 13 Nov 2009, Eric Paris wrote:
> > mount         S ffff88001f86bd28     0  4126   4120 0x00000080
> > mount         S ffff88001f86bd28     0  4126   4120 0x00000080
> > ffff88001f86bc38 0000000000000086 0000000000000011 ffff88001f86bc08
> > 0000000000000700 0000000000000000 0000000000000013 ffffffff815884cd
> > ffff8800377532c8 000000000000f8e0 ffff8800377532c8 0000000000015600
> > Call Trace:
> > [<ffffffffa01bec71>] fuse_get_req+0xb8/0x15b [fuse]
> > [<ffffffffa01bf359>] fuse_getxattr+0x58/0x14f [fuse]
> > [<ffffffff811b9ea2>] get_vfs_caps_from_disk+0x52/0xcd
> > [<ffffffff81093809>] audit_copy_inode+0x83/0xb1
> > [<ffffffff81093d4f>] __audit_inode+0x1ee/0x1fd
> > [<ffffffff81104789>] audit_inode+0x28/0x2a
> > [<ffffffff811066b4>] do_path_lookup+0x63/0x8b
> > [<ffffffff81107c9c>] user_path_at+0x56/0x93
> > [<ffffffff810ffaf0>] sys_readlinkat+0x2d/0x91
> > [<ffffffff810ffb6f>] sys_readlink+0x1b/0x1d
> > [<ffffffff81011cf2>] system_call_fastpath+0x16/0x1b
> > 
> > Userspace called readlink() and the audit system (after the vfs worked
> > out the path) needs to collect any fcaps.
> 
> OK, this is a different problem than what I thought.  Agreed, audit is
> not doing anything wrong here.
> 
> The cause seems to be that fuse calls "mount -i -f ..." to add the
> filesystem entry to /etc/mtab.  mount(8) then goes off and tries to
> canonicalize the path, calling readlink() on the mountpoint.  Which is
> unnecessary, really.  The path has already been canonicalized, but
> unfortunately there's no way currently to tell this to mount.
> 
> In this light, the patch by Josef might be OK as a workaround, but
> I'll look at better ways to fix this.
> 
> Josef, can you check whether the mtab is still correctly updated with
> your patch?
> 

Yes mtab is correctly updated with my patch.  Like I said I'm open to other
options, this just happened to fix it and I figured I'd send it along to help
illustrate the problem hoping you had a better idea :).  Thanks,

Josef