On Mon, 2022-02-07 at 13:03 +0800, xiubli@xxxxxxxxxx wrote: > From: Xiubo Li <xiubli@xxxxxxxxxx> > > If MDS return ESTALE, that means the MDS has already iterated all > the possible active MDSes including the auth MDS or the inode is > under purging. No need to retry in auth MDS and will just return > ESTALE directly. > When you say "purging" here, do you mean that it's effectively being cleaned up after being unlinked? Or is it just being purged from the MDS's cache? > Or it will cause definite loop for retrying it. > > URL: https://tracker.ceph.com/issues/53504 > Signed-off-by: Xiubo Li <xiubli@xxxxxxxxxx> > --- > fs/ceph/mds_client.c | 29 ----------------------------- > 1 file changed, 29 deletions(-) > > diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c > index 93e5e3c4ba64..c918d2ac8272 100644 > --- a/fs/ceph/mds_client.c > +++ b/fs/ceph/mds_client.c > @@ -3368,35 +3368,6 @@ static void handle_reply(struct ceph_mds_session *session, struct ceph_msg *msg) > > result = le32_to_cpu(head->result); > > - /* > - * Handle an ESTALE > - * if we're not talking to the authority, send to them > - * if the authority has changed while we weren't looking, > - * send to new authority > - * Otherwise we just have to return an ESTALE > - */ > - if (result == -ESTALE) { > - dout("got ESTALE on request %llu\n", req->r_tid); > - req->r_resend_mds = -1; > - if (req->r_direct_mode != USE_AUTH_MDS) { > - dout("not using auth, setting for that now\n"); > - req->r_direct_mode = USE_AUTH_MDS; > - __do_request(mdsc, req); > - mutex_unlock(&mdsc->mutex); > - goto out; > - } else { > - int mds = __choose_mds(mdsc, req, NULL); > - if (mds >= 0 && mds != req->r_session->s_mds) { > - dout("but auth changed, so resending\n"); > - __do_request(mdsc, req); > - mutex_unlock(&mdsc->mutex); > - goto out; > - } > - } > - dout("have to return ESTALE on request %llu\n", req->r_tid); > - } > - > - > if (head->safe) { > set_bit(CEPH_MDS_R_GOT_SAFE, &req->r_req_flags); > __unregister_request(mdsc, req); (cc'ing Greg, Sage and Zheng) This patch sort of contradicts the original design, AFAICT, and I'm not sure what the correct behavior should be. I could use some clarification. The original code (from the 2009 merge) would tolerate 2 ESTALEs before giving up and returning that to userland. Then in 2010, Greg added this commit: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e55b71f802fd448a79275ba7b263fe1a8639be5f ...which would presumably make it retry indefinitely as long as the auth MDS kept changing. Then, Zheng made this change in 2013: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ca18bede048e95a749d13410ce1da4ad0ffa7938 ...which seems to try to do the same thing, but detected the auth mds change in a different way. Is that where livelock detection was broken? Or was there some corresponding change to __choose_mds that should prevent infinitely looping on the same request? In NFS, ESTALE errors mean that the filehandle (inode) no longer exists and that the server has forgotten about it. Does it mean the same thing to the ceph MDS? Has the behavior of the MDS changed such that these retries are no longer necessary on an ESTALE? If so, when did this change, and does the client need to do anything to detect what behavior it should be using? -- Jeff Layton <jlayton@xxxxxxxxxx>
