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Thu, 26 Sep 2024 15:55:50 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id SlyoCwaE9WaXEwAAD6G6ig (envelope-from ); Thu, 26 Sep 2024 15:55:50 +0000 Content-Type: text/plain; charset=utf-8 Precedence: bulk X-Mailing-List: linux-bcache@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3776.700.51\)) Subject: Re: multipath'd bcache device From: Coly Li In-Reply-To: Date: Thu, 26 Sep 2024 23:55:26 +0800 Cc: Bcache Linux Content-Transfer-Encoding: quoted-printable Message-Id: <01034362-64FB-4D49-ACC0-496076543F2F@suse.de> References: <08E9CAFD-1ECC-4B46-8F0D-7124716E76EF@suse.de> <63707B6C-C735-4706-98E4-40C061F3FDB6@suse.de> To: Mitchell Dzurick X-Mailer: Apple Mail (2.3776.700.51) X-Spam-Score: -4.30 X-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; APPLE_MAILER_COMMON(0.00)[]; FUZZY_BLOCKED(0.00)[rspamd.com]; RCVD_VIA_SMTP_AUTH(0.00)[]; ARC_NA(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; RCVD_TLS_ALL(0.00)[]; RCPT_COUNT_TWO(0.00)[2]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; MIME_TRACE(0.00)[0:+]; RCVD_COUNT_TWO(0.00)[2]; TO_DN_ALL(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:mid,suse.de:email,imap1.dmz-prg2.suse.org:helo] X-Spam-Flag: NO X-Spam-Level: I doubt bcache_allocator involved in this issue. After the cache device = registered, an extra refcount will be added to the block device, this is = expected. And Bcache is fine with multipath, because another path has identical = UUID, the registration just fails and exits. Why multipath was not initialized at the first place, this is an open = question for me. Coly Li > 2024=E5=B9=B49=E6=9C=8826=E6=97=A5 09:15=EF=BC=8CMitchell Dzurick = =E5=86=99=E9=81=93=EF=BC=9A >=20 > Is it perhaps the bcache_allocator interacting with the block device? > I dug around a little bit but couldn't conclude if the allocator was > interacting with the block device, but there might be a better way to > confirm that, which I am not aware of. >=20 > On Wed, Sep 25, 2024 at 5:55=E2=80=AFPM Mitchell Dzurick > wrote: >>=20 >> Yes, sdc is another path to sdd. The lsblk command looks like this: >>=20 >> NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINTS >> fd0 2:0 1 4K 0 disk >> sda 8:0 0 20G 0 disk >> =E2=94=94=E2=94=80mpatha 252:1 0 20G 0 mpath >> =E2=94=9C=E2=94=80mpatha-part1 252:2 0 1M 0 part >> =E2=94=94=E2=94=80mpatha-part2 252:3 0 20G 0 part / >> sdb 8:16 0 20G 0 disk >> =E2=94=94=E2=94=80mpatha 252:1 0 20G 0 mpath >> =E2=94=9C=E2=94=80mpatha-part1 252:2 0 1M 0 part >> =E2=94=94=E2=94=80mpatha-part2 252:3 0 20G 0 part / >> sdc 8:32 0 1G 0 disk >> =E2=94=94=E2=94=80mpathb 252:0 0 1G 0 mpath >> sdd 8:48 0 1G 0 disk >> =E2=94=94=E2=94=80mpathb 252:0 0 1G 0 mpath >> sr0 11:0 1 2.6G 0 rom >>=20 >> Where I invoke the KVM command like this: >> $ kvm -m 2048 -boot c \ >> -cdrom ./oracular-live-server-amd64.iso \ >> -device virtio-scsi-pci,id=3Dscsi \ >> -drive file=3Dimage.img,if=3Dnone,id=3Dsda,format=3Draw,file.locking= =3Doff \ >> -device scsi-hd,drive=3Dsda,serial=3D0001 \ >> -drive if=3Dnone,id=3Dsdb,file=3Dimage.img,format=3Draw,file.locking= =3Doff \ >> -device scsi-hd,drive=3Dsdb,serial=3D0001 \ >> -drive