Btrfs: don't count I/O statistic read errors for missing devices

It is normal behaviour of the low level btrfs function btrfs_map_bio()
to complete a bio with -EIO if the device is missing, instead of just
preventing the bio creation in an earlier step.
This used to cause I/O statistic read error increments and annoying
printk_ratelimited messages. This commit fixes the issue.

Signed-off-by: Stefan Behrens <sbehrens@giantdisaster.de>
Reported-by: Carey Underwood <cwillu@cwillu.com>

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 8a3d259..3f292cf 100644 (file)
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -4061,16 +4061,18 @@ static void btrfs_end_bio(struct bio *bio, int err)
 
                        BUG_ON(stripe_index >= bbio->num_stripes);
                        dev = bbio->stripes[stripe_index].dev;
-                       if (bio->bi_rw & WRITE)
-                               btrfs_dev_stat_inc(dev,
-                                                  BTRFS_DEV_STAT_WRITE_ERRS);
-                       else
-                               btrfs_dev_stat_inc(dev,
-                                                  BTRFS_DEV_STAT_READ_ERRS);
-                       if ((bio->bi_rw & WRITE_FLUSH) == WRITE_FLUSH)
-                               btrfs_dev_stat_inc(dev,
-                                                  BTRFS_DEV_STAT_FLUSH_ERRS);
-                       btrfs_dev_stat_print_on_error(dev);
+                       if (dev->bdev) {
+                               if (bio->bi_rw & WRITE)
+                                       btrfs_dev_stat_inc(dev,
+                                               BTRFS_DEV_STAT_WRITE_ERRS);
+                               else
+                                       btrfs_dev_stat_inc(dev,
+                                               BTRFS_DEV_STAT_READ_ERRS);
+                               if ((bio->bi_rw & WRITE_FLUSH) == WRITE_FLUSH)
+                                       btrfs_dev_stat_inc(dev,
+                                               BTRFS_DEV_STAT_FLUSH_ERRS);
+                               btrfs_dev_stat_print_on_error(dev);
+                       }
                }
        }