diff options
| -rw-r--r-- | fs/xfs/xfs_log.c | 54 |
1 files changed, 41 insertions, 13 deletions
diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c index 1cd2ac163877..42975cb9e538 100644 --- a/fs/xfs/xfs_log.c +++ b/fs/xfs/xfs_log.c @@ -3179,29 +3179,57 @@ xlog_ticket_get(xlog_t *log, * and their unit amount is the total amount of space required. * * The following lines of code account for non-transaction data - * which occupy space in the on-disk log. + * which occupy space in the on-disk log. + * + * Normal form of a transaction is: + * <oph><trans-hdr><start-oph><reg1-oph><reg1><reg2-oph>...<commit-oph> + * and then there are LR hdrs, split-recs and roundoff at end of syncs. + * + * We need to account for all the leadup data and trailer data + * around the transaction data. + * And then we need to account for the worst case in terms of using + * more space. + * The worst case will happen if: + * - the placement of the transaction happens to be such that the + * roundoff is at its maximum + * - the transaction data is synced before the commit record is synced + * i.e. <transaction-data><roundoff> | <commit-rec><roundoff> + * Therefore the commit record is in its own Log Record. + * This can happen as the commit record is called with its + * own region to xlog_write(). + * This then means that in the worst case, roundoff can happen for + * the commit-rec as well. + * The commit-rec is smaller than padding in this scenario and so it is + * not added separately. */ + /* for trans header */ + unit_bytes += sizeof(xlog_op_header_t); + unit_bytes += sizeof(xfs_trans_header_t); + /* for start-rec */ - unit_bytes += sizeof(xlog_op_header_t); + unit_bytes += sizeof(xlog_op_header_t); + + /* for LR headers */ + num_headers = ((unit_bytes + log->l_iclog_size-1) >> log->l_iclog_size_log); + unit_bytes += log->l_iclog_hsize * num_headers; - /* for padding */ + /* for commit-rec LR header - note: padding will subsume the ophdr */ + unit_bytes += log->l_iclog_hsize; + + /* for split-recs - ophdrs added when data split over LRs */ + unit_bytes += sizeof(xlog_op_header_t) * num_headers; + + /* for roundoff padding for transaction data and one for commit record */ if (XFS_SB_VERSION_HASLOGV2(&log->l_mp->m_sb) && - log->l_mp->m_sb.sb_logsunit > 1) { + log->l_mp->m_sb.sb_logsunit > 1) { /* log su roundoff */ - unit_bytes += log->l_mp->m_sb.sb_logsunit; + unit_bytes += 2*log->l_mp->m_sb.sb_logsunit; } else { /* BB roundoff */ - unit_bytes += BBSIZE; + unit_bytes += 2*BBSIZE; } - /* for commit-rec */ - unit_bytes += sizeof(xlog_op_header_t); - - /* for LR headers */ - num_headers = ((unit_bytes + log->l_iclog_size-1) >> log->l_iclog_size_log); - unit_bytes += log->l_iclog_hsize * num_headers; - tic->t_unit_res = unit_bytes; tic->t_curr_res = unit_bytes; tic->t_cnt = cnt; |