Btrfs: extent_map and data=ordered fixes for space balancing

* Add an EXTENT_BOUNDARY state bit to keep the writepage code
from merging data extents that are in the process of being
relocated.  This allows us to do accounting for them properly.

* The balancing code relocates data extents indepdent of the underlying
inode.  The extent_map code was modified to properly account for
things moving around (invalidating extent_map caches in the inode).

* Don't take the drop_mutex in the create_subvol ioctl.  It isn't
required.

* Fix walking of the ordered extent list to avoid races with sys_unlink

* Change the lock ordering rules.  Transaction start goes outside
the drop_mutex.  This allows btrfs_commit_transaction to directly
drop the relocation trees.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 5 insertions, 4 deletions

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 50aea8cb653a..f9cd40967d04 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -290,7 +290,6 @@ int noinline btrfs_cow_block(struct btrfs_trans_handle *trans,
                     struct extent_buffer **cow_ret, u64 prealloc_dest)
 {
         u64 search_start;
-        u64 header_trans;
         int ret;
 
         if (trans->transaction != root->fs_info->running_transaction) {
@@ -304,9 +303,9 @@ int noinline btrfs_cow_block(struct btrfs_trans_handle *trans,
                 WARN_ON(1);
         }
 
-        header_trans = btrfs_header_generation(buf);
         spin_lock(&root->fs_info->hash_lock);
-        if (header_trans == trans->transid &&
+        if (btrfs_header_generation(buf) == trans->transid &&
+            btrfs_header_owner(buf) == root->root_key.objectid &&
             !btrfs_header_flag(buf, BTRFS_HEADER_FLAG_WRITTEN)) {
                 *cow_ret = buf;
                 spin_unlock(&root->fs_info->hash_lock);
@@ -1300,6 +1299,7 @@ again:
                         /* is a cow on this block not required */
                         spin_lock(&root->fs_info->hash_lock);
                         if (btrfs_header_generation(b) == trans->transid &&
+                            btrfs_header_owner(b) == root->root_key.objectid &&
                             !btrfs_header_flag(b, BTRFS_HEADER_FLAG_WRITTEN)) {
                                 spin_unlock(&root->fs_info->hash_lock);
                                 goto cow_done;
@@ -1396,7 +1396,8 @@ cow_done:
 
                         /* this is only true while dropping a snapshot */
                         if (level == lowest_level) {
-                                break;
+                                ret = 0;
+                                goto done;
                         }
 
                         blocknr = btrfs_node_blockptr(b, slot);