[LU-11426] 2/2 Olafs agree: changelog entries are emitted out of order

Duplicate — Thu, 24 Oct 2019 21:23:56 +0000

When storing changelogs we do not strictly order the entries with respect to index.

int mdd_changelog_store(const struct lu_env *env, struct mdd_device *mdd,
                        struct llog_changelog_rec *rec, struct thandle *th)
{
        ...

        /* llog_lvfs_write_rec sets the llog tail len */
        rec->cr_hdr.lrh_type = CHANGELOG_REC;
        rec->cr.cr_time = cl_time();

        spin_lock(&mdd->mdd_cl.mc_lock);
        /* NB: I suppose it's possible llog_add adds out of order wrt cr_index,
         * but as long as the MDD transactions are ordered correctly for e.g.
         * rename conflicts, I don't think this should matter. */
        rec->cr.cr_index = ++mdd->mdd_cl.mc_index;
        spin_unlock(&mdd->mdd_cl.mc_lock);

        ctxt = llog_get_context(obd, LLOG_CHANGELOG_ORIG_CTXT);
        if (ctxt == NULL)
                return -ENXIO;

        llog_th = thandle_get_sub(env, th, ctxt->loc_handle->lgh_obj);
        if (IS_ERR(llog_th))
                GOTO(out_put, rc = PTR_ERR(llog_th));

        /* nested journal transaction */
        rc = llog_add(env, ctxt->loc_handle, &rec->cr_hdr, NULL, llog_th);

This may not be a bug in itself but it means that a changelog consumer must account for gaps in the sequence when clearing changelog entries.

Whamcloud Community JIRA

[LU-11426] 2/2 Olafs agree: changelog entries are emitted out of order