[XFS] Fix up the calculation of the reservation overhead to hopefully

include all the components which make up the transaction in the ondisk log. Having this incomplete has shown up as problems on IRIX when some v2 log changes went in. The symptom was the msg of "xfs_log_write: reservation ran out. Need to up reservation" and was seen on synchronous writes on files with lots of holes (and therefore lots of extents). SGI-PV: 931457 SGI-Modid: xfs-linux:xfs-kern:23095a Signed-off-by: Tim Shimmin <tes@sgi.com> Signed-off-by: Nathan Scott <nathans@sgi.com>

[XFS] Fix up the calculation of the reservation overhead to hopefully
include all the components which make up the transaction in the ondisk log. Having this incomplete has shown up as problems on IRIX when some v2 log changes went in. The symptom was the msg of "xfs_log_write: reservation ran out. Need to up reservation" and was seen on synchronous writes on files with lots of holes (and therefore lots of extents). SGI-PV: 931457 SGI-Modid: xfs-linux:xfs-kern:23095a Signed-off-by: Tim Shimmin <tes@sgi.com> Signed-off-by: Nathan Scott <nathans@sgi.com>
Tim Shimmin · Nathan Scott
1 parent d52b44d07a
Showing 1 changed file with 41 additions and 13 deletions Side-by-side Diff
fs/xfs/xfs_log.c
@@ -3179,28 +3179,56 @@
 	 * 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 padding */
+	/* 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 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;
...	...	@@ -3179,28 +3179,56 @@
3179	3179	* and their unit amount is the total amount of space required.
3180	3180	*
3181	3181	* The following lines of code account for non-transaction data
3182		- * which occupy space in the on-disk log.
	3182	+ * which occupy space in the on-disk log.
	3183	+ *
	3184	+ * Normal form of a transaction is:
	3185	+ * <oph><trans-hdr><start-oph><reg1-oph><reg1><reg2-oph>...<commit-oph>
	3186	+ * and then there are LR hdrs, split-recs and roundoff at end of syncs.
	3187	+ *
	3188	+ * We need to account for all the leadup data and trailer data
	3189	+ * around the transaction data.
	3190	+ * And then we need to account for the worst case in terms of using
	3191	+ * more space.
	3192	+ * The worst case will happen if:
	3193	+ * - the placement of the transaction happens to be such that the
	3194	+ * roundoff is at its maximum
	3195	+ * - the transaction data is synced before the commit record is synced
	3196	+ * i.e. <transaction-data><roundoff> \| <commit-rec><roundoff>
	3197	+ * Therefore the commit record is in its own Log Record.
	3198	+ * This can happen as the commit record is called with its
	3199	+ * own region to xlog_write().
	3200	+ * This then means that in the worst case, roundoff can happen for
	3201	+ * the commit-rec as well.
	3202	+ * The commit-rec is smaller than padding in this scenario and so it is
	3203	+ * not added separately.
3183	3204	*/
3184	3205
	3206	+ /* for trans header */
	3207	+ unit_bytes += sizeof(xlog_op_header_t);
	3208	+ unit_bytes += sizeof(xfs_trans_header_t);
	3209	+
3185	3210	/* for start-rec */
3186		- unit_bytes += sizeof(xlog_op_header_t);
	3211	+ unit_bytes += sizeof(xlog_op_header_t);
3187	3212
3188		- /* for padding */
	3213	+ /* for LR headers */
	3214	+ num_headers = ((unit_bytes + log->l_iclog_size-1) >> log->l_iclog_size_log);
	3215	+ unit_bytes += log->l_iclog_hsize * num_headers;
	3216	+
	3217	+ /* for commit-rec LR header - note: padding will subsume the ophdr */
	3218	+ unit_bytes += log->l_iclog_hsize;
	3219	+
	3220	+ /* for split-recs - ophdrs added when data split over LRs */
	3221	+ unit_bytes += sizeof(xlog_op_header_t) * num_headers;
	3222	+
	3223	+ /* for roundoff padding for transaction data and one for commit record */
3189	3224	if (XFS_SB_VERSION_HASLOGV2(&log->l_mp->m_sb) &&
3190		- log->l_mp->m_sb.sb_logsunit > 1) {
	3225	+ log->l_mp->m_sb.sb_logsunit > 1) {
3191	3226	/* log su roundoff */
3192		- unit_bytes += log->l_mp->m_sb.sb_logsunit;
	3227	+ unit_bytes += 2*log->l_mp->m_sb.sb_logsunit;
3193	3228	} else {
3194	3229	/* BB roundoff */
3195		- unit_bytes += BBSIZE;
	3230	+ unit_bytes += 2*BBSIZE;
3196	3231	}
3197		-
3198		- /* for commit-rec */
3199		- unit_bytes += sizeof(xlog_op_header_t);
3200		-
3201		- /* for LR headers */
3202		- num_headers = ((unit_bytes + log->l_iclog_size-1) >> log->l_iclog_size_log);
3203		- unit_bytes += log->l_iclog_hsize * num_headers;
3204	3232
3205	3233	tic->t_unit_res = unit_bytes;
3206	3234	tic->t_curr_res = unit_bytes;