On 03/28/2017 11:19 PM, David Sterba wrote:
On Mon, Mar 13, 2017 at 03:42:11PM +0800, Anand Jain wrote:
REQ_PREFLUSH bio to flush dev cache uses btrfs_end_empty_barrier()
completion callback only, as of now, and there it accounts for dev
stat flush errors BTRFS_DEV_STAT_FLUSH_ERRS, so remove it from the
btrfs_end_bio().
Can you please be more specific? I was trying to find the code path that
does the supposedly duplicate accounting for BTRFS_DEV_STAT_FLUSH_ERRS,
but still not there after half an hour.
submit_stripe_bio
btrfsic_submit_bio
btrfs_end_bio
-> stats accounting
write_dev_flush
btrfsic_submit_bio
btrfs_end_empty_barrier
complete
now here it wakes up flush_wait, that is only waited for in
write_dev_flush, there the FLUSH_ERRS accounting happens, but ... I'm
not sure if I haven't lost in the bio handling maze.
As I am checking again, we aren't using REQ_PREFLUSH flag for
any other bio and would suffice for its correctness IMO.
Thanks, Anand
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