[PATCH 0/2] Refactor snapshot vs nocow writers locking

[Nikolay Borisov <nborisov@suse.com>]

This patchset first factors out the open code which essentially implements a 
lock that allows to have either multiple reader or multiple writers but not 
both. Then patch 2 just converts the code to using the newly introduced lock. 

The individual patch descriptions contain more information about the technical 
details and invariants that the lock provide. 

I have also CC'ed a copule of the maintainer of linux memory model since my 
patches just factor out the code and I would really like someone proficient 
enough in the usage/semantics of memory barries to review it as well. 

Nikolay Borisov (2):
  btrfs: Implement DRW lock
  btrfs: convert snapshot/nocow exlcusion to drw lock

 fs/btrfs/Makefile      |  2 +-
 fs/btrfs/ctree.h       | 10 ++----
 fs/btrfs/disk-io.c     | 39 ++---------------------
 fs/btrfs/drw_lock.c    | 71 ++++++++++++++++++++++++++++++++++++++++++
 fs/btrfs/drw_lock.h    | 23 ++++++++++++++
 fs/btrfs/extent-tree.c | 35 ---------------------
 fs/btrfs/file.c        | 12 +++----
 fs/btrfs/inode.c       |  8 ++---
 fs/btrfs/ioctl.c       | 10 ++----
 9 files changed, 114 insertions(+), 96 deletions(-)
 create mode 100644 fs/btrfs/drw_lock.c
 create mode 100644 fs/btrfs/drw_lock.h

-- 
2.17.1