From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jens Axboe Subject: Re: [PATCH] scsi: sd: fix entropy gathering for most rotational disks Date: Tue, 12 Feb 2019 09:06:29 -0700 Message-ID: References: <1549987525.3173.17.camel@HansenPartnership.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1549987525.3173.17.camel@HansenPartnership.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: James Bottomley , linux-scsi Cc: Xuewei Zhang , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, Mikael Pettersson List-Id: linux-scsi@vger.kernel.org On 2/12/19 9:05 AM, James Bottomley wrote: > The problem is that the default for MQ is not to gather entropy, > whereas the default for the legacy queue was always to gather it. The > original attempt to fix entropy gathering for rotational disks under MQ > added an else branch in sd_read_block_characteristics(). > Unfortunately, the entire check isn't reached if the device has no > characteristics VPD page. Since this page was only introduced in SBC-3 > and its optional anyway, most less expensive rotational disks don't > have one, meaning they all stopped gathering entropy when we made MQ > the default. In a wholly unrelated change, openssl and openssh won't > function until the random number generator is initialised, meaning lots > of people have been seeing large delays before they could log into > systems with default MQ kernels due to this lack of entropy, because it > now can take tens of minutes to initialise the kernel random number > generator. > > The fix is to set the non-rotational and add-randomness flags > unconditionally early on in the disk initialization path, so they can > be reset only if the device actually reports being non-rotational via > the VPD page. Reviewed-by: Jens Axboe -- Jens Axboe