On Tue, 2025-01-28 at 03:07 +0000, Al Viro wrote:
> On Mon, Jan 27, 2025 at 05:10:23PM -0800, Viacheslav Dubeyko wrote:
> > From: Viacheslav Dubeyko <Slava.Dubeyko@xxxxxxx>
> >
> > This patch introduces CEPH_HIDDEN_DIR_NAME. It
> > declares name of the hidden directory .ceph in
> > the include/linux/ceph/ceph_fs.h instead of hiding
> > it in dir.c file. Also hardcoded length of the name
> > is changed on strlen(CEPH_HIDDEN_DIR_NAME).
>
> Hmm...
>
> Speaking of that area
> * how the hell could ceph_lookup() ever be called with dentry
> that is *NOT* negative? VFS certainly won't do that; I'm not sure about
> ceph_handle_notrace_create(), but it doesn't look like that's possible
> without server being malicious (if it's possible at all).
>
> * speaking of malicious servers, what happens if
> it gets CEPH_MDS_OP_LOOKUP and it returns a normal reply to positive
> lookup, but with cpu_to_le32(-ENOENT) shoved into head->result?
> AFAICS, ceph_handle_snapdir() will be called with dentry
> that is already made positive; results will not be pretty...
I assume that you imply this code:
/* can we conclude ENOENT locally? */
if (d_really_is_negative(dentry)) {
struct ceph_inode_info *ci = ceph_inode(dir);
struct ceph_dentry_info *di = ceph_dentry(dentry);
spin_lock(&ci->i_ceph_lock);
doutc(cl, " dir %llx.%llx flags are 0x%lx\n",
ceph_vinop(dir), ci->i_ceph_flags);
if (strncmp(dentry->d_name.name,
fsc->mount_options->snapdir_name,
dentry->d_name.len) &&
!is_root_ceph_dentry(dir, dentry) &&
ceph_test_mount_opt(fsc, DCACHE) &&
__ceph_dir_is_complete(ci) &&
__ceph_caps_issued_mask_metric(ci, CEPH_CAP_FILE_SHARED,
1)) {
__ceph_touch_fmode(ci, mdsc, CEPH_FILE_MODE_RD);
spin_unlock(&ci->i_ceph_lock);
doutc(cl, " dir %llx.%llx complete, -ENOENT\n",
ceph_vinop(dir));
d_add(dentry, NULL);
di->lease_shared_gen = atomic_read(&ci->i_shared_gen);
return NULL;
}
spin_unlock(&ci->i_ceph_lock);
}
Am I correct? So, how can we rework this code if it's wrong? What is your
vision? Do you mean that it's dead code? How can we check it?
Thanks,
Slava.
