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    SubjectRe: RFC: allow empty symlink targets
    On Wed 2013-05-15 23:03:35, Al Viro wrote:
    > On Wed, May 15, 2013 at 01:38:48PM +0100, P??draig Brady wrote:
    > > >> In today's Austin Group meeting, I was tasked to open a new bug that
    > > >> would state specifically how the empty symlink is resolved; the intent
    > > >> is to allow both Solaris behavior (current directory) and BSD behavior
    > > >> (ENOENT). Meanwhile, everyone was in agreement that the Linux kernel
    > > >> has a bug for rejecting the creation of an empty symlink, but once that
    > > >> bug is fixed, then Linux can choose either Solaris or BSD behavior for
    > > >> how to resolve such a symlink.
    >
    > Austin Group Is At It Again, Demands at 11...
    >
    > Would you mind explaining who's "everyone" and why would we possibly
    > want to honour that agreement of yours? Functionality in question is
    > utterly pointless, seeing that semantics of such symlinks is OS-dependent
    > anyway *and* that blanket refusal to traverse such beasts is a legitimate
    > option. What's the point in allowing to create them in the first
    > place?

    BSD may have created them. Or evil sysadmin (me) might have created
    them with hex editor.

    AFAICT we seem to have the Solaris behavior (current directory):

    pavel@amd:/mnt/foo$ ls -al link2/
    total 3
    drwxr-xr-x 2 pavel pavel 1024 May 26 11:34 .
    drwxr-xr-x 4 pavel pavel 1024 May 26 11:29 ..
    -rw-r--r-- 1 pavel pavel 5 May 26 11:29 file1
    lrwxrwxrwx 1 pavel pavel 5 May 26 11:29 link1 -> file1
    lrwxrwxrwx 1 pavel pavel 21 May 26 11:34 link2 ->
    lrwxrwxrwx 1 pavel pavel 5 May 26 11:29 this_will_be_null_link ->
    file1
    pavel@amd:/mnt/foo$ cd link2/
    pavel@amd:/mnt/foo/link2$ ls -al
    total 3
    drwxr-xr-x 2 pavel pavel 1024 May 26 11:34 .
    drwxr-xr-x 4 pavel pavel 1024 May 26 11:29 ..
    -rw-r--r-- 1 pavel pavel 5 May 26 11:29 file1
    lrwxrwxrwx 1 pavel pavel 5 May 26 11:29 link1 -> file1
    lrwxrwxrwx 1 pavel pavel 21 May 26 11:34 link2 ->
    lrwxrwxrwx 1 pavel pavel 5 May 26 11:29 this_will_be_null_link ->
    file1
    pavel@amd:/mnt/foo/link2$ cd link2/
    pavel@amd:/mnt/foo/link2/link2$ ls
    file1 link1 link2 this_will_be_null_link
    pavel@amd:/mnt/foo/link2/link2$ cd ..

    They are _not_ detected as broken during runtime (ext2 fs is not marked as
    containing errors) but fsck seems to handle them correctly.

    pavel@amd:~/misc$ /sbin/fsck.ext2 -f delme2.fs
    e2fsck 1.41.12 (17-May-2010)
    Pass 1: Checking inodes, blocks, and sizes
    Pass 2: Checking directory structure
    Symlink /foo/link2 (inode #7717) is invalid.
    Clear<y>? yes

    Pass 3: Checking directory connectivity
    Pass 4: Checking reference counts
    Pass 5: Checking group summary information

    delme2.fs: ***** FILE SYSTEM WAS MODIFIED *****
    delme2.fs: 15/25064 files (0.0% non-contiguous), 4724/100000 blocks
    pavel@amd:~/misc$

    I was looking for nice kernel crash but alas, nothing :-).
    Pavel
    --
    (english) http://www.livejournal.com/~pavelmachek
    (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html


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