On Wed, Apr 17, 2019 at 2:40 PM Jeff Layton <jlayton@xxxxxxxxxx> wrote:
>
> It's possible for us to issue a lookup to revalidate a dentry
> concurrently with a rename. If done in the right order, then we could
> end up processing dentry info in the reply that no longer reflects the
> state of the dentry.
>
> If req->r_dentry->d_name differs from the one in the trace, then just
> ignore the trace in the reply. We only need to do this however if the
> parent's i_rwsem is not held.
>
> Reported-by: "Yan, Zheng" <zyan@xxxxxxxxxx>
> Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
> ---
> fs/ceph/inode.c | 17 ++++++++++++++++-
> 1 file changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
> index b33ba16f7ae8..e1ac10f960dd 100644
> --- a/fs/ceph/inode.c
> +++ b/fs/ceph/inode.c
> @@ -1163,6 +1163,20 @@ static int splice_dentry(struct dentry **pdn, struct inode *in)
> return 0;
> }
>
> +static bool
Probably should make this return int instead. I'll change that in
tree, but it shouldn't change the code materially.
> +d_name_cmp(struct dentry *dentry, const char *name, size_t len)
> +{
> + int ret;
> +
> + /* take d_lock to ensure dentry->d_name stability */
> + spin_lock(&dentry->d_lock);
> + ret = dentry->d_name.len - len;
> + if (!ret)
> + ret = memcmp(dentry->d_name.name, name, len);
> + spin_unlock(&dentry->d_lock);
> + return ret;
> +}
> +
> /*
> * Incorporate results into the local cache. This is either just
> * one inode, or a directory, dentry, and possibly linked-to inode (e.g.,
> @@ -1412,7 +1426,8 @@ int ceph_fill_trace(struct super_block *sb, struct ceph_mds_request *req)
> err = splice_dentry(&req->r_dentry, in);
> if (err < 0)
> goto done;
> - } else if (rinfo->head->is_dentry) {
> + } else if (rinfo->head->is_dentry &&
> + !d_name_cmp(req->r_dentry, rinfo->dname, rinfo->dname_len)) {
> struct ceph_vino *ptvino = NULL;
>
> if ((le32_to_cpu(rinfo->diri.in->cap.caps) & CEPH_CAP_FILE_SHARED) ||
> --
> 2.20.1
>
--
Jeff Layton <jlayton@xxxxxxxxxx>
