On Thu, Nov 10 2016, Shaohua Li wrote: > On Wed, Nov 09, 2016 at 10:21:32AM +1100, Neil Brown wrote: >> bitmap_flush() finishes with bitmap_update_sb(), and that finishes >> with write_page(..., 1), so write_page() will wait for all writes >> to complete. So there is no point calling md_super_wait() >> immediately afterwards. >> >> Signed-off-by: NeilBrown <neilb@xxxxxxxx> >> --- >> drivers/md/md.c | 1 - >> 1 file changed, 1 deletion(-) >> >> diff --git a/drivers/md/md.c b/drivers/md/md.c >> index f389d8abe137..1f1c7f007b68 100644 >> --- a/drivers/md/md.c >> +++ b/drivers/md/md.c >> @@ -5472,7 +5472,6 @@ static void __md_stop_writes(struct mddev *mddev) >> del_timer_sync(&mddev->safemode_timer); >> >> bitmap_flush(mddev); >> - md_super_wait(mddev); > > bitmap_flush() could be null if there is no bitmap, is this safe? Good question. If there is no bitmap, then all metadata updates (both superblock and bad-block-list) are synchronous in md_update_sb(), which is always called under ->reconfig_mutex and so which cannot race with this code. So yes, it is safe. That md_super_wait() was only ever intended to wait for things that bitmap_flush() might have flushed, so it should have been inside that function. Thanks, NeilBrown
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