btrfs: scrub: set error stats when tree block spanning stripes

It is better to show error stats to user when we found tree block
spanning stripes.

On a btrfs created by old version of btrfs-convert:
Before patch:
  # btrfs scrub start -B /dev/vdh
  scrub done for 8b342d35-2904-41ab-b3cb-2f929709cf47
          scrub started at Tue Aug 25 21:19:09 2015 and finished after 00:00:00
          total bytes scrubbed: 53.54MiB with 0 errors
  # dmesg
  ...
  [  128.711434] BTRFS error (device vdh): scrub: tree block 27054080 spanning stripes, ignored. logical=27000832
  [  128.712744] BTRFS error (device vdh): scrub: tree block 27054080 spanning stripes, ignored. logical=27066368
  ...

After patch:
  # btrfs scrub start -B /dev/vdh
  scrub done for ff7f844b-7a4e-4b1a-88a9-8252ab25be1b
          scrub started at Tue Aug 25 21:42:29 2015 and finished after 00:00:00
          total bytes scrubbed: 53.60MiB with 2 errors
          error details:
          corrected errors: 0, uncorrectable errors: 2, unverified errors: 0
  ERROR: There are uncorrectable errors.
  # dmesg
  ...omit...
  #

Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index 550de89a8661..3e2755eb0f08 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -3012,6 +3012,9 @@ static noinline_for_stack int scrub_raid56_parity(struct scrub_ctx *sctx,
                              logic_start + map->stripe_len)) {
                                 btrfs_err(fs_info, "scrub: tree block %llu spanning stripes, ignored. logical=%llu",
                                           key.objectid, logic_start);
+                                spin_lock(&sctx->stat_lock);
+                                sctx->stat.uncorrectable_errors++;
+                                spin_unlock(&sctx->stat_lock);
                                 goto next;
                         }
 again:
@@ -3361,6 +3364,9 @@ static noinline_for_stack int scrub_stripe(struct scrub_ctx *sctx,
                                            "scrub: tree block %llu spanning "
                                            "stripes, ignored. logical=%llu",
                                        key.objectid, logical);
+                                spin_lock(&sctx->stat_lock);
+                                sctx->stat.uncorrectable_errors++;
+                                spin_unlock(&sctx->stat_lock);
                                 goto next;
                         }