[PATCH] md: improve handing of read errors with raid6

This is a simple port of match functionality across from raid5.  If we get a
read error, we don't kick the drive straight away, but try to over-write with
good data first.

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, 66 insertions, 4 deletions

diff --git a/drivers/md/raid6main.c b/drivers/md/raid6main.c
index 52e8796bb8ac..7a51553d8be5 100644
--- a/drivers/md/raid6main.c
+++ b/drivers/md/raid6main.c
@@ -367,8 +367,8 @@ static void shrink_stripes(raid6_conf_t *conf)
         conf->slab_cache = NULL;
 }
 
-static int raid6_end_read_request (struct bio * bi, unsigned int bytes_done,
-                                   int error)
+static int raid6_end_read_request(struct bio * bi, unsigned int bytes_done,
+                                  int error)
 {
         struct stripe_head *sh = bi->bi_private;
         raid6_conf_t *conf = sh->raid_conf;
@@ -420,9 +420,35 @@ static int raid6_end_read_request (struct bio * bi, unsigned int bytes_done,
 #else
                 set_bit(R5_UPTODATE, &sh->dev[i].flags);
 #endif
+                if (test_bit(R5_ReadError, &sh->dev[i].flags)) {
+                        printk(KERN_INFO "raid6: read error corrected!!\n");
+                        clear_bit(R5_ReadError, &sh->dev[i].flags);
+                        clear_bit(R5_ReWrite, &sh->dev[i].flags);
+                }
+                if (atomic_read(&conf->disks[i].rdev->read_errors))
+                        atomic_set(&conf->disks[i].rdev->read_errors, 0);
         } else {
-                md_error(conf->mddev, conf->disks[i].rdev);
+                int retry = 0;
                 clear_bit(R5_UPTODATE, &sh->dev[i].flags);
+                atomic_inc(&conf->disks[i].rdev->read_errors);
+                if (conf->mddev->degraded)
+                        printk(KERN_WARNING "raid6: read error not correctable.\n");
+                else if (test_bit(R5_ReWrite, &sh->dev[i].flags))
+                        /* Oh, no!!! */
+                        printk(KERN_WARNING "raid6: read error NOT corrected!!\n");
+                else if (atomic_read(&conf->disks[i].rdev->read_errors)
+                         > conf->max_nr_stripes)
+                        printk(KERN_WARNING
+                               "raid6: Too many read errors, failing device.\n");
+                else
+                        retry = 1;
+                if (retry)
+                        set_bit(R5_ReadError, &sh->dev[i].flags);
+                else {
+                        clear_bit(R5_ReadError, &sh->dev[i].flags);
+                        clear_bit(R5_ReWrite, &sh->dev[i].flags);
+                        md_error(conf->mddev, conf->disks[i].rdev);
+                }
         }
         rdev_dec_pending(conf->disks[i].rdev, conf->mddev);
 #if 0
@@ -1079,6 +1105,12 @@ static void handle_stripe(struct stripe_head *sh, struct page *tmp_page)
                 if (dev->written) written++;
                 rdev = conf->disks[i].rdev; /* FIXME, should I be looking rdev */
                 if (!rdev || !test_bit(In_sync, &rdev->flags)) {
+                        /* The ReadError flag will just be confusing now */
+                        clear_bit(R5_ReadError, &dev->flags);
+                        clear_bit(R5_ReWrite, &dev->flags);
+                }
+                if (!rdev || !test_bit(In_sync, &rdev->flags)
+                    || test_bit(R5_ReadError, &dev->flags)) {
                         if ( failed < 2 )
                                 failed_num[failed] = i;
                         failed++;
@@ -1095,6 +1127,14 @@ static void handle_stripe(struct stripe_head *sh, struct page *tmp_page)
         if (failed > 2 && to_read+to_write+written) {
                 for (i=disks; i--; ) {
                         int bitmap_end = 0;
+
+                        if (test_bit(R5_ReadError, &sh->dev[i].flags)) {
+                                mdk_rdev_t *rdev = conf->disks[i].rdev;
+                                if (rdev && test_bit(In_sync, &rdev->flags))
+                                        /* multiple read failures in one stripe */
+                                        md_error(conf->mddev, rdev);
+                        }
+
                         spin_lock_irq(&conf->device_lock);
                         /* fail all writes first */
                         bi = sh->dev[i].towrite;
@@ -1130,7 +1170,8 @@ static void handle_stripe(struct stripe_head *sh, struct page *tmp_page)
                         }
 
                         /* fail any reads if this device is non-operational */
-                        if (!test_bit(R5_Insync, &sh->dev[i].flags)) {
+                        if (!test_bit(R5_Insync, &sh->dev[i].flags) ||
+                            test_bit(R5_ReadError, &sh->dev[i].flags)) {
                                 bi = sh->dev[i].toread;
                                 sh->dev[i].toread = NULL;
                                 if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
@@ -1457,6 +1498,27 @@ static void handle_stripe(struct stripe_head *sh, struct page *tmp_page)
                 clear_bit(STRIPE_SYNCING, &sh->state);
         }
 
+        /* If the failed drives are just a ReadError, then we might need
+         * to progress the repair/check process
+         */
+        if (failed <= 2 && ! conf->mddev->ro)
+                for (i=0; i<failed;i++) {
+                        dev = &sh->dev[failed_num[i]];
+                        if (test_bit(R5_ReadError, &dev->flags)
+                            && !test_bit(R5_LOCKED, &dev->flags)
+                            && test_bit(R5_UPTODATE, &dev->flags)
+                                ) {
+                                if (!test_bit(R5_ReWrite, &dev->flags)) {
+                                        set_bit(R5_Wantwrite, &dev->flags);
+                                        set_bit(R5_ReWrite, &dev->flags);
+                                        set_bit(R5_LOCKED, &dev->flags);
+                                } else {
+                                        /* let's read it back */
+                                        set_bit(R5_Wantread, &dev->flags);
+                                        set_bit(R5_LOCKED, &dev->flags);
+                                }
+                        }
+                }
         spin_unlock(&sh->lock);
 
         while ((bi=return_bi)) {