linux-kernel - Re: [PATCH] bdi: Fix another oops in wb

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Date:   Wed, 13 Jun 2018 16:46:06 +0200
From:   Jan Kara <jack@...e.cz>
To:     Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc:     Jan Kara <jack@...e.cz>, Tejun Heo <tj@...nel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Jens Axboe <axboe@...nel.dk>,
        syzbot <syzbot+4a7438e774b21ddd8eca@...kaller.appspotmail.com>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Dave Chinner <david@...morbit.com>,
        linux-block@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH] bdi: Fix another oops in wb_workfn()

On Wed 13-06-18 19:43:47, Tetsuo Handa wrote:
> Can't we utilize RCU grace period (like shown below) ?

Honestly, the variant 1 looks too ugly to me. However variant 2 looks
mostly OK. We can also avoid the schedule_timeout_uninterruptible(HZ / 10)
from your patch by careful handling of the bit waitqueues. Also I'd avoid
the addition argument to wb_writeback() and split the function instead. The
patch resulting from your and mine ideas is attached. Thoughts?

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR

View attachment "0001-bdi-Fix-another-oops-in-wb_workfn.patch" of type "text/x-patch" (5899 bytes)