Messages in this thread | | | Subject | Re: [PATCH] btrfs: always write superblocks synchronously | From | Chris Mason <> | Date | Wed, 3 May 2017 10:55:44 -0400 |
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On 05/03/2017 04:36 AM, Jan Kara wrote: > On Tue 02-05-17 09:28:13, Davidlohr Bueso wrote: >> Commit b685d3d65ac7 "block: treat REQ_FUA and REQ_PREFLUSH as >> synchronous" removed REQ_SYNC flag from WRITE_FUA implementation. >> Since REQ_FUA and REQ_FLUSH flags are stripped from submitted IO >> when the disk doesn't have volatile write cache and thus effectively >> make the write async. This was seen to cause performance hits up >> to 90% regression in disk IO related benchmarks such as reaim and >> dbench[1]. >> >> Fix the problem by making sure the first superblock write is also >> treated as synchronous since they can block progress of the >> journalling (commit, log syncs) machinery and thus the whole filesystem. >>
>> >> Fixes: b685d3d65ac (block: treat REQ_FUA and REQ_PREFLUSH as synchronous) >> Cc: stable <stable@vger.kernel.org> >> Cc: Jan Kara <jack@suze.cz> >> Signed-off-by: Davidlohr Bueso <dbueso@suse.de> > > I wasn't patient enough and already sent the fix as part of my series > fixing other filesystems [1]. It also fixes one more place in btrfs that > needs REQ_SYNC to return to the original behavior. >
Thanks guys.
-chris
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