[elbe-devel] [PATCH 1/2] Add files protection from ChRootFilesystem's excursion.

[Bastian Germann]

> From: Olivier Dion <dion at linutronix.de>
> 
> If we modify one of the excursion's files, this modification won't be
> commited since after exiting the context manager of the filesystem,
> the excursion is undo.

undone

> 
> Thus, the method ChRootFilsystem.protect takes a list of files to

ChRootFilesystem

> protect from the excursion and return the filesytem object.  This can

returns the filesystem

> be use in conjonction with the 'with' statement, allowing modification

used in conjunction

> of the protected files.
> 
> * Example
> 
>   Here the user wants to link "/etc/resolv.conf" to a target.  But
>   "/etc/resolv.conf" is usually restored by the excursion.
> 
>   Using the new 'protect' method, we can bypass the excursion.
> 
>   ``````````````````````````````````````````````````````````````````````
>   my_file = "/etc/resolv.conf"
>   with rfs.protect({my_file}):
>      link(my_file, to_some_target)
>   ``````````````````````````````````````````````````````````````````````
> 
> Signed-off-by: Olivier Dion <dion at linutronix.de>

With these changes applied
Reviewed-by: Bastian Germann <bage at linutronix.de>

> ---
>  elbepack/efilesystem.py | 29 ++++++++++++++++++++++-------
>  1 file changed, 22 insertions(+), 7 deletions(-)
> 
> diff --git a/elbepack/efilesystem.py b/elbepack/efilesystem.py
> index 8d766e3c..abfb239b 100644
> --- a/elbepack/efilesystem.py
> +++ b/elbepack/efilesystem.py
> @@ -191,7 +191,10 @@ class Excursion(object):
>      def end(cls, rfs):
>          r = cls.RFS[rfs.path]
>          for tmp in r:
> -            tmp._undo_excursion(rfs)
> +            if tmp.origin not in rfs.protect_from_excursion:
> +                tmp._undo_excursion(rfs)
> +            else:
> +                tmp._del_rfs_file(tmp._saved_to(), rfs)
>          del r
>  
>      def __init__(self, path, restore, dst):
> @@ -199,10 +202,12 @@ class Excursion(object):
>          self.restore = restore
>          self.dst = dst
>  
> +    def _saved_to(self):
> +        return "%s.orig" % self.origin
>  
>      def _do_excursion(self, rfs):
>          if rfs.lexists(self.origin) and self.restore is True:
> -            save_to = "%s.orig" % self.origin
> +            save_to = self._saved_to()
>              system('mv %s %s' % (rfs.fname(self.origin), rfs.fname(save_to)))
>          if os.path.exists(self.origin):
>              if self.dst is not None:
> @@ -211,13 +216,17 @@ class Excursion(object):
>                  dst = self.origin
>              system('cp %s %s' % (self.origin, rfs.fname(dst)))
>  
> -    def _undo_excursion(self, rfs):
> -        saved_to = "%s.orig" % self.origin
> -        if rfs.lexists(self.origin):
> +    # This should be a method of rfs
> +    def _del_rfs_file(self, filename, rfs):
> +        if rfs.lexists(filename):
>              flags = "-f"
> -            if rfs.isdir(self.origin):
> +            if rfs.isdir(filename):
>                  flags += "r"
> -            system('rm %s %s' % (flags, rfs.fname(self.origin)))
> +            system("rm %s %s" % (flags, rfs.fname(filename)))
> +
> +    def _undo_excursion(self, rfs):
> +        saved_to = self._saved_to()
> +        self._del_rfs_file(self.origin, rfs)
>          if self.restore is True and rfs.lexists(saved_to):
>              system('mv %s %s' % (rfs.fname(saved_to), rfs.fname(self.origin)))
>  
> @@ -229,6 +238,7 @@ class ChRootFilesystem(ElbeFilesystem):
>          self.interpreter = interpreter
>          self.cwd = os.open("/", os.O_RDONLY)
>          self.inchroot = False
> +        self.protect_from_excursion = set()
>  
>      def __del__(self):
>          os.close(self.cwd)
> @@ -264,6 +274,11 @@ class ChRootFilesystem(ElbeFilesystem):
>          self.umount()
>  
>          Excursion.end(self)
> +        self.protect_from_excursion = set()
> +
> +    def protect(self, files):
> +        self.protect_from_excursion = files
> +        return self
>  
>      def mount(self):
>          if self.path == '/':
>