[PATCHSET v29.4 05/13] xfs: online repair of realtime summaries

["Darrick J. Wong" <djwong@kernel.org>]

Hi all,

We now have all the infrastructure we need to repair file metadata.
We'll begin with the realtime summary file, because it is the least
complex data structure.  To support this we need to add three more
pieces to the temporary file code from the previous patchset --
preallocating space in the temp file, formatting metadata into that
space and writing the blocks to disk, and swapping the fork mappings
atomically.

After that, the actual reconstruction of the realtime summary
information is pretty simple, since we can simply write the incore
copy computed by the rtsummary scrubber to the temporary file, swap the
contents, and reap the old blocks.

If you're going to start using this code, I strongly recommend pulling
from my git trees, which are linked below.

This has been running on the djcloud for months with no problems.  Enjoy!
Comments and questions are, as always, welcome.

--D

kernel git tree:
https://git.kernel.org/cgit/linux/kernel/git/djwong/xfs-linux.git/log/?h=repair-rtsummary

xfsprogs git tree:
https://git.kernel.org/cgit/linux/kernel/git/djwong/xfsprogs-dev.git/log/?h=repair-rtsummary

fstests git tree:
https://git.kernel.org/cgit/linux/kernel/git/djwong/xfstests-dev.git/log/?h=repair-rtsummary
---
Commits in this patchset:
 * xfs: support preallocating and copying content into temporary files
 * xfs: teach the tempfile to set up atomic file content exchanges
 * xfs: online repair of realtime summaries
---
 fs/xfs/Makefile                 |    1 
 fs/xfs/scrub/common.c           |    1 
 fs/xfs/scrub/repair.h           |    3 
 fs/xfs/scrub/rtsummary.c        |   33 ++-
 fs/xfs/scrub/rtsummary.h        |   37 ++++
 fs/xfs/scrub/rtsummary_repair.c |  177 ++++++++++++++++++
 fs/xfs/scrub/scrub.c            |   11 +
 fs/xfs/scrub/scrub.h            |    7 +
 fs/xfs/scrub/tempexch.h         |   21 ++
 fs/xfs/scrub/tempfile.c         |  391 +++++++++++++++++++++++++++++++++++++++
 fs/xfs/scrub/tempfile.h         |   15 +
 fs/xfs/scrub/trace.h            |   40 ++++
 12 files changed, 718 insertions(+), 19 deletions(-)
 create mode 100644 fs/xfs/scrub/rtsummary.h
 create mode 100644 fs/xfs/scrub/rtsummary_repair.c
 create mode 100644 fs/xfs/scrub/tempexch.h