[PATCH v10 00/12] timekeeping/fs: multigrain timestamp redux

[Jeff Layton]

This is a replacement for the v6 series sitting in Christian's
vfs.mgtime branch. The main changes here are to the changelogs,
documentation and comments. I've also moved the timekeeping patches to
the front of the series, and done some minor cleanups.

The pipe1_threads test shows these averages on my test rig with this
series:

    v6.11:				89233600 (baseline)
    v6.11 + v9 series:			88460897 (<1% slower)

Thanks for all of the review so far!

Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
---
Changes in v10:
- Reorder timekeeping patches to front of series
- Better separate timekeeping and fs changes
- add data_race annotations to per_cpu fetches
- get rid of pointless test for unsigned long to go negative
- better spacing for declarations and definitions in timekeeping_internal.h
- minor style cleanups
- Link to v9: https://lore.kernel.org/r/20241002-mgtime-v9-0-77e2baad57ac@xxxxxxxxxx

Changes in v9:
- Comment and documentation cleanups.
- Drop the EXPORT_SYMBOL_GPL() from new timekeeper interfaces
- Link to v8: https://lore.kernel.org/r/20241001-mgtime-v8-0-903343d91bc3@xxxxxxxxxx

Changes in v8:
- split patch that adds percpu counters into fs and timekeeping patches
- convert percpu counters to unsigned longs
- directly access the offs_real value in timekeeper instead of going
  through offsets array
- drop WARN_ON's in timekeeping patches
- better changelogs and more comments for the timekeeping bits
- better document how backward realtime clock jumps affect things
- Link to v7: https://lore.kernel.org/r/20240913-mgtime-v7-0-92d4020e3b00@xxxxxxxxxx

Changes in v7:
- move the floor value handling into timekeeper for better performance
- Link to v6: https://lore.kernel.org/r/20240715-mgtime-v6-0-48e5d34bd2ba@xxxxxxxxxx

Changes in v6:
- Normalize timespec64 in inode_set_ctime_to_ts
- use DEFINE_PER_CPU counters for better vfs consistency
- skip ctime cmpxchg if the result means nothing will change
- add trace_ctime_xchg_skip to track skipped ctime updates
- use __print_flags in ctime_ns_xchg tracepoint
- Link to v5: https://lore.kernel.org/r/20240711-mgtime-v5-0-37bb5b465feb@xxxxxxxxxx

Changes in v5:
- refetch coarse time in coarse_ctime if not returning floor
- timestamp_truncate before swapping new ctime value into place
- track floor value as atomic64_t
- cleanups to Documentation file
- Link to v4: https://lore.kernel.org/r/20240708-mgtime-v4-0-a0f3c6fb57f3@xxxxxxxxxx

Changes in v4:
- reordered tracepoint fields for better packing
- rework percpu counters again to also count fine grained timestamps
- switch to try_cmpxchg for better efficiency
- Link to v3: https://lore.kernel.org/r/20240705-mgtime-v3-0-85b2daa9b335@xxxxxxxxxx

Changes in v3:
- Drop the conversion of i_ctime fields to ktime_t, and use an unused bit
  of the i_ctime_nsec field as QUERIED flag.
- Better tracepoints for tracking floor and ctime updates
- Reworked percpu counters to be more useful
- Track floor as monotonic value, which eliminates clock-jump problem

Changes in v2:
- Added Documentation file
- Link to v1: https://lore.kernel.org/r/20240626-mgtime-v1-0-a189352d0f8f@xxxxxxxxxx

---
Jeff Layton (12):
      timekeeping: add interfaces for handling timestamps with a floor value
      timekeeping: add percpu counter for tracking floor swap events
      fs: add infrastructure for multigrain timestamps
      fs: have setattr_copy handle multigrain timestamps appropriately
      fs: handle delegated timestamps in setattr_copy_mgtime
      fs: tracepoints around multigrain timestamp events
      fs: add percpu counters for significant multigrain timestamp events
      Documentation: add a new file documenting multigrain timestamps
      xfs: switch to multigrain timestamps
      ext4: switch to multigrain timestamps
      btrfs: convert to multigrain timestamps
      tmpfs: add support for multigrain timestamps

 Documentation/filesystems/index.rst         |   1 +
 Documentation/filesystems/multigrain-ts.rst | 125 ++++++++++++
 fs/attr.c                                   |  60 +++++-
 fs/btrfs/file.c                             |  25 +--
 fs/btrfs/super.c                            |   3 +-
 fs/ext4/super.c                             |   2 +-
 fs/inode.c                                  | 282 +++++++++++++++++++++++++---
 fs/stat.c                                   |  46 ++++-
 fs/xfs/libxfs/xfs_trans_inode.c             |   6 +-
 fs/xfs/xfs_iops.c                           |  10 +-
 fs/xfs/xfs_super.c                          |   2 +-
 include/linux/fs.h                          |  36 +++-
 include/linux/timekeeping.h                 |   5 +
 include/trace/events/timestamp.h            | 124 ++++++++++++
 kernel/time/timekeeping.c                   | 106 +++++++++++
 kernel/time/timekeeping_debug.c             |  14 ++
 kernel/time/timekeeping_internal.h          |  15 ++
 mm/shmem.c                                  |   2 +-
 18 files changed, 791 insertions(+), 73 deletions(-)
---
base-commit: 98f7e32f20d28ec452afb208f9cffc08448a2652
change-id: 20240913-mgtime-20c98bcda88e

Best regards,
-- 
Jeff Layton <jlayton@xxxxxxxxxx>