[CRIU] [PATCH 6/7] inotify: Use ghost files if the watchee is a deleted file

[Pavel Emelyanov]

On 12/03/2012 07:27 PM, Cyrill Gorcunov wrote:
> 
> The watch target might be a deleted file. In this case we can't
> re-create it on restore procedure.
> 
> A typical scenario
> ------------------
> 
>  fd = inotify_init1()
>  wd = open(path)
>  inotify_add_watch(path)
>  unlink(path)
>  ... checkpoint ...
> 
> here we have a @path which is unlinked but still present in inotify
> watch list because inode is not yet freed. And if the program is killed
> after checkpoint the last reference to a path get eliminated and inode
> get freed from the kernel memory.
> 
> Thus any furher attempts to open the path via file handle (note that file
> handle can't be used to create new file, the kernel doesn't permit that)
> will simply fail.
> 
> So if plain opening via file handle failed we assume that at least
> the file might be in our ghost files list (we're optimists, right?)
> and if we successed we simply use a path generated by ghost file
> engine for us.
> 
> Signed-off-by: Cyrill Gorcunov <gorcunov at openvz.org>
> ---
>  inotify.c | 21 +++++++++++++++------
>  1 file changed, 15 insertions(+), 6 deletions(-)
> 


> +		gf = lookup_ghost_file_st(kdev_to_odev(iwe->s_dev), iwe->i_ino);

Why kdev_to_odev? The device should be in one format on both sides.