linux内核md源代码解读 八 阵列同步二：同步过程

7411         blk_start_plug(&plug);  
7412         while (j < max_sectors) {  
7413                 sector_t sectors;  
7414   
7415                 skipped = 0;  
7416   
7417                 if (!test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery) &&  
7418                     ((mddev->curr_resync > mddev->curr_resync_completed &&  
7419                       (mddev->curr_resync - mddev->curr_resync_completed)  
7420                       > (max_sectors >> 4)) ||  
7421                      (j - mddev->curr_resync_completed)*2  
7422                      >= mddev->resync_max - mddev->curr_resync_completed  
7423                             )) {  
7424                         /* time to update curr_resync_completed */
7425                         wait_event(mddev->recovery_wait,  
7426                                    atomic_read(&mddev->recovery_active) == 0);  
7427                         mddev->curr_resync_completed = j;  
7428                         set_bit(MD_CHANGE_CLEAN, &mddev->flags);  
7429                         sysfs_notify(&mddev->kobj, NULL, "sync_completed");  
7430                 }  
7431   
7432                 while (j >= mddev->resync_max && !kthread_should_stop()) {  
7433                         /* As this condition is controlled by user-space, 
7434                          * we can block indefinitely, so use '_interruptible' 
7435                          * to avoid triggering warnings. 
7436                          */
7437                         flush_signals(current); /* just in case */
7438                         wait_event_interruptible(mddev->recovery_wait,  
7439                                                  mddev->resync_max > j  
7440                                                  || kthread_should_stop());  
7441                 }  
7442   
7443                 if (kthread_should_stop())  
7444                         goto interrupted;  
7445   
7446                 sectors = mddev->pers->sync_request(mddev, j, &skipped,  
7447                                                   currspeed < speed_min(mddev));  
7448                 if (sectors == 0) {  
7449                         set_bit(MD_RECOVERY_INTR, &mddev->recovery);  
7450                         goto out;  
7451                 }  
7452   
7453                 if (!skipped) { /* actual IO requested */
7454                         io_sectors += sectors;  
7455                         atomic_add(sectors, &mddev->recovery_active);  
7456                 }  
7457   
7458                 if (test_bit(MD_RECOVERY_INTR, &mddev->recovery))  
7459                         break;  
7460   
7461                 j += sectors;  
7462                 if (j>1) mddev->curr_resync = j;  
7463                 mddev->curr_mark_cnt = io_sectors;  
7464                 if (last_check == 0)  
7465                         /* this is the earliest that rebuild will be 
7466                          * visible in /proc/mdstat 
7467                          */
7468                         md_new_event(mddev);  
7469   
7470                 if (last_check + window > io_sectors || j == max_sectors)  
7471                         continue;  
7472   
7473                 last_check = io_sectors;  
7474         repeat:  
7475                 if (time_after_eq(jiffies, mark[last_mark] + SYNC_MARK_STEP )) {  
7476                         /* step marks */
7477                         int next = (last_mark+1) % SYNC_MARKS;  
7478   
7479                         mddev->resync_mark = mark[next];  
7480                         mddev->resync_mark_cnt = mark_cnt[next];  
7481                         mark[next] = jiffies;  
7482                         mark_cnt[next] = io_sectors - atomic_read(&mddev->recovery_active);  
7483                         last_mark = next;  
7484                 }  
7485   
7486   

7487                 if (kthread_should_stop())  
7488                         goto interrupted;  
7489   
7490   
7491                 /* 
7492                  * this loop exits only if either when we are slower than 
7493                  * the 'hard' speed limit, or the system was IO-idle for 
7494                  * a jiffy. 
7495                  * the system might be non-idle CPU-wise, but we only care 
7496                  * about not overloading the IO subsystem. (things like an 
7497                  * e2fsck being done on the RAID array should execute fast) 
7498                  */
7499                 cond_resched();  
7500   
7501                 currspeed = ((unsigned long)(io_sectors-mddev->resync_mark_cnt))/2  
7502                         /((jiffies-mddev->resync_mark)/HZ +1) +1;  
7503   
7504                 if (currspeed > speed_min(mddev)) {  
7505                         if ((currspeed > speed_max(mddev)) ||  
7506                                         !is_mddev_idle(mddev, 0)) {  
7507                                 msleep(500);  
7508                                 goto repeat;  
7509                         }  
7510                 }  
7511         }  
7512         printk(KERN_INFO "md: %s: %s done.n",mdname(mddev), desc);

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