On Thu, May 14, 2020 at 08:10:09AM -0400, Jeff Layton wrote:
> On Thu, 2020-05-14 at 12:14 +0100, Luis Henriques wrote:
> > Similarly to commit 03f219041fdb ("ceph: check i_nlink while converting
> > a file handle to dentry"), this fixes another corner case with
> > name_to_handle_at/open_by_handle_at. The issue has been detected by
> > xfstest generic/467, when doing:
> >
> > - name_to_handle_at("/cephfs/myfile")
> > - open("/cephfs/myfile")
> > - unlink("/cephfs/myfile")
> > - open_by_handle_at()
> >
> > The call to open_by_handle_at should not fail because the file still
> > exists and we do have a valid handle to it.
> >
> > Signed-off-by: Luis Henriques <lhenriques@xxxxxxxx>
> > ---
> > fs/ceph/export.c | 13 +++++++++++--
> > 1 file changed, 11 insertions(+), 2 deletions(-)
> >
> > diff --git a/fs/ceph/export.c b/fs/ceph/export.c
> > index 79dc06881e78..8556df9d94d0 100644
> > --- a/fs/ceph/export.c
> > +++ b/fs/ceph/export.c
> > @@ -171,12 +171,21 @@ struct inode *ceph_lookup_inode(struct super_block *sb, u64 ino)
> >
> > static struct dentry *__fh_to_dentry(struct super_block *sb, u64 ino)
> > {
> > + struct ceph_inode_info *ci;
> > struct inode *inode = __lookup_inode(sb, ino);
> > +
> > if (IS_ERR(inode))
> > return ERR_CAST(inode);
> > if (inode->i_nlink == 0) {
> > - iput(inode);
> > - return ERR_PTR(-ESTALE);
> > + bool is_open;
> > + ci = ceph_inode(inode);
> > + spin_lock(&ci->i_ceph_lock);
> > + is_open = __ceph_is_file_opened(ci);
> > + spin_unlock(&ci->i_ceph_lock);
> > + if (!is_open) {
> > + iput(inode);
> > + return ERR_PTR(-ESTALE);
> > + }
> > }
> > return d_obtain_alias(inode);
> > }
>
> Thanks Luis. Out of curiousity, is there any reason we shouldn't ignore
> the i_nlink value here? Does anything obviously break if we do?
Yes, the scenario described in commit 03f219041fdb is still valid, which
is basically the same but without the extra open(2):
- name_to_handle_at("/cephfs/myfile")
- unlink("/cephfs/myfile")
- open_by_handle_at()
The open_by_handle_at man page isn't really clear about these 2 scenarios,
but generic/426 will fail if -ESTALE isn't returned. Want me to add a
comment to the code, describing these 2 scenarios?
Cheers,
--
Luis
