[PATCH] md: auto-correct correctable read errors in raid10

Largely just a cross-port from raid1.

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 112 insertions, 15 deletions

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 1fa70c34b7d2..64bb4ddc6798 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -209,6 +209,7 @@ static void reschedule_retry(r10bio_t *r10_bio)
 
         spin_lock_irqsave(&conf->device_lock, flags);
         list_add(&r10_bio->retry_list, &conf->retry_list);
+        conf->nr_queued ++;
         spin_unlock_irqrestore(&conf->device_lock, flags);
 
         md_wakeup_thread(mddev->thread);
@@ -254,9 +255,9 @@ static int raid10_end_read_request(struct bio *bio, unsigned int bytes_done, int
         /*
          * this branch is our 'one mirror IO has finished' event handler:
          */
-        if (!uptodate)
-                md_error(r10_bio->mddev, conf->mirrors[dev].rdev);
-        else
+        update_head_pos(slot, r10_bio);
+
+        if (uptodate) {
                 /*
                  * Set R10BIO_Uptodate in our master bio, so that
                  * we will return a good error code to the higher
@@ -267,15 +268,8 @@ static int raid10_end_read_request(struct bio *bio, unsigned int bytes_done, int
                  * wait for the 'master' bio.
                  */
                 set_bit(R10BIO_Uptodate, &r10_bio->state);
-
-        update_head_pos(slot, r10_bio);
-
-        /*
-         * we have only one bio on the read side
-         */
-        if (uptodate)
                 raid_end_bio_io(r10_bio);
-        else {
+        } else {
                 /*
                  * oops, read error:
                  */
@@ -714,6 +708,33 @@ static void allow_barrier(conf_t *conf)
         wake_up(&conf->wait_barrier);
 }
 
+static void freeze_array(conf_t *conf)
+{
+        /* stop syncio and normal IO and wait for everything to
+         * go quite.
+         * We increment barrier and nr_waiting, and then
+         * wait until barrier+nr_pending match nr_queued+2
+         */
+        spin_lock_irq(&conf->resync_lock);
+        conf->barrier++;
+        conf->nr_waiting++;
+        wait_event_lock_irq(conf->wait_barrier,
+                            conf->barrier+conf->nr_pending == conf->nr_queued+2,
+                            conf->resync_lock,
+                            raid10_unplug(conf->mddev->queue));
+        spin_unlock_irq(&conf->resync_lock);
+}
+
+static void unfreeze_array(conf_t *conf)
+{
+        /* reverse the effect of the freeze */
+        spin_lock_irq(&conf->resync_lock);
+        conf->barrier--;
+        conf->nr_waiting--;
+        wake_up(&conf->wait_barrier);
+        spin_unlock_irq(&conf->resync_lock);
+}
+
 static int make_request(request_queue_t *q, struct bio * bio)
 {
         mddev_t *mddev = q->queuedata;
@@ -1338,6 +1359,7 @@ static void raid10d(mddev_t *mddev)
                         break;
                 r10_bio = list_entry(head->prev, r10bio_t, retry_list);
                 list_del(head->prev);
+                conf->nr_queued--;
                 spin_unlock_irqrestore(&conf->device_lock, flags);
 
