[bug #25538] excluded files are still stat()ed

[Kevin Pulo]

URL:
  <http://savannah.gnu.org/bugs/?25538>

                 Summary: excluded files are still stat()ed
                 Project: GNU Core Utilities
            Submitted by: devkev
            Submitted on: Tue 10 Feb 2009 04:24:35 AM GMT
                Category: None
                Severity: 3 - Normal
              Item Group: None
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any

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Details:

My problem is that files I have excluded from du using -X or --exclude still
have stat() run on them.  In particular, this is a problem when trying to
exclude some fuse filesystems on Linux, eg. sshfs and encfs, which deny all
access to other users (including root).

For example:


address@hidden:~# du -axk /home/kev/mnt/sf     
du: cannot access `/home/kev/mnt/sf/home': Permission denied
4       /home/kev/mnt/sf
address@hidden:~# du -axk --exclude=/home/kev/mnt/sf/home /home/kev/mnt/sf
du: cannot access `/home/kev/mnt/sf/home': Permission denied
4       /home/kev/mnt/sf
address@hidden:~# echo $? 
1
address@hidden:~# 


The non-zero exit status is particularly troubling, since it means I cannot
chain other commands after du using '&&' whenever it's operating on a tree
that has these sorts of fuse fs's in it.

The only workaround at the moment is to exclude the parent directory, eg.
--exclude=~kev/mnt/sf in the example above.  This unfortunately means that
everything else in that directory is also excluded.


address@hidden:~# du -axk --exclude=/home/kev/mnt/sf /home/kev/mnt/sf
address@hidden:~# echo $?
0
address@hidden:~# 


Having looked at the code, I'm not sure how this would best be fixed.  The
list of excluded files is only used in process_file(), which is too late.  I
presume that the stat() is happening inside fts_read(), which populates
end->fts_statp with the results of the stat() call.  I suppose that extending
fts_read() to also respect the exclusion list would be fairly invasive. 
Alternatively, the EPERM could persist during the fts_read(), but then be
somehow "forgotten about" later for excluded files, allowing the exit status
to return to being 0 (assuming no other genuine errors).




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