From c907940bf9f12a55d64f97f9f9ab1ca9224725e7 Mon Sep 17 00:00:00 2001 From: Bruce Evans Date: Sat, 22 Dec 2018 22:59:11 +0000 Subject: [PATCH] Fix devstat on md devices, second attempt. r341765 depends on g_io_deliver() finishing initialization of the bio, but g_io_deliver() actually destroys the bio. INVARIANTS makes the bug obvious by overwriting the bio with garbage. Restore the old order for calling devstat (except don't restore not calling it for the error case), and translate to the devstat KPI so that this order works. Reviewed by: kib --- sys/dev/md/md.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/sys/dev/md/md.c b/sys/dev/md/md.c index b2f6f912fa6..f138bad5cc5 100644 --- a/sys/dev/md/md.c +++ b/sys/dev/md/md.c @@ -1241,12 +1241,22 @@ md_kthread(void *arg) error = sc->start(sc, bp); } + if (bp->bio_cmd == BIO_READ || bp->bio_cmd == BIO_WRITE) { + /* + * Devstat uses (bio_bcount, bio_resid) for + * determining the length of the completed part of + * the i/o. g_io_deliver() will translate from + * bio_completed to that, but it also destroys the + * bio so we must do our own translation. + */ + bp->bio_bcount = bp->bio_length; + bp->bio_resid = (error == -1 ? bp->bio_bcount : 0); + devstat_end_transaction_bio(sc->devstat, bp); + } if (error != -1) { bp->bio_completed = bp->bio_length; g_io_deliver(bp, error); } - if (bp->bio_cmd == BIO_READ || bp->bio_cmd == BIO_WRITE) - devstat_end_transaction_bio(sc->devstat, bp); } }