From: Ulf Hansson <ulf.hansson@linaro.org> To: Christoph Hellwig <hch@lst.de> Cc: Stefan Hajnoczi <stefanha@redhat.com>, Yury Kamenev <damtev@yandex-team.ru>, Jens Axboe <axboe@kernel.dk>, mst@redhat.com, linux-mmc <linux-mmc@vger.kernel.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, virtualization@lists.linux-foundation.org, linux-block <linux-block@vger.kernel.org>, pbonzini@redhat.com, Lauri Kasanen <cand@gmx.com> Subject: Re: [PATCH 1/1] virtio: disable partitions scanning for no partitions block Date: Mon, 24 May 2021 18:25:24 +0200 [thread overview] Message-ID: <CAPDyKFpHeiyLxU1H_gZuxivkiZCKhZ_igsbx_TxSWzUhyaEufQ@mail.gmail.com> (raw) In-Reply-To: <20210524145654.GA2632@lst.de> On Mon, 24 May 2021 at 16:57, Christoph Hellwig <hch@lst.de> wrote: > > On Mon, May 24, 2021 at 03:29:22PM +0100, Stefan Hajnoczi wrote: > > GENHD_FL_NO_PART_SCAN is not used much in other drivers. This makes me > > wonder if the same use case is addressed through other means with SCSI, > > NVMe, etc devices. Maybe Christoph or Jens can weigh in on whether > > adding a bit to disable partition scanning for a virtio-blk fits into > > the big picture? > > > > Is your goal to avoid accidentally detecting partitions because it's > > confusing when that happens? > > I'm really confused what the use case is here. GENHD_FL_NO_PART_SCAN > has four users: > > - the block core setting it for hidden devices, for which the concept > of paritions doesn't make sense. Looking back this should have never > used GENHD_FL_NO_PART_SCAN, and instead the partition scanning code > should just check GENHD_FL_HIDDEN as well. > - mmc uses it for boot partitions and rpmb. I'm not even sure how > these can be exposed as block devices as they don't require block > granularity access IIRC, but if the allow block layer access there > is no reason to ever set these flags. For RPMB, we have converted them into char devices, thus GENHD_FL_NO_PART_SCAN is never set for them. The code needs a cleanup to clarify this. When it comes to eMMC boot partitions, those can be read/written to as any other block device. Although, it's unlikely that they need partitions as they are usually very small, 512Kb or 2MB in that ballpark. At least, that was the thinking behind it when we added GENHD_FL_NO_PART_SCAN for them. If you want to drop GENHD_FL_NO_PART_SCAN for eMMC boot partitions, I don't think it will be an issue. > - loop is a bit of a mess. IIRC the story is that originally the > loop device did not support partitions, then in 2008 support for > partitions was added by partitioning the minor number space, and > then in 2011 support for partitions without that parameter was > added using a new flag in the loop device creation ioctl that uses > the extended dev_t space added since. But even that might be > something we can handled without that flag without breaking the > userspace ABI > - m64card sets it for no good reason at all > > In other words: in a perfect would GENHD_FL_NO_PART_SCAN would not > exist, and it certainly should not be added to a new driver, never > mind a protocol. > _______________________________________________ > Virtualization mailing list > Virtualization@lists.linux-foundation.org > https://lists.linuxfoundation.org/mailman/listinfo/virtualization Kind regards Uffe
WARNING: multiple messages have this Message-ID (diff)
From: Ulf Hansson <ulf.hansson@linaro.org> To: Christoph Hellwig <hch@lst.de> Cc: Yury Kamenev <damtev@yandex-team.ru>, Jens Axboe <axboe@kernel.dk>, mst@redhat.com, linux-mmc <linux-mmc@vger.kernel.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, virtualization@lists.linux-foundation.org, linux-block <linux-block@vger.kernel.org>, Stefan Hajnoczi <stefanha@redhat.com>, pbonzini@redhat.com, Lauri Kasanen <cand@gmx.com> Subject: Re: [PATCH 1/1] virtio: disable partitions scanning for no partitions block Date: Mon, 24 May 2021 18:25:24 +0200 [thread overview] Message-ID: <CAPDyKFpHeiyLxU1H_gZuxivkiZCKhZ_igsbx_TxSWzUhyaEufQ@mail.gmail.com> (raw) In-Reply-To: <20210524145654.GA2632@lst.de> On Mon, 24 May 2021 at 16:57, Christoph Hellwig <hch@lst.de> wrote: > > On Mon, May 24, 2021 at 03:29:22PM +0100, Stefan Hajnoczi wrote: > > GENHD_FL_NO_PART_SCAN is not