Re: [PATCH v4 0/9] Btrfs: free space B-tree

[Omar Sandoval <osandov@osandov.com>]

On Tue, Sep 29, 2015 at 08:50:29PM -0700, Omar Sandoval wrote:
> Hi,
> 
> Here's one more reroll of the free space B-tree patches, a more scalable
> alternative to the free space cache. Minimal changes this time around, I
> mainly wanted to resend this after Holger and I cleared up his bug
> report here: http://www.spinics.net/lists/linux-btrfs/msg47165.html. It
> initially looked like it was a bug in a patch that Josef sent, then in
> this series, but finally Holger and I figured out that it was something
> else in the queue of patches he carries around, we just don't know what
> yet (I'm in the middle of looking into it).

Okay, I tracked down Holger's bug to a bad merge in his patch queue, so
we're off the hook.

> While trying to reproduce
> that bug, I ran xfstests about a trillion times and a bunch of stress
> tests, so this is fairly well tested now. Additionally, the last time
> around, Holger and Austin both bravely offered their Tested-bys on the
> series. I wasn't sure which patch(es) to tack them onto so here they
> are:
> 
> Tested-by: Holger Hoffstätte <holger.hoffstaette@googlemail.com>
> Tested-by: Austin S. Hemmelgarn <ahferroin7@gmail.com>
> 
> Thanks, everyone!
> 
> Omar
> 
> Changes from v3->v4:
> 
> - Added a missing btrfs_end_transaction() to btrfs_create_free_space_tree() and
>   btrfs_clear_free_space_tree() in the error cases after we abort the
>   transaction (see http://www.spinics.net/lists/linux-btrfs/msg47545.html)
> - Rebased the kernel patches on v4.3-rc3
> - Rebased the progs patches on v4.2.1
> 
> v3: http://www.spinics.net/lists/linux-btrfs/msg47095.html
> 
> Changes from v2->v3:
> 
> - Fixed a warning in the free space tree sanity tests caught by Zhao Lei.
> - Moved the addition of a block group to the free space tree to occur either on
>   the first attempt to modify the free space for the block group or in
>   btrfs_create_pending_block_groups(), whichever happens first. This avoids a
>   deadlock (lock recursion) when modifying the free space tree requires
>   allocating a new block group. In order to do this, it was simpler to change
>   the on-disk semantics: the superblock stripes will now appear to be free space
>   according to the free space tree, but load_free_space_tree() will still
>   exclude them when building the in-memory free space cache.
> - Changed the free_space_tree option to space_cache=v2 and made clear_cache
>   clear the free space tree. If the free space tree has been created,
>   the mount will fail unless space_cache=v2 or nospace_cache,clear_cache
>   is given because we cannot allow the free space tree to get out of
>   date.
> - Did a once-over of the code and caught a couple of error handling typos.
> 
> v2: http://www.spinics.net/lists/linux-btrfs/msg46796.html
> 
> Changes from v1->v2:
> 
> - Cleaned up a bunch of unnecessary instances of "if (ret) goto out; ret = 0"
> - Added aborts in the free space tree code closer to the site the error is
>   encountered: where we add or remove block groups, add or remove free space,
>   and also when we convert formats
> - Moved loading of the free space tree into caching_thread() and added a new
>   patch 3 in preparation for it
> - Commented a bunch of stuff in the extent buffer bitmap operations and
>   refactored some of the complicated logic
> 
> v1: http://www.spinics.net/lists/linux-btrfs/msg46713.html
> 
> Omar Sandoval (9):
>   Btrfs: add extent buffer bitmap operations
>   Btrfs: add extent buffer bitmap sanity tests
>   Btrfs: add helpers for read-only compat bits
>   Btrfs: refactor caching_thread()
>   Btrfs: introduce the free space B-tree on-disk format
>   Btrfs: implement the free space B-tree
>   Btrfs: add free space tree sanity tests
>   Btrfs: wire up the free space tree to the extent tree
>   Btrfs: add free space tree mount option
> 
>  fs/btrfs/Makefile                      |    5 +-
>  fs/btrfs/ctree.h                       |  157 +++-
>  fs/btrfs/disk-io.c                     |   38 +
>  fs/btrfs/extent-tree.c                 |   98 +-
>  fs/btrfs/extent_io.c                   |  183 +++-
>  fs/btrfs/extent_io.h                   |   10 +-
>  fs/btrfs/free-space-tree.c             | 1584 ++++++++++++++++++++++++++++++++
>  fs/btrfs/free-space-tree.h             |   72 ++
>  fs/btrfs/super.c                       |   56 +-
>  fs/btrfs/tests/btrfs-tests.c           |   52 ++
>  fs/btrfs/tests/btrfs-tests.h           |   10 +
>  fs/btrfs/tests/extent-io-tests.c       |  138 ++-
>  fs/btrfs/tests/free-space-tests.c      |   35 +-
>  fs/btrfs/tests/free-space-tree-tests.c |  571 ++++++++++++
>  fs/btrfs/tests/qgroup-tests.c          |   20 +-
>  include/trace/events/btrfs.h           |    3 +-
>  16 files changed, 2925 insertions(+), 107 deletions(-)
>  create mode 100644 fs/btrfs/free-space-tree.c
>  create mode 100644 fs/btrfs/free-space-tree.h
>  create mode 100644 fs/btrfs/tests/free-space-tree-tests.c
> 
> -- 
> 2.6.0
> 

-- 
Omar