From mboxrd@z Thu Jan 1 00:00:00 1970 From: Coly Li Subject: Re: [PATCH] md/raid5: limit request size according to implementation limits Date: Mon, 28 Nov 2016 12:40:15 +0800 Message-ID: References: <148026435214.19980.7956943898609877817.stgit@buzz> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <148026435214.19980.7956943898609877817.stgit@buzz> Sender: linux-raid-owner@vger.kernel.org To: Konstantin Khlebnikov Cc: Shaohua Li , Neil Brown , linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org List-Id: linux-raid.ids On 2016/11/28 上午12:32, Konstantin Khlebnikov wrote: > Current implementation employ 16bit counter of active stripes in lower > bits of bio->bi_phys_segments. If request is big enough to overflow > this counter bio will be completed and freed too early. > > Fortunately this not happens in default configuration because several > other limits prevent that: stripe_cache_size * nr_disks effectively > limits count of active stripes. And small max_sectors_kb at lower > disks prevent that during normal read/write operations. > > Overflow easily happens in discard if it's enabled by module parameter > "devices_handle_discard_safely" and stripe_cache_size is set big enough. > > This patch limits requests size with 256Mb - 8Kb to prevent overflows. > > Signed-off-by: Konstantin Khlebnikov > Cc: Shaohua Li > Cc: Neil Brown > Cc: stable@vger.kernel.org > --- > drivers/md/raid5.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c > index 92ac251e91e6..cce6057b9aca 100644 > --- a/drivers/md/raid5.c > +++ b/drivers/md/raid5.c > @@ -6984,6 +6984,15 @@ static int raid5_run(struct mddev *mddev) > stripe = (stripe | (stripe-1)) + 1; > mddev->queue->limits.discard_alignment = stripe; > mddev->queue->limits.discard_granularity = stripe; > + > + /* > + * We use 16-bit counter of active stripes in bi_phys_segments > + * (minus one for over-loaded initialization) > + */ > + blk_queue_max_hw_sectors(mddev->queue, 0xfffe * STRIPE_SECTORS); > + blk_queue_max_discard_sectors(mddev->queue, > + 0xfffe * STRIPE_SECTORS); > + Could you please to explain why use 0xfffe * STRIPE_SECTORS here ? Thanks. Coly