Cleaning up the code a little bit. attempt_plug_merge() traverses the plug list anyway, we can do the request counting there, so stack size is reduced a little bit. The motivation here is I suspect if we should count the requests for each queue (task could handle multiple disks in the meantime), but my test doesn't show it's worthy doing. If somebody proves we should do it, below change will make that more easier.
Unified · Split
| @@ -1167,7 +1167,7 @@ static bool bio_attempt_front_merge(struct request_queue *q, · 1166 unmodified lines | ||
| 1167 | 1167 | * true if merge was successful, otherwise false. |
| 1168 | 1168 | */ |
| 1169 | 1169 | static bool attempt_plug_merge(struct task_struct *tsk, struct request_queue *q, |
| 1170 | − struct bio *bio) | |
| 1170 | + struct bio *bio, unsigned int *request_count) | |
| 1171 | 1171 | { |
| 1172 | 1172 | struct blk_plug *plug; |
| 1173 | 1173 | struct request *rq; |
| @@ -1176,10 +1176,13 @@ static bool attempt_plug_merge(struct task_struct *tsk, struct request_queue *q, · 2 unmodified lines | ||
| 1176 | 1176 | plug = tsk->plug; |
| 1177 | 1177 | if (!plug) |
| 1178 | 1178 | goto out; |
| 1179 | + *request_count = 0; | |
| 1179 | 1180 | |
| 1180 | 1181 | list_for_each_entry_reverse(rq, &plug->list, queuelist) { |
| 1181 | 1182 | int el_ret; |
| 1182 | 1183 | |
| 1184 | + (*request_count)++; | |
| 1185 | + | |
| 1183 | 1186 | if (rq->q != q) |
| 1184 | 1187 | continue; |
| 1185 | 1188 | |
| @@ -1219,6 +1222,7 @@ static int __make_request(struct request_queue *q, struct bio *bio) · 33 unmodified lines | ||
| 1219 | 1222 | struct blk_plug *plug; |
| 1220 | 1223 | int el_ret, rw_flags, where = ELEVATOR_INSERT_SORT; |
| 1221 | 1224 | struct request *req; |
| 1225 | + unsigned int request_count = 0; | |
| 1222 | 1226 | |
| 1223 | 1227 | /* |
| 1224 | 1228 | * low level driver can indicate that it wants pages above a |
| @@ -1237,7 +1241,7 @@ static int __make_request(struct request_queue *q, struct bio *bio) · 12 unmodified lines | ||
| 1237 | 1241 | * Check if we can merge with the plugged list before grabbing |
| 1238 | 1242 | * any locks. |
| 1239 | 1243 | */ |
| 1240 | − if (attempt_plug_merge(current, q, bio)) | |
| 1244 | + if (attempt_plug_merge(current, q, bio, &request_count)) | |
| 1241 | 1245 | goto out; |
| 1242 | 1246 | |
| 1243 | 1247 | spin_lock_irq(q->queue_lock); |
| @@ -1302,9 +1306,8 @@ get_rq: · 58 unmodified lines | ||
| 1302 | 1306 | if (__rq->q != q) |
| 1303 | 1307 | plug->should_sort = 1; |
| 1304 | 1308 | } |
| 1305 | − if (plug->count >= BLK_MAX_REQUEST_COUNT) | |
| 1309 | + if (request_count >= BLK_MAX_REQUEST_COUNT) | |
| 1306 | 1310 | blk_flush_plug_list(plug, false); |
| 1307 | − plug->count++; | |
| 1308 | 1311 | list_add_tail(&req->queuelist, &plug->list); |
| 1309 | 1312 | drive_stat_acct(req, 1); |
| 1310 | 1313 | } else { |
| @@ -2634,7 +2637,6 @@ void blk_start_plug(struct blk_plug *plug) · 1323 unmodified lines | ||
| 2634 | 2637 | INIT_LIST_HEAD(&plug->list); |
| 2635 | 2638 | INIT_LIST_HEAD(&plug->cb_list); |
| 2636 | 2639 | plug->should_sort = 0; |
| 2637 | − plug->count = 0; | |
| 2638 | 2640 | |
| 2639 | 2641 | /* |
| 2640 | 2642 | * If this is a nested plug, don't actually assign it. It will be |
| @@ -2718,7 +2720,6 @@ void blk_flush_plug_list(struct blk_plug *plug, bool from_schedule) · 77 unmodified lines | ||
| 2718 | 2720 | return; |
| 2719 | 2721 | |
| 2720 | 2722 | list_splice_init(&plug->list, &list); |
| 2721 | − plug->count = 0; | |
| 2722 | 2723 | |
| 2723 | 2724 | if (plug->should_sort) { |
| 2724 | 2725 | list_sort(NULL, &list, plug_rq_cmp); |
| @@ -873,7 +873,6 @@ struct blk_plug { · 872 unmodified lines | ||
| 873 | 873 | struct list_head list; |
| 874 | 874 | struct list_head cb_list; |
| 875 | 875 | unsigned int should_sort; |
| 876 | − unsigned int count; | |
| 877 | 876 | }; |
| 878 | 877 | #define BLK_MAX_REQUEST_COUNT 16 |
| 879 | 878 | |