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From: Bart Van Assche <bvanassche@acm.org>
To: Alexander Potapenko <glider@google.com>,
	Chaitanya Kulkarni <Chaitanya.Kulkarni@wdc.com>,
	Damien Le Moal <damien.lemoal@wdc.com>
Cc: Jens Axboe <axboe@kernel.dk>,
	"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
	Willem de Bruijn <willemb@google.com>,
	Dmitriy Vyukov <dvyukov@google.com>
Subject: Re: null_handle_cmd() doesn't initialize data when reading
Date: Sun, 10 May 2020 09:20:39 -0700	[thread overview]
Message-ID: <277579c9-9e33-89ea-bfcd-bc14a543726c@acm.org> (raw)
In-Reply-To: <CAG_fn=WVHpRQ19MK12pxiizTEvUFLiV7LJgF_LrX_G2SYd=ivQ@mail.gmail.com>

On 2020-05-10 03:03, Alexander Potapenko wrote:
> Thanks for the explanation!
> The code has changed recently, and my patch does not apply anymore,
> yet the problem still persists.
> I ended up just calling null_handle_rq() at the end of
> null_process_cmd(), but we probably need a cleaner fix.

Does this (totally untested) patch help? copy_to_nullb() guarantees that
it will write some data to the pages that it allocates but does not
guarantee yet that all data of the pages it allocates is initialized.

diff --git a/drivers/block/null_blk_main.c b/drivers/block/null_blk_main.c
index 8efd8778e209..06f5761fccb6 100644
--- a/drivers/block/null_blk_main.c
+++ b/drivers/block/null_blk_main.c
@@ -848,7 +848,7 @@ static struct nullb_page *null_insert_page(struct
nullb *nullb,

 	spin_unlock_irq(&nullb->lock);

-	t_page = null_alloc_page(GFP_NOIO);
+	t_page = null_alloc_page(GFP_NOIO | __GFP_ZERO);
 	if (!t_page)
 		goto out_lock;


  reply	other threads:[~2020-05-10 16:20 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-15 10:16 null_handle_cmd() doesn't initialize data when reading Alexander Potapenko
2019-11-20 23:12 ` Jens Axboe
2019-11-22 11:58   ` Alexander Potapenko
2019-11-25  4:01     ` Chaitanya Kulkarni
2020-05-10 10:03       ` Alexander Potapenko
2020-05-10 16:20         ` Bart Van Assche [this message]
2020-05-11 12:58           ` Alexander Potapenko
2020-05-11 13:01             ` Damien Le Moal
2020-05-11 13:09               ` Alexander Potapenko
2020-05-11 23:18             ` Bart Van Assche
2020-05-12  1:25               ` Bart Van Assche
2020-05-12  1:42                 ` Damien Le Moal
2020-05-12  2:43                   ` Bart Van Assche
2020-05-12  3:23                     ` Damien Le Moal

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