Re: Bug#369822: ls -i stats unnecessarily

[Jim Meyering]

I wrote:
> Thanks for the report.
>
> You're right that in some cases ls could be optimized to avoid the
> lstat calls.  However deciding when to do it is not easy.
> It is possible
>   - when dirent.d_ino is available (this is easy), and
>   - when dirent.d_ino is guaranteed to be valid (this is tricky)
>
> The latter is harder because for some files (mount points in a chroot
> with a buggy glibc) d_ino is nonzero and wrong.  In those cases, you have
> to use lstat to get the true value.  The invalid d_ino problem came up
> recently with the report of pwd failing on systems with a losing (and
> slightly old) glibc.
>
> If someone else does all the work to make ensure the optimization
> is safe, I'd accept a patch.

After writing that, I remembered that this optimization
has already been done on the trunk.  However, there's no check
for the glibc problem:

2006-02-25  Eric Blake  <address@hidden>

        In ls, avoid calling stat for --inode (-i), when possible.
        * src/pwd.c (NOT_AN_INODE_NUMBER, D_INO): Move to ...
        * src/system.h: ... here, for use in ...
        * src/ls.c (main): ... here.  Prefer dirent.d_ino to stat when
        possible.
        (gobble_file): Add inode argument.
        (print_dir): Pass inode if available.
        (usage): Remove inaccuracy.

The problem is rare enough that I won't be losing any
sleep over it.  But it would be good to fix it, or at least
add a test case comparing st_ino vs. d_ino for every readable
directory from "." up to "/".  Then (from test failure reports)
we can hope to get an idea of how often the problem arises.