Re: [dm-devel] [PATCH 0/2] boot to a mapped device
On Thu, Sep 27 2018 at 12:36pm -0400, Kees Cook wrote: > On Thu, Sep 27, 2018 at 7:23 AM, Mike Snitzer wrote: > > On Wed, Sep 26 2018 at 3:16am -0400, > > Richard Weinberger wrote: > > > >> Helen, > >> > >> On Wed, Sep 26, 2018 at 7:01 AM Helen Koike > >> wrote: > >> > > >> > This series is reviving an old patchwork. > >> > Booting from a mapped device requires an initramfs. This series is > >> > allows for device-mapper targets to be configured at boot time for > >> > use early in the boot process (as the root device or otherwise). > >> > >> What is the reason for this patch series? > >> Setting up non-trivial root filesystems/storage always requires an > >> initramfs, there is nothing > >> wrong about this. > > > > Exactly. If phones or whatever would benefit from this patchset then > > say as much. > > I think some of the context for the series was lost in commit logs, > but yes, both Android and Chrome OS do not use initramfs. The only > thing that was needed to do this was being able to configure dm > devices on the kernel command line, so the overhead of a full > initramfs was seen as a boot time liability, a boot image size > liability (e.g. Chrome OS has a limited amount of storage available > for the boot image that is covered by the static root of trust > signature), and a complexity risk: everything that is needed for boot > could be specified on the kernel command line, so better to avoid the > whole initramfs dance. > > So, instead, this plumbs the dm commands directly instead of bringing > up a full userspace and performing ioctls. > > > I will not accept this patchset at this time. > > > >> > Example, the following could be added in the boot parameters. > >> > dm="lroot,,,rw, 0 4096 linear 98:16 0, 4096 4096 linear 98:32 0" > >> > root=/dev/dm-0 > >> > >> Hmmm, the new dm= parameter is anything but easy to get right. > > > > No, it isn't.. exposes way too much potential for users hanging > > themselves. > > IIRC, the changes in syntax were suggested back when I was trying to > drive this series: > https://www.redhat.com/archives/dm-devel/2016-February/msg00199.html > > And it matches the "concise" format in dmsetup: > https://sourceware.org/git/?p=lvm2.git;a=commit;h=827be01758ec5adb7b9d5ea75b658092adc65534 > > What do you feel are next steps? There is quite a lot of init/ code, to handle parsing the concise DM format, that is being proposed for inclusion. I question why that DM-specific code would be located in init/ There also needs to be a careful comparison done between the proposed init/ code to support consise DM format and the userspace lvm2 equivalent (e.g. lvm2.git commit 827be0175) That aside, the DM targets that are allowed to be supported by this dm= commandline boot interface must be constrained (there are serious risks in allowing activation of certain DM targets without first using userspace tools to check the validity of associated metadata, as is done by the DM thin and cache targets). Also, all targets supported must be upstream. "linear", "verity" and "bootcache" DM targets are referenced in Documentation, "bootcache" must be a Google target. I'm not aware of it. Mike -- dm-devel mailing list dm-devel@redhat.com https://www.redhat.com/mailman/listinfo/dm-devel
Re: [dm-devel] [PATCH 0/2] boot to a mapped device
On Thu, Sep 27, 2018 at 7:23 AM, Mike Snitzer wrote: > On Wed, Sep 26 2018 at 3:16am -0400, > Richard Weinberger wrote: > >> Helen, >> >> On Wed, Sep 26, 2018 at 7:01 AM Helen Koike >> wrote: >> > >> > This series is reviving an old patchwork. >> > Booting from a mapped device requires an initramfs. This series is >> > allows for device-mapper targets to be configured at boot time for >> > use early in the boot process (as the root device or otherwise). >> >> What is the reason for this patch series? >> Setting up non-trivial root filesystems/storage always requires an >> initramfs, there is nothing >> wrong about this. > > Exactly. If phones or whatever would benefit from this patchset then > say as much. I think some of the context for the series was lost in commit logs, but yes, both Android and Chrome OS do not use initramfs. The only thing that was needed to do this was being able to configure dm devices on the kernel command line, so the overhead of a full initramfs was seen as a boot time liability, a boot image size liability (e.g. Chrome OS has a limited amount of storage available for the boot image that is covered by the static root of trust signature), and a complexity risk: everything that is needed for boot could be specified on the kernel command line, so better to avoid the whole initramfs dance. So, instead, this plumbs the dm commands directly instead of bringing up a full userspace and performing ioctls. > I will not accept this patchset at this time. > >> > Example, the following could be added in the boot parameters. >> > dm="lroot,,,rw, 0 4096 linear 98:16 0, 4096 4096 linear 98:32 0" >> > root=/dev/dm-0 >> >> Hmmm, the new dm= parameter is anything but easy to get right. > > No, it isn't.. exposes way too much potential for users hanging > themselves. IIRC, the changes in syntax were suggested back when I was trying to drive this series: https://www.redhat.com/archives/dm-devel/2016-February/msg00199.html And it matches the "concise" format in dmsetup: https://sourceware.org/git/?p=lvm2.git;a=commit;h=827be01758ec5adb7b9d5ea75b658092adc65534 What do you feel are next steps? Thanks! -Kees -- Kees Cook Pixel Security -- dm-devel mailing list dm-devel@redhat.com https://www.redhat.com/mailman/listinfo/dm-devel
Re: [dm-devel] dm thin: data block's ref count is not zero but not belong to any device.
On Tue, Sep 25, 2018 at 11:13:17PM -0400, monty wrote: > > Hi! I met a problem of dm-thin: a thin-pool has no volumes but its > nr_free_blocks_data is not zero. I guess the scene of this problem like: > a. create a thin volume thin01, size is 10GB; > b. write 10GB to thin01; > c. create a snapshot thin01-snap, orig is thin01; > d. write 10GB to thin01-snap; > e. for a data block of thin01-snap, which will be written by user, will > experience following steps: > 1. alloc a data block m firstly; > 2. wirte data to data block m; > 3. bio callback and assign data block m to thin01-snap. > If power loss happens between step 2 and step 3, data block will not > belong to any device but its ref count is not zero. > Is it a problem? How to solve this problem? Yes, there are a couple of ways this can happen, a dump and restore of the metadata will repair it. - Joe > > -- > dm-devel mailing list > dm-devel@redhat.com > https://www.redhat.com/mailman/listinfo/dm-devel -- dm-devel mailing list dm-devel@redhat.com https://www.redhat.com/mailman/listinfo/dm-devel
Re: [dm-devel] [PATCH 0/2] boot to a mapped device
On Wed, Sep 26 2018 at 3:16am -0400, Richard Weinberger wrote: > Helen, > > On Wed, Sep 26, 2018 at 7:01 AM Helen Koike wrote: > > > > This series is reviving an old patchwork. > > Booting from a mapped device requires an initramfs. This series is > > allows for device-mapper targets to be configured at boot time for > > use early in the boot process (as the root device or otherwise). > > What is the reason for this patch series? > Setting up non-trivial root filesystems/storage always requires an > initramfs, there is nothing > wrong about this. Exactly. If phones or whatever would benefit from this patchset then say as much. I will not accept this patchset at this time. > > Example, the following could be added in the boot parameters. > > dm="lroot,,,rw, 0 4096 linear 98:16 0, 4096 4096 linear 98:32 0" > > root=/dev/dm-0 > > Hmmm, the new dm= parameter is anything but easy to get right. No, it isn't.. exposes way too much potential for users hanging themselves. -- dm-devel mailing list dm-devel@redhat.com https://www.redhat.com/mailman/listinfo/dm-devel
