btrfs: scrub

This adds an initial implementation for scrub. It works quite
straightforward. The usermode issues an ioctl for each device in the
fs. For each device, it enumerates the allocated device chunks. For
each chunk, the contained extents are enumerated and the data checksums
fetched. The extents are read sequentially and the checksums verified.
If an error occurs (checksum or EIO), a good copy is searched for. If
one is found, the bad copy will be rewritten.
All enumerations happen from the commit roots. During a transaction
commit, the scrubs get paused and afterwards continue from the new
roots.

This commit is based on the series originally posted to linux-btrfs
with some improvements that resulted from comments from David Sterba,
Ilya Dryomov and Jan Schmidt.

Signed-off-by: Arne Jansen <sensille@gmx.net>

1 files changed, 4 insertions, 2 deletions

diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index f997ec0c1ba4..f1a0726da5f5 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -614,7 +614,7 @@ static noinline int replay_one_extent(struct btrfs_trans_handle *trans,
 
                         ret = btrfs_lookup_csums_range(root->log_root,
                                                 csum_start, csum_end - 1,
-                                                &ordered_sums);
+                                                &ordered_sums, 0);
                         BUG_ON(ret);
                         while (!list_empty(&ordered_sums)) {
                                 struct btrfs_ordered_sum *sums;
@@ -2093,7 +2093,9 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans,
          * the running transaction open, so a full commit can't hop
          * in and cause problems either.
          */
+        btrfs_scrub_pause_super(root);
         write_ctree_super(trans, root->fs_info->tree_root, 1);
+        btrfs_scrub_continue_super(root);
         ret = 0;
 
         mutex_lock(&root->log_mutex);
@@ -2689,7 +2691,7 @@ static noinline int copy_items(struct btrfs_trans_handle *trans,
                                 ret = btrfs_lookup_csums_range(
                                                 log->fs_info->csum_root,
                                                 ds + cs, ds + cs + cl - 1,
-                                                &ordered_sums);
+                                                &ordered_sums, 0);
                                 BUG_ON(ret);
                         }
                 }