Merge git://git.kernel.org/pub/scm/linux/kernel/git/mason/btrfs-unstable

* git://git.kernel.org/pub/scm/linux/kernel/git/mason/btrfs-unstable:
  Btrfs: prevent RAID level downgrades when space is low
  Btrfs: account for missing devices in RAID allocation profiles
  Btrfs: EIO when we fail to read tree roots
  Btrfs: fix compiler warnings
  Btrfs: Make async snapshot ioctl more generic
  Btrfs: pwrite blocked when writing from the mmaped buffer of the same page
  Btrfs: Fix a crash when mounting a subvolume
  Btrfs: fix sync subvol/snapshot creation
  Btrfs: Fix page leak in compressed writeback path
  Btrfs: do not BUG if we fail to remove the orphan item for dead snapshots
  Btrfs: fixup return code for btrfs_del_orphan_item
  Btrfs: do not do fast caching if we are allocating blocks for tree_root
  Btrfs: deal with space cache errors better
  Btrfs: fix use after free in O_DIRECT

diff --cc fs/btrfs/disk-io.c
Simple merge

diff --cc fs/btrfs/extent-tree.c
Simple merge

diff --cc fs/btrfs/inode.c
Simple merge

diff --cc fs/btrfs/super.c
Simple merge

diff --cc fs/btrfs/volumes.c
Simple merge

diff --cc fs/btrfs/volumes.h
index 2b638b6e4eeae7cb9428490a897c1e10a9aaad1f,a668c011698236f223e3fa5071301c35ec01d5e5..2740db49eb04d7a8de03d18e5935a97ff43ef9db
--- 1/fs/btrfs/volumes.h
--- 2/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@@ -42,8 -42,10 +42,9 @@@ struct btrfs_device 
        int running_pending;
        u64 generation;
  
 -      int barriers;
        int writeable;
        int in_fs_metadata;
+       int missing;
  
        spinlock_t io_lock;