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-rw-r--r--fs/xfs/xfs_log.c54
1 files changed, 41 insertions, 13 deletions
diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index 1cd2ac16387..42975cb9e53 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;