btrfs_device fixes

Hello,

This patch series does two things:

- adds allocation helpers for struct btrfs_device and struct btrfs_fs_devices so that all the list_heads, spinlocks, etc are properly initialized and the code for that is in one place;

- fixes a bug in the umount sequence, which, under certain conditions, can lead to mount failures.

This is on top of 3.11-rc3, but applies cleanly to btrfs-next/master as of now. You can pull from:

git://github.com/idryomov/btrfs-unstable.git dev-fixes

Thanks,

Ilya

Ilya Dryomov (4):
Btrfs: find_next_devid: root -> fs_info
Btrfs: add btrfs_alloc_device and switch to it
Btrfs: add alloc_fs_devices and switch to it
Btrfs: rollback btrfs_device fields on umount

 fs/btrfs/volumes.c |  250 +++++++++++++++++++++++++++++++++-------------------
 fs/btrfs/volumes.h |    3 +
 2 files changed, 162 insertions(+), 91 deletions(-)

1.7.10.4