                 mddev = r10_bio->mddev;
@@ -1350,6 +1372,78 @@ static void raid10d(mddev_t *mddev)
                         unplug = 1;
                 } else {
                         int mirror;
+                        /* we got a read error. Maybe the drive is bad.  Maybe just
+                         * the block and we can fix it.
+                         * We freeze all other IO, and try reading the block from
+                         * other devices.  When we find one, we re-write
+                         * and check it that fixes the read error.
+                         * This is all done synchronously while the array is
+                         * frozen.
+                         */
+                        int sect = 0; /* Offset from r10_bio->sector */
+                        int sectors = r10_bio->sectors;
+                        freeze_array(conf);
+                        if (mddev->ro == 0) while(sectors) {
+                                int s = sectors;
+                                int sl = r10_bio->read_slot;
+                                int success = 0;
+
+                                if (s > (PAGE_SIZE>>9))
+                                        s = PAGE_SIZE >> 9;
+
+                                do {
+                                        int d = r10_bio->devs[sl].devnum;
+                                        rdev = conf->mirrors[d].rdev;
+                                        if (rdev &&
+                                            test_bit(In_sync, &rdev->flags) &&
+                                            sync_page_io(rdev->bdev,
+                                                         r10_bio->devs[sl].addr +
+                                                         sect + rdev->data_offset,
+                                                         s<<9,
+                                                         conf->tmppage, READ))
+                                                success = 1;
+                                        else {
+                                                sl++;
+                                                if (sl == conf->copies)
+                                                        sl = 0;
+                                        }
+                                } while (!success && sl != r10_bio->read_slot);
+
+                                if (success) {
+                                        /* write it back and re-read */
+                                        while (sl != r10_bio->read_slot) {
+                                                int d;
+                                                if (sl==0)
+                                                        sl = conf->copies;
+                                                sl--;
+                                                d = r10_bio->devs[sl].devnum;
+                                                rdev = conf->mirrors[d].rdev;
+                                                if (rdev &&
+                                                    test_bit(In_sync, &rdev->flags)) {
+                                                        if (sync_page_io(rdev->bdev,
+                                                                         r10_bio->devs[sl].addr +
+                                                                         sect + rdev->data_offset,
+                                                                         s<<9, conf->tmppage, WRITE) == 0 ||
+                                                            sync_page_io(rdev->bdev,
+                                                                         r10_bio->devs[sl].addr +
+                                                                         sect + rdev->data_offset,
+                                                                         s<<9, conf->tmppage, READ) == 0) {
+                                                                /* Well, this device is dead */
+                                                                md_error(mddev, rdev);
+                                                        }
+                                                }
+                                        }
+                                } else {
+                                        /* Cannot read from anywhere -- bye bye array */
+                                        md_error(mddev, conf->mirrors[r10_bio->devs[r10_bio->read_slot].devnum].rdev);
+                                        break;
+                                }
+                                sectors -= s;
+                                sect += s;
+                        }
+
+                        unfreeze_array(conf);
+
                         bio = r10_bio->devs[r10_bio->read_slot].bio;
                         r10_bio->devs[r10_bio->read_slot].bio = NULL;
                         bio_put(bio);
@@ -1793,22 +1887,24 @@ static int run(mddev_t *mddev)
          * bookkeeping area. [whatever we allocate in run(),
          * should be freed in stop()]
          */
-        conf = kmalloc(sizeof(conf_t), GFP_KERNEL);
+        conf = kzalloc(sizeof(conf_t), GFP_KERNEL);
         mddev->private = conf;
         if (!conf) {
                 printk(KERN_ERR "raid10: couldn't allocate memory for %s\n",
                         mdname(mddev));
                 goto out;
         }
-        memset(conf, 0, sizeof(*conf));
-        conf->mirrors = kmalloc(sizeof(struct mirror_info)*mddev->raid_disks,
+        conf->mirrors = kzalloc(sizeof(struct mirror_info)*mddev->raid_disks,
                                  GFP_KERNEL);
         if (!conf->mirrors) {
                 printk(KERN_ERR "raid10: couldn't allocate memory for %s\n",
                        mdname(mddev));
                 goto out_free_conf;
         }
-        memset(conf->mirrors, 0, sizeof(struct mirror_info)*mddev->raid_disks);
+
+        conf->tmppage = alloc_page(GFP_KERNEL);
+        if (!conf->tmppage)
+                goto out_free_conf;
 
         conf->near_copies = nc;
         conf->far_copies = fc;
@@ -1918,6 +2014,7 @@ static int run(mddev_t *mddev)
 out_free_conf:
         if (conf->r10bio_pool)
                 mempool_destroy(conf->r10bio_pool);
+        put_page(conf->tmppage);
         kfree(conf->mirrors);
         kfree(conf);
         mddev->private = NULL;