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4097 logical_sector = bi->bi_sector & ~((sector_t)STRIPE_SECTORS-1); 4098 last_sector = bi->bi_sector + (bi->bi_size>>9); 4099 bi->bi_next = NULL; 4100 bi->bi_phys_segments = 1; /* over-loaded to count active stripes */
4102 for (;logical_sector < last_sector; logical_sector += STRIPE_SECTORS) {
4103 DEFINE_WAIT(w);
4104 int previous;
4105
4106 retry:
4107 previous = 0;
4108 prepare_to_wait(&conf->wait_for_overlap, &w, TASK_UNINTERRUPTIBLE);
...
4134
4135 new_sector = raid5_compute_sector(conf, logical_sector,
4136 previous,
4137 &dd_idx, NULL);
4138 pr_debug("raid456: make_request, sector %llu logical %llu\n",
4139 (unsigned long long)new_sector,
4140 (unsigned long long)logical_sector);
4141
4142 sh = get_active_stripe(conf, new_sector, previous,
4143 (bi->bi_rw&RWA_MASK), 0);在处理条带的时候还须要做到相互排斥。不能有两个线程在同一时候操作同一个条带。
比方说同步线程在同步这个条带，raid5d在写这个条带，那么就会产生非预期的结果。
4144 if (sh) {
....
4186 if (test_bit(STRIPE_EXPANDING, &sh->state) ||
4187 !add_stripe_bio(sh, bi, dd_idx, rw)) {
4188 /* Stripe is busy expanding or
4189 * add failed due to overlap. Flush everything
4190 * and wait a while
4191 */
4192 md_wakeup_thread(mddev->thread);
4193 release_stripe(sh);
4194 schedule();
4195 goto retry;
4196 }
4197 finish_wait(&conf->wait_for_overlap, &w);
4198 set_bit(STRIPE_HANDLE, &sh->state);
4199 clear_bit(STRIPE_DELAYED, &sh->state);
4200 if ((bi->bi_rw & REQ_SYNC) &&
4201 !test_and_set_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
4202 atomic_inc(&conf->preread_active_stripes);
4203 release_stripe_plug(mddev, sh);
4204 } else {
4205 /* cannot get stripe for read-ahead, just give-up */
4206 clear_bit(BIO_UPTODATE, &bi->bi_flags);
4207 finish_wait(&conf->wait_for_overlap, &w);
4208 break;
4209 }
4210 }3245 if (test_bit(R5_Wantfill, &dev->flags)) 3246 s->to_fill++; 3247 else if (dev->toread) 3248 s->to_read++;
3472 if (s.to_read || s.non_overwrite 3473 || (conf->level == 6 && s.to_write && s.failed) 3474 || (s.syncing && (s.uptodate + s.compute < disks)) 3475 || s.replacing 3476 || s.expanding) 3477 handle_stripe_fill(sh, &s, disks);
2696 set_bit(R5_LOCKED, &dev->flags); 2697 set_bit(R5_Wantread, &dev->flags); 2698 s->locked++;
1745 if (uptodate) {
1746 set_bit(R5_UPTODATE, &sh->dev[i].flags);
...
