Fix for bug 596453: multiple mirror image failures cause lvm repair... added upstream on 2010/08/17 The lvm repair issues I believe are the superficial symptoms of this bug - there are worse issues that are not as clearly seen. From my inline comments: * If the mirror was successfully recovered, we want to always * force every machine to write to all devices - otherwise, * corruption will occur. Here's how: * Node1 suffers a failure and marks a region out-of-sync * Node2 attempts a write, gets by is_remote_recovering, * and queries the sync status of the region - finding * it out-of-sync. * Node2 thinks the write should be a nosync write, but it * hasn't suffered the drive failure that Node1 has yet. * It then issues a generic_make_request directly to * the primary image only - which is exactly the device * that has suffered the failure. * Node2 suffers a lost write - which completely bypasses the * mirror layer because it had gone through generic_m_r. * The file system will likely explode at this point due to * I/O errors. If it wasn't the primary that failed, it is * easily possible in this case to issue writes to just one * of the remaining images - also leaving the mirror inconsistent. * * We let in_sync() return 1 in a cluster regardless of what is * in the bitmap once recovery has successfully completed on a * mirror. This ensures the mirroring code will continue to * attempt to write to all mirror images. The worst that can * happen for reads is that additional read attempts may be * taken. Index: cluster/cmirror/src/functions.c =================================================================== --- cluster.orig/cmirror/src/functions.c +++ cluster/cmirror/src/functions.c @@ -53,6 +53,7 @@ struct log_c { time_t delay; /* limits how fast a resume can happen after suspend */ int touched; + int in_sync; /* An in-sync that stays set until suspend/resume */ uint32_t region_size; uint32_t region_count; uint64_t sync_count; @@ -718,6 +719,7 @@ static int clog_resume(struct clog_tfr * if (!lc) return -EINVAL; + lc->in_sync = 0; switch (lc->resume_override) { case 1000: LOG_ERROR("[%s] Additional resume issued before suspend", @@ -971,6 +973,41 @@ static int clog_in_sync(struct clog_tfr return -EINVAL; *rtn = log_test_bit(lc->sync_bits, region); + + /* + * If the mirror was successfully recovered, we want to always + * force every machine to write to all devices - otherwise, + * corruption will occur. Here's how: + * Node1 suffers a failure and marks a region out-of-sync + * Node2 attempts a write, gets by is_remote_recovering, + * and queries the sync status of the region - finding + * it out-of-sync. + * Node2 thinks the write should be a nosync write, but it + * hasn't suffered the drive failure that Node1 has yet. + * It then issues a generic_make_request directly to + * the primary image only - which is exactly the device + * that has suffered the failure. + * Node2 suffers a lost write - which completely bypasses the + * mirror layer because it had gone through generic_m_r. + * The file system will likely explode at this point due to + * I/O errors. If it wasn't the primary that failed, it is + * easily possible in this case to issue writes to just one + * of the remaining images - also leaving the mirror inconsistent. + * + * We let in_sync() return 1 in a cluster regardless of what is + * in the bitmap once recovery has successfully completed on a + * mirror. This ensures the mirroring code will continue to + * attempt to write to all mirror images. The worst that can + * happen for reads is that additional read attempts may be + * taken. + * + * Futher investigation may be required to determine if there are + * similar possible outcomes when the mirror is in the process of + * recovering. In that case, lc->in_sync would not have been set + * yet. + */ + if (!*rtn && lc->in_sync) + *rtn = 1; if (*rtn) LOG_DBG("[%s] Region is in-sync: %llu", SHORT_UUID(lc->uuid), (unsigned long long)region); @@ -1302,8 +1339,8 @@ static int clog_set_region_sync(struct c lc->skip_bit_warning = lc->region_count; if (pkg->region > (lc->skip_bit_warning + 5)) { - LOG_ERROR("*** Region #%llu skipped during recovery ***", - (unsigned long long)lc->skip_bit_warning); + LOG_SPRINT("*** Region #%llu skipped during recovery ***", + (unsigned long long)lc->skip_bit_warning); lc->skip_bit_warning = lc->region_count; #ifdef DEBUG kill(getpid(), SIGUSR1); @@ -1344,6 +1381,9 @@ static int clog_set_region_sync(struct c "(lc->sync_count > lc->region_count) - this is bad", tfr->seq, SHORT_UUID(lc->uuid), tfr->originator); + if (lc->sync_count == lc->region_count) + lc->in_sync = 1; + tfr->data_size = 0; return 0; }