tree 106d8e934c1c930d4fae822c76ff18d493492729
parent 3469a32a1e948c54204b5dd6f7476a7d11349e9e
author Theodore Ts'o <tytso@mit.edu> 1394326276 -0500
committer Theodore Ts'o <tytso@mit.edu> 1394326276 -0500

jbd2: calculate statistics without holding j_state_lock and j_list_lock

The two hottest locks, and thus the biggest scalability bottlenecks,
in the jbd2 layer, are the j_list_lock and j_state_lock.  This has
inspired some people to do some truly unnatural things[1].

[1] https://www.usenix.org/system/files/conference/fast14/fast14-paper_kang.pdf

We don't need to be holding both j_state_lock and j_list_lock while
calculating the journal statistics, so move those calculations to the
very end of jbd2_journal_commit_transaction.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>