[PATCH 0/2] btrfs: scrub: update last_physical more frequently

[Qu Wenruo <wqu@suse.com>]

There is a report in the mailling list that scrub only updates its
@last_physical at the end of a chunk.
In fact, it can be worse if there is a used stripe (aka, some extents
exist in the stripe) at the chunk boundary.
As it would skip the @last_physical for that chunk at all.

With @last_physical not update for a long time, if we cancel the scrub
halfway and resume, the resumed one scrub would only start at
@last_physical, meaning a lot of scrubbed extents would be re-scrubbed,
wasting quite some IO and CPU.

This patchset would fix it by updateing @last_physical for each finished
stripe (including both P/Q stripe of RAID56, and all data stripes for
all profiles), so that even if the scrub is cancelled, we at most
re-scrub one stripe.

Qu Wenruo (2):
  btrfs: extract the stripe length calculation into a helper
  btrfs: scrub: update last_physical after scrubing one stripe

 fs/btrfs/scrub.c | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

-- 
2.44.0