used much in other drivers. This makes me > > wonder if the same use case is addressed through other means with SCSI, > > NVMe, etc devices. Maybe Christoph or Jens can weigh in on whether > > adding a bit to disable partition scanning for a virtio-blk fits into > > the big picture? > > > > Is your goal to avoid accidentally detecting partitions because it's > > confusing when that happens? > > I'm really confused what the use case is here. GENHD_FL_NO_PART_SCAN > has four users: > > - the block core setting it for hidden devices, for which the concept > of paritions doesn't make sense. Looking back this should have never > used GENHD_FL_NO_PART_SCAN, and instead the partition scanning code > should just check GENHD_FL_HIDDEN as well. > - mmc uses it for boot partitions and rpmb. I'm not even sure how > these can be exposed as block devices as they don't require block > granularity access IIRC, but if the allow block layer access there > is no reason to ever set these flags. For RPMB, we have converted them into char devices, thus GENHD_FL_NO_PART_SCAN is never set for them. The code needs a cleanup to clarify this. When it comes to eMMC boot partitions, those can be read/written to as any other block device. Although, it's unlikely that they need partitions as they are usually very small, 512Kb or 2MB in that ballpark. At least, that was the thinking behind it when we added GENHD_FL_NO_PART_SCAN for them. If you want to drop GENHD_FL_NO_PART_SCAN for eMMC boot partitions, I don't think it will be an issue. > - loop is a bit of a mess. IIRC the story is that originally the > loop device did not support partitions, then in 2008 support for > partitions was added by partitioning the minor number space, and > then in 2011 support for partitions without that parameter was > added using a new flag in the loop device creation ioctl that uses > the extended dev_t space added since. But even that might be > something we can handled without that flag without breaking the > userspace ABI > - m64card sets it for no good reason at all > > In other words: in a perfect would GENHD_FL_NO_PART_SCAN would not > exist, and it certainly should not be added to a new driver, never > mind a protocol. > _______________________________________________ > Virtualization mailing list > Virtualization@lists.linux-foundation.org > https://lists.linuxfoundation.org/mailman/listinfo/virtualization Kind regards Uffe _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization
next prev parent reply other threads:[~2021-05-24 16:26 UTC|newest] Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-05-20 13:39 [PATCH 0/1] virtio: disable partitions scanning for no partitions block Yury Kamenev 2021-05-20 13:39 ` [PATCH 1/1] " Yury Kamenev 2021-05-24 14:29 ` Stefan Hajnoczi 2021-05-24 14:29 ` Stefan Hajnoczi 2021-05-24 14:56 ` Christoph Hellwig 2021-05-24 14:56 ` Christoph Hellwig 2021-05-24 16:25 ` Ulf Hansson [this message] 2021-05-24 16:25 ` Ulf Hansson [not found] ` <90021621883891@mail.yandex-team.ru> 2021-05-24 19:41 ` Paolo Bonzini 2021-05-24 19:41 ` Paolo Bonzini 2021-05-25 12:00 ` Iurii Kamenev -- strict thread matches above, loose matches on Subject: below -- 2021-07-15 9:47 [PATCH 0/1] " Yury Kamenev 2021-07-15 9:47 ` [PATCH 1/1] " Yury Kamenev 2021-07-15 11:22 ` Paolo Bonzini 2021-07-15 11:22 ` Paolo Bonzini 2021-07-16 1:09 ` kernel test robot 2021-07-16 1:09 ` kernel test robot 2021-07-16 1:09 ` kernel test robot 2021-07-16 2:57 ` Jason Wang 2021-07-16 2:57 ` Jason Wang 2021-05-20 13:36 [PATCH 0/1] " Yury Kamenev 2021-05-20 13:36 ` [PATCH 1/1] " Yury Kamenev
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=CAPDyKFpHeiyLxU1H_gZuxivkiZCKhZ_igsbx_TxSWzUhyaEufQ@mail.gmail.com \ --to=ulf.hansson@linaro.org \ --cc=axboe@kernel.dk \ --cc=cand@gmx.com \ --cc=damtev@yandex-team.ru \ --cc=hch@lst.de \ --cc=linux-block@vger.kernel.org \ --cc=linux-kernel@vger.kernel.org \ --cc=linux-mmc@vger.kernel.org \ --cc=mst@redhat.com \ --cc=pbonzini@redhat.com \ --cc=stefanha@redhat.com \ --cc=virtualization@lists.linux-foundation.org \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes, see mirroring instructions on how to clone and mirror all data and code used by this external index.