[lxc-devel] [PATCH 1/1] lxc-start-ephemeral: handle the overlayfs workdir option (v2)

[KATOH Yasufumi]

Hi,

I tested on kernel 3.18.1 with your patch. It works fine, but there is
one problem.

>>> On Tue, 13 Jan 2015 00:08:37 +0000
    in message   "[lxc-devel] [PATCH 1/1] lxc-start-ephemeral: handle the overlayfs workdir option (v2)"
                  Serge Hallyn-san wrote:

> We fixed this some time ago for basic lxc-start, but never did
> lxc-start-ephemeral.

> Since the lxc-start patches were pushed, Miklos has given us a
> way to detect whether we need the workdir= option.  So the
> bdev.c code could be simplified to check for "overlay\n" in
> /proc/filesystems just as lxc-start-ephemeral does.  This
> patch doesn't do that.



> Changelog (v2):
> 	1. use 'overlay' fstype for new overlay upstream module
> 	2. avoid using unneeded readlines().

> Signed-off-by: Serge Hallyn <serge.hallyn at ubuntu.com>
> ---
>  src/lxc/lxc-start-ephemeral.in | 25 ++++++++++++++++++++++++-
>  1 file changed, 24 insertions(+), 1 deletion(-)

> diff --git a/src/lxc/lxc-start-ephemeral.in b/src/lxc/lxc-start-ephemeral.in
> index c999e74..36e2579 100644
> --- a/src/lxc/lxc-start-ephemeral.in
> +++ b/src/lxc/lxc-start-ephemeral.in
> @@ -219,6 +219,14 @@ for entry in args.cdir:
>          dst_path = "%s/rootfs/%s" % (dest_path, src_path)
>          overlay_dirs += [(src_path, dst_path)]
 
> +# do we have the new overlay fs which requires workdir, or the older
> +# overlayfs which does not?
> +have_new_overlay = False
> +with open("/proc/filesystems", "r") as fd:
> +    for line in fd:
> +        if line == "nodev\toverlay\n":
> +            have_new_overlay = True

When the overlayfs is module, and the module is not loaded at this
moment, "have_new_overlay" is False and the mount will fail.

We need to load the overlayfs module before the check.

> +
>  # Generate pre-mount script
>  with open(os.path.join(dest_path, "pre-mount"), "w+") as fd:
>      os.fchmod(fd.fileno(), 0o755)
> @@ -231,16 +239,31 @@ LXC_NAME="%s"
>      count = 0
>      for entry in overlay_dirs:
>          target = "%s/delta%s" % (dest_path, count)
> +        workdir = "%s/work%s" % (dest_path, count)
>          fd.write("mkdir -p %s %s\n" % (target, entry[1]))
> +        if have_new_overlay:
> +            fd.write("mkdir -p %s\n" % workdir)
 
>          if args.storage_type == "tmpfs":
>              fd.write("mount -n -t tmpfs -o mode=0755 none %s\n" % (target))
> +            if have_new_overlay:
> +                fd.write("mount -n -t tmpfs -o mode=0755 none %s\n" % (workdir))
 
>          fd.write("getfacl -a %s | setfacl --set-file=- %s || true\n" % (entry[0], target))
>          fd.write("getfacl -a %s | setfacl --set-file=- %s || true\n" % (entry[0], entry[1]))
> +        if have_new_overlay:
> +            fd.write("getfacl -a %s | setfacl --set-file=- %s || true\n" % (entry[0], workdir))
 
>          if args.union_type == "overlayfs":
> -            fd.write("mount -n -t overlayfs"
> +            if have_new_overlay:
> +                fd.write("mount -n -t overlay"
> +                     " -oupperdir=%s,lowerdir=%s,workdir=%s none %s\n" % (
> +                         target,
> +                         entry[0],
> +                         workdir,
> +                         entry[1]))
> +            else:
> +                fd.write("mount -n -t overlayfs"
>                       " -oupperdir=%s,lowerdir=%s none %s\n" % (
>                           target,
>                           entry[0],
> -- 
> 2.1.0

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