Re: [PATCH] Add getdents32t syscall

[Andreas Dilger <adilger@clusterfs.com>]

On Thu, 26 Feb 2004, Jakub Jelinek wrote:
> Userland struct dirent is:
> (since 1997 or so), so with the extended getdents syscall glibc would need
> to memmove every name by 1 byte.

Actually, before you go through contortions trying to return this stuff to
user space, you should fix the GNU tools to use the information properly.

For example, rm stats the file each time before trying to unlink it even
if it has the file type information from getdents64().  It also tries to
do silly things like unlink() on a directory instead of rmdir, even after
the stat (RH9 coreutils 4.5.3-19 and 2.4.24):

    $ mkdir /tmp/foo
    $ touch /tmp/foo/f{1,2,3,4,5}
    $ strace rm -r /tmp/foo
    :
    :
    lstat64("/tmp/foo", {st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0
    access("/tmp/foo", W_OK)                 = 0
    unlink("/tmp/foo")                       = -1 EISDIR (Is a directory)

Um, hello - we just saw that it was a directory so why not try rmdir()?
It does the same thing when the directory is empty too.

    open(".", O_RDONLY|O_LARGEFILE|O_DIRECTORY) = 3
    lstat64("/tmp/foo", {st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0
    chdir("/tmp/foo")                        = 0
    lstat64(".", {st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0
    open(".", O_RDONLY|O_NONBLOCK|O_LARGEFILE|O_DIRECTORY) = 4
    fstat64(4, {st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0
    fcntl64(4, F_SETFD, FD_CLOEXEC)         = 0

    getdents64(4, /* 7 entries */, 4096)    = 168
    lstat64("f1", {st_mode=S_IFREG|0664, st_size=0, ...}) = 0
    access("f1", W_OK)                      = 0
    unlink("f1")                            = 0
    lstat64("f2", {st_mode=S_IFREG|0664, st_size=0, ...}) = 0
    access("f2", W_OK)                      = 0
    unlink("f2")                            = 0
    :
    :

So, for each file, we just got the file type info from getdents64(),
we still stat the file (not sure why), we check the permissions even
though we just statted it (could check perms from stat info or just
try to unlink and handle the error return code), and finally an unlink.

    getdents64(4, /* 0 entries */, 4096)    = 0
    close(4)                                = 0
    fchdir(3)                               = 0
    lstat64(".", {st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0
    lstat64("/tmp/foo", {st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0
    access("/tmp/foo", W_OK)                 = 0
    rmdir("/tmp/foo")                        = 0

Cheers, Andreas
--
Andreas Dilger
http://sourceforge.net/projects/ext2resize/
http://www-mddsp.enel.ucalgary.ca/People/adilger/