[PATCHSET v13.4 8/9] xfs: reduce iget overhead in scrub

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Hi all,

This patchset looks to reduce iget overhead in two ways: First, a
previous patch conditionally set DONTCACHE on inodes during xchk_irele
on the grounds that we knew better at irele time if an inode should be
dropped.  Unfortunately, over time that patch morphed into a call to
d_mark_dontcache, which resulted in inodes being dropped even if they
were referenced by the dcache.  This actually caused *more* recycle
overhead than if we'd simply called xfs_iget to set DONTCACHE only on

The second patch reduces the cost of untrusted iget for a vectored scrub
call by having the scrubv code maintain a separate refcount to the inode
so that the cache will always hit.

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.


kernel git tree:
Commits in this patchset:
 * xfs: use dontcache for grabbing inodes during scrub
 * xfs: only iget the file once when doing vectored scrub-by-handle
 fs/xfs/scrub/common.c |   12 +++---------
 fs/xfs/scrub/iscan.c  |   13 +++++++++++--
 fs/xfs/scrub/scrub.c  |   45 +++++++++++++++++++++++++++++++++++++++++++++
 fs/xfs/scrub/scrub.h  |    7 +++++++
 4 files changed, 66 insertions(+), 11 deletions(-)

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