On Wed, 2022-03-30 at 14:44 +0800, xiubli@xxxxxxxxxx wrote:
> From: Xiubo Li <xiubli@xxxxxxxxxx>
>
> The type of 'r_attempts' in kernel 'ceph_mds_request' is 'int',
> while in 'ceph_mds_request_head' the type of 'num_retry' is '__u8'.
> So in case the request retries exceeding 256 times, the MDS will
> receive a incorrect retry seq.
>
> In this case it's ususally a bug in MDS and continue retrying the
> request makes no sense. For now let's limit it to 256. In future
> this could be fixed in ceph code, so avoid using the hardcode here.
>
> Signed-off-by: Xiubo Li <xiubli@xxxxxxxxxx>
> ---
> fs/ceph/mds_client.c | 25 +++++++++++++++++++++++--
> 1 file changed, 23 insertions(+), 2 deletions(-)
>
> diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
> index e11d31401f12..f476c65fb985 100644
> --- a/fs/ceph/mds_client.c
> +++ b/fs/ceph/mds_client.c
> @@ -2679,7 +2679,28 @@ static int __prepare_send_request(struct ceph_mds_session *session,
> struct ceph_mds_client *mdsc = session->s_mdsc;
> struct ceph_mds_request_head_old *rhead;
> struct ceph_msg *msg;
> - int flags = 0;
> + int flags = 0, max_retry;
> +
> + /*
> + * The type of 'r_attempts' in kernel 'ceph_mds_request'
> + * is 'int', while in 'ceph_mds_request_head' the type of
> + * 'num_retry' is '__u8'. So in case the request retries
> + * exceeding 256 times, the MDS will receive a incorrect
> + * retry seq.
> + *
> + * In this case it's ususally a bug in MDS and continue
> + * retrying the request makes no sense.
> + *
> + * In future this could be fixed in ceph code, so avoid
> + * using the hardcode here.
> + */
> + max_retry = sizeof_field(struct ceph_mds_request_head, num_retry);
> + max_retry = 1 << (max_retry * BITS_PER_BYTE);
> + if (req->r_attempts >= max_retry) {
> + pr_warn_ratelimited("%s request tid %llu seq overflow\n",
> + __func__, req->r_tid);
> + return -EMULTIHOP;
> + }
>
> req->r_attempts++;
> if (req->r_inode) {
> @@ -2691,7 +2712,7 @@ static int __prepare_send_request(struct ceph_mds_session *session,
> else
> req->r_sent_on_mseq = -1;
> }
> - dout("prepare_send_request %p tid %lld %s (attempt %d)\n", req,
> + dout("%s %p tid %lld %s (attempt %d)\n", __func__, req,
> req->r_tid, ceph_mds_op_name(req->r_op), req->r_attempts);
>
> if (test_bit(CEPH_MDS_R_GOT_UNSAFE, &req->r_req_flags)) {
Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
