[PATCH] md: improvements to raid5 handling of read errors

Two refinements to the 'attempt-overwrite-on-read-error' mechanism.
1/ If the array is read-only, don't attempt an over-write.
2/ If there are more than max_nr_stripes read errors on a device with
   no success, fail the drive.  This will make sure a dead
   drive will be eventually kicked even when we aren't trying
   to rewrite (which would normally kick a dead drive more quickly.

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

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 3db5c35..3fb8039 100644 (file)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -1582,6 +1582,7 @@ static mdk_rdev_t *md_import_device(dev_t newdev, int super_format, int super_mi
        rdev->in_sync = 0;
        rdev->data_offset = 0;
        atomic_set(&rdev->nr_pending, 0);
+       atomic_set(&rdev->read_errors, 0);
 
        size = rdev->bdev->bd_inode->i_size >> BLOCK_SIZE_BITS;
        if (!size) {

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 08a1620..77610b9 100644 (file)
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -420,21 +420,29 @@ static int raid5_end_read_request(struct bio * bi, unsigned int bytes_done,
                        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 {
+               int retry = 0;
                clear_bit(R5_UPTODATE, &sh->dev[i].flags);
-               if (conf->mddev->degraded) {
+               atomic_inc(&conf->disks[i].rdev->read_errors);
+               if (conf->mddev->degraded)
                        printk("R5: read error not correctable.\n");
-                       clear_bit(R5_ReadError, &sh->dev[i].flags);
-                       clear_bit(R5_ReWrite, &sh->dev[i].flags);
-                       md_error(conf->mddev, conf->disks[i].rdev);
-               } else if (test_bit(R5_ReWrite, &sh->dev[i].flags)) {
+               else if (test_bit(R5_ReWrite, &sh->dev[i].flags))
                        /* Oh, no!!! */
                        printk("R5: read error NOT corrected!!\n");
+               else if (atomic_read(&conf->disks[i].rdev->read_errors)
+                        > conf->max_nr_stripes)
+                       printk("raid5: 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);
-               } else
-                       set_bit(R5_ReadError, &sh->dev[i].flags);
+               }
        }
        rdev_dec_pending(conf->disks[i].rdev, conf->mddev);
 #if 0
@@ -1328,7 +1336,8 @@ static void handle_stripe(struct stripe_head *sh)
        /* If the failed drive is just a ReadError, then we might need to progress
         * the repair/check process
         */
-       if (failed == 1 && test_bit(R5_ReadError, &sh->dev[failed_num].flags)
+       if (failed == 1 && ! conf->mddev->ro &&
+           test_bit(R5_ReadError, &sh->dev[failed_num].flags)
            && !test_bit(R5_LOCKED, &sh->dev[failed_num].flags)
            && test_bit(R5_UPTODATE, &sh->dev[failed_num].flags)
                ) {

diff --git a/include/linux/raid/md_k.h b/include/linux/raid/md_k.h
index 4169c11..200c69e 100644 (file)
--- a/include/linux/raid/md_k.h
+++ b/include/linux/raid/md_k.h
@@ -134,6 +134,9 @@ struct mdk_rdev_s
                                         * only maintained for arrays that
                                         * support hot removal
                                         */
+       atomic_t        read_errors;    /* number of consecutive read errors that
+                                        * we have tried to ignore.
+                                        */
 };
 
 typedef struct mdk_personality_s mdk_personality_t;