1824 rdev_dec_pending(rdev, conf->mddev);
1825 clear_bit(R5_LOCKED, &sh->dev[i].flags);
1826 set_bit(STRIPE_HANDLE, &sh->state);
1827 release_stripe(sh);3231 if (test_bit(R5_UPTODATE, &dev->flags) && dev->toread &&
3232 !test_bit(STRIPE_BIOFILL_RUN, &sh->state))
3233 set_bit(R5_Wantfill, &dev->flags);
3234
3235 /* now count some things */
3236 if (test_bit(R5_LOCKED, &dev->flags))
3237 s->locked++;
3238 if (test_bit(R5_UPTODATE, &dev->flags))
3239 s->uptodate++;
3240 if (test_bit(R5_Wantcompute, &dev->flags)) {
3241 s->compute++;
3242 BUG_ON(s->compute > 2);
3243 }
3244
3245 if (test_bit(R5_Wantfill, &dev->flags))
3246 s->to_fill++;3426 if (s.to_fill && !test_bit(STRIPE_BIOFILL_RUN, &sh->state)) {
3427 set_bit(STRIPE_OP_BIOFILL, &s.ops_request);
3428 set_bit(STRIPE_BIOFILL_RUN, &sh->state);
3429 }1378 if (test_bit(STRIPE_OP_BIOFILL, &ops_request)) {
1379 ops_run_biofill(sh);
1380 overlap_clear++;
1381 }
812static void ops_run_biofill(struct stripe_head *sh)
813{
814 struct dma_async_tx_descriptor *tx = NULL;
815 struct async_submit_ctl submit;
816 int i;
817
818 pr_debug("%s: stripe %llu\n", __func__,
819 (unsigned long long)sh->sector);
820
821 for (i = sh->disks; i--; ) {
822 struct r5dev *dev = &sh->dev[i];
823 if (test_bit(R5_Wantfill, &dev->flags)) {
824 struct bio *rbi;
825 spin_lock_irq(&sh->stripe_lock);
826 dev->read = rbi = dev->toread;
827 dev->toread = NULL;
828 spin_unlock_irq(&sh->stripe_lock);
829 while (rbi && rbi->bi_sector <
830 dev->sector + STRIPE_SECTORS) {
831 tx = async_copy_data(0, rbi, dev->page,
832 dev->sector, tx);
833 rbi = r5_next_bio(rbi, dev->sector);
834 }
835 }
836 }
837
838 atomic_inc(&sh->count);
839 init_async_submit(&submit, ASYNC_TX_ACK, tx, ops_complete_biofill, sh, NULL);
840 async_trigger_callback(&submit);
841}
并且越是复杂的代码就越是风情万种、婀娜多姿，前提是你要懂得怎样走入她的内心里才干体会得到。等真正体会到的时候你就会拍案叫绝，从而获得征服的快感久久不能忘怀。在征服了这样一个又一个风情万种的代码之后。你的追求就不再局限于肉体之上，转而追求精神上的高度，像欧洲建筑师一样去设计大教堂，然后花个600多年把哥特式的科隆大教堂建好，这才叫艺术。
好吧，那个时候你我都已经不在了，但那种精神始终是你我要追求的境地。
769static void ops_complete_biofill(void *stripe_head_ref)
770{
771 struct stripe_head *sh = stripe_head_ref;
772 struct bio *return_bi = NULL;
773 int i;
774
775 pr_debug("%s: stripe %llu\n", __func__,
776 (unsigned long long)sh->sector);
777
778 /* clear completed biofills */
779 for (i = sh->disks; i--; ) {
780 struct r5dev *dev = &sh->dev[i];
781
782 /* acknowledge completion of a biofill operation */
783 /* and check if we need to reply to a read request,
784 * new R5_Wantfill requests are held off until
785 * !STRIPE_BIOFILL_RUN
786 */
787 if (test_and_clear_bit(R5_Wantfill, &dev->flags)) {
788 struct bio *rbi, *rbi2;
789
790 BUG_ON(!dev->read);
791 rbi = dev->read;
792 dev->read = NULL;
793 while (rbi && rbi->bi_sector <
794 dev->sector + STRIPE_SECTORS) {
795 rbi2 = r5_next_bio(rbi, dev->sector);
796 if (!raid5_dec_bi_active_stripes(rbi)) {
797 rbi->bi_next = return_bi;
798 return_bi = rbi;
799 }
800 rbi = rbi2;
801 }
802 }
803 }
804 clear_bit(STRIPE_BIOFILL_RUN, &sh->state);
805
806 return_io(return_bi);
807
808 set_bit(STRIPE_HANDLE, &sh->state);
809 release_stripe(sh);
810}177static void return_io(struct bio *return_bi)
178{
179 struct bio *bi = return_bi;
180 while (bi) {
181
182 return_bi = bi->bi_next;
183 bi->bi_next = NULL;
184 bi->bi_size = 0;
185 bio_endio(bi, 0);
186 bi = return_bi;
187 }
188}
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原文地址：http://www.cnblogs.com/mengfanrong/p/4713262.html
