On Wed, Mar 30 2016, Shaohua Li wrote: > On Tue, Mar 29, 2016 at 08:22:00AM -0400, Xiao Ni wrote: >> Hi all >> >> I encountered one NULL pointer dereference problem. >> >> The environment： >> latest linux-stable and mdadm codes >> aarch64 platform >> the md device is created with loop devices >> >> It's a test case to check date integrity. I added the test script as the attachment. > > Could you please try this patch: > > > From b86d9e1724184c79ad1ea63901aec802492b861c Mon Sep 17 00:00:00 2001 > Message-Id: <b86d9e1724184c79ad1ea63901aec802492b861c.1459285706.git.shli@xxxxxx> > From: Shaohua Li <shli@xxxxxx> > Date: Tue, 29 Mar 2016 14:00:19 -0700 > Subject: [PATCH] MD: add rdev reference for super write > > md_super_write() and corresponding md_super_wait() generally are called > with reconfig_mutex locked, which prevents disk disappears. There is one > case this rule is broken. write_sb_page of bitmap.c doesn't hold the > mutex. next_active_rdev does increase rdev reference, but it decreases > the reference too early (eg, before IO finish). disk can disappear at > the window. We unconditionally increase rdev reference in > md_super_write() to avoid the race. > Yes, that makes sense. Thanks. Acked-by: NeilBrown <neilb@xxxxxxxx> > Reported-by: Xiao Ni <xni@xxxxxxxxxx> > Cc: Neil Brown <neilb@xxxxxxx> > Signed-off-by: Shaohua Li <shli@xxxxxx> > --- > drivers/md/md.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/md/md.c b/drivers/md/md.c > index c068f17..bcfde333 100644 > --- a/drivers/md/md.c > +++ b/drivers/md/md.c > @@ -718,6 +718,7 @@ static void super_written(struct bio *bio) > > if (atomic_dec_and_test(&mddev->pending_writes)) > wake_up(&mddev->sb_wait); > + rdev_dec_pending(rdev, mddev); > bio_put(bio); > } > > @@ -732,6 +733,8 @@ void md_super_write(struct mddev *mddev, struct md_rdev *rdev, > */ > struct bio *bio = bio_alloc_mddev(GFP_NOIO, 1, mddev); > > + atomic_inc(&rdev->nr_pending); > + > bio->bi_bdev = rdev->meta_bdev ? rdev->meta_bdev : rdev->bdev; > bio->bi_iter.bi_sector = sector; > bio_add_page(bio, page, size, 0); > -- > 2.8.0.rc2 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-raid" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html
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