[PATCHSET v24.0 0/7] xfs_scrub: move fstrim to a separate phase

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Hi all,

Back when I originally designed xfs_scrub, all filesystem metadata
checks were complete by the end of phase 3, and phase 4 was where all
the metadata repairs occurred.  On the grounds that the filesystem
should be fully consistent by then, I made a call to FITRIM at the end
of phase 4 to discard empty space in the filesystem.

Unfortunately, that's no longer the case -- summary counters, link
counts, and quota counters are not checked until phase 7.  It's not safe
to instruct the storage to unmap "empty" areas if we don't know where
those empty areas are, so we need to create a phase 8 to trim the fs.
While we're at it, make it more obvious that fstrim only gets to run if
there are no unfixed corruptiosn and no other runtime errors have
occurred.

Finally, parallelize the fstrim calls by making them per-AG instead of
per-filesystem.  This cuts down the trimming time considerably on more
modern hardware that can handle (or at least combine) concurrent discard
requests.

If you're going to start using this mess, you probably ought to just
pull from my git trees, which are linked below.

This is an extraordinary way to destroy everything.  Enjoy!
Comments and questions are, as always, welcome.

--D

xfsprogs git tree:
https://git.kernel.org/cgit/linux/kernel/git/djwong/xfsprogs-dev.git/log/?h=scrub-fstrim-phase
---
 scrub/Makefile    |    1 
 scrub/phase4.c    |   30 +----------
 scrub/phase8.c    |  150 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 scrub/vfs.c       |   22 +++++---
 scrub/vfs.h       |    2 -
 scrub/xfs_scrub.c |   11 ++++
 scrub/xfs_scrub.h |    3 +
 7 files changed, 182 insertions(+), 37 deletions(-)
 create mode 100644 scrub/phase8.c




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