union mount status

union mount status

[Daniel Lezcano]

Hi all,

What is the status of this patchset ?
Bharata Rao told me, no consensus was reached yet.
After looking at Jan Blunk's ftp server, it looks like the latest 
patchset was for 2.6.25-mm1. Is anyone working on this patchset right now ?

Thanks
   -- Daniel

Re: union mount status

[Jan Blunck]

On Wed, Oct 15, Daniel Lezcano wrote:

> Hi all,
> 
> What is the status of this patchset ?
> Bharata Rao told me, no consensus was reached yet.
> After looking at Jan Blunk's ftp server, it looks like the latest 
> patchset was for 2.6.25-mm1. Is anyone working on this patchset right now ?

Not that I know of.

The state is as follows: we (David Woodhouse, Bharata Rao, Erez Zadok and me)
agreed on a more or less final version of the whiteout patches. I haven't
posted them yet since I know that Al Viro isn't convinced of the idea that
they are actaully necessary. My plan was to solve the readdir() issues first,
because they are the biggest roadblock IMHO. Bharata worked on some glibc
readdir stuff but I don't know how that went.

Regards,
	Jan

-- 
Jan Blunck <jblunck@suse.de>

Re: union mount status

[Daniel Lezcano]

Jan Blunck wrote:
> On Wed, Oct 15, Daniel Lezcano wrote:
> 
>> Hi all,
>>
>> What is the status of this patchset ?
>> Bharata Rao told me, no consensus was reached yet.
>> After looking at Jan Blunk's ftp server, it looks like the latest 
>> patchset was for 2.6.25-mm1. Is anyone working on this patchset right now ?
> 
> Not that I know of.
> 
> The state is as follows: we (David Woodhouse, Bharata Rao, Erez Zadok and me)
> agreed on a more or less final version of the whiteout patches. I haven't
> posted them yet since I know that Al Viro isn't convinced of the idea that
> they are actaully necessary. 

The union mount could *very* interesting for the containers (aka 
namespaces). If you create a container, you can share the same rootfs 
between  the different containers and make a COW for each container 
writing on its own filesystem, no ? Using together the mount namespaces, 
the union mount and the ro bind mount, can be very powerful IMHO.

Re: union mount status

[Ian Kent]

On Wed, 15 Oct 2008, Jan Blunck wrote:

> On Wed, Oct 15, Daniel Lezcano wrote:
> 
> > Hi all,
> > 
> > What is the status of this patchset ?
> > Bharata Rao told me, no consensus was reached yet.
> > After looking at Jan Blunk's ftp server, it looks like the latest 
> > patchset was for 2.6.25-mm1. Is anyone working on this patchset right now ?
> 
> Not that I know of.
> 
> The state is as follows: we (David Woodhouse, Bharata Rao, Erez Zadok and me)
> agreed on a more or less final version of the whiteout patches. I haven't
> posted them yet since I know that Al Viro isn't convinced of the idea that
> they are actaully necessary. My plan was to solve the readdir() issues first,
> because they are the biggest roadblock IMHO. Bharata worked on some glibc
> readdir stuff but I don't know how that went.

I'm trying to work through applying your patches to a current kernel so I 
can have a decent look through them.
Do you have a more recent version of the patches?

What are your current thoughts on the readdir() problem?

Ian

Re: union mount status

[Ian Kent]

On Fri, 21 Nov 2008, Ian Kent wrote:

> On Wed, 15 Oct 2008, Jan Blunck wrote:
> 
> > On Wed, Oct 15, Daniel Lezcano wrote:
> > 
> > > Hi all,
> > > 
> > > What is the status of this patchset ?
> > > Bharata Rao told me, no consensus was reached yet.
> > > After looking at Jan Blunk's ftp server, it looks like the latest 
> > > patchset was for 2.6.25-mm1. Is anyone working on this patchset right now ?
> > 
> > Not that I know of.
> > 
> > The state is as follows: we (David Woodhouse, Bharata Rao, Erez Zadok and me)
> > agreed on a more or less final version of the whiteout patches. I haven't
> > posted them yet since I know that Al Viro isn't convinced of the idea that
> > they are actaully necessary. My plan was to solve the readdir() issues first,
> > because they are the biggest roadblock IMHO. Bharata worked on some glibc
> > readdir stuff but I don't know how that went.
> 
> I'm trying to work through applying your patches to a current kernel so I 
> can have a decent look through them.

OK, I've applied your patch series from 2.6.23-mm1-2007-11-16 to the
linux-2.6 tree. I expect there are some mistakes due to the struct path 
changes that have gone on since these were done.

Are you willing to have a look through them to check they are as 
you expect.

I had a problem with union-mount-access.diff as you can see below, any 
suggestions about how to get around this?:

Subject: union-mount: don't report EROFS for union mounts

From: Ian Kent <raven@themaw.net>
** Mmmm .. I'll need to change these, but what to !! **

SuS v2 requires we report a read only fs too. For union-mounts this is a very
expensive check. So I'm lazy and just disable the check if we are on a lower
layer of an union.

Signed-off-by: Jan Blunck <jblunck@suse.de>
---

 fs/open.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)


diff --git a/fs/open.c b/fs/open.c
index 715266d..6f357e3 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -488,6 +488,9 @@ asmlinkage long sys_faccessat(int dfd, const char __user *filename, int mode)
 	 * inherently racy and know that the fs may change
 	 * state before we even see this result.
 	 */
+	/* OOPS: no struct nameidata anymore
+	 if (!(nd.um_flags & LAST_LOWLEVEL) && __mnt_is_readonly(nd.path.mnt))
+	 */
 	if (__mnt_is_readonly(path.mnt))
 		res = -EROFS;