file=3Dimage2.img,if=3Dnone,id=3Dsdc,format=3Draw,file.lockin= g=3Doff \ >> -device scsi-hd,drive=3Dsdc,serial=3D0002 \ >> -drive if=3Dnone,id=3Dsdd,file=3Dimage2.img,format=3Draw,file.lockin= g=3Doff \ >> -device scsi-hd,drive=3Dsdd,serial=3D0002 \ >> -netdev user,id=3Dnet0,hostfwd=3Dtcp::2222-:22 \ >> -device virtio-net-pci,netdev=3Dnet0 >>=20 >>> Do you know why multipath failed to get device 252:1 ? And why I = don=E2=80=99t see backing device of bcache here ? >> I'm not sure at the moment, that's what I'm trying to get to the = bottom of. >>=20 >> The one thing that lead me down this path of bcache being involved >> with this issue, is simply that by `sudo apt purge bcache-tools` I = see >> the device is picked up by multipath-tools successfully, so it seems >> something in the bcache-tools package is causing this. >>=20 >> Is there any specific thing you'd like me to look for, or a command >> you'd like me to run? >>=20 >> I originally assumed that the reason multipath failed was that the >> bcache udev rule opens the device file, but that is clearly a >> misunderstanding since the multipath udev rules run first, so >> _something_ is intereacting with the device early and making it busy, >> I'm just not sure what right now. >>=20 >> On Sun, Sep 22, 2024 at 6:55=E2=80=AFPM Coly Li = wrote: >>>=20 >>> Hi Mitchell, >>>=20 >>> Yes I can see the log. >>>=20 >>> [ 1.226296] device-mapper: multipath service-time: version 0.3.0 = loaded >>> [ 1.277039] device-mapper: table: 252:1: multipath: error getting = device (-EBUSY) >>> [ 1.277086] device-mapper: ioctl: error adding target to table >>> [ 1.300407] bcache: bch_journal_replay() journal replay done, 0 keys = in 1 entries, seq 1 >>> [ 1.301650] bcache: register_cache() registered cache device sdd >>> [ 1.301748] bcache: register_cache_worker() error /dev/sdc: fail to = register cache device >>>=20 >>>=20 >>> =46rom the above lines, it seems device mapper starts early, but = both dm and bcache encounter a busy device. >>> Then bcache registered sdd successfully, and not register sdc. But I = don=E2=80=99t see other information about how the backing device was = registered. >>>=20 >>> =46rom the following message, >>> [ 4.049395] bcache: register_bcache() error : device already = registered >>> [ 4.268997] bcache: register_cache_worker() error /dev/sdc: fail to = register cache device >>>=20 >>> I assume sdc is the another path of sdd? >>> =46rom the logs, it seems all bcache behaviors are expected, except = for no backing device existed/registered. >>>=20 >>> Also I see multipath rule might execute before bcache one, but = explains =E2=80=9C[ 1.277039] device-mapper: table: 252:1: multipath: = error getting device (-EBUSY)=E2=80=9D. I don=E2=80=99t know how it = happens, but this is a suspicious one. >>>=20 >>> Do you know why multipath failed to get device 252:1 ? And why I = don=E2=80=99t see backing device of bcache here ? >>>=20 >>> Thanks. >>>=20 >>> Coly Li >>>=20 >>>> 2024=E5=B9=B49=E6=9C=8820=E6=97=A5 21:11=EF=BC=8CMitchell Dzurick = =E5=86=99=E9=81=93=EF=BC=9A >>>>=20 >>>> Coly, >>>>=20 >>>> Are you able to view this? >>>>=20 >>>> https://gist.github.com/mitchdz/addb44425709fd6df5a6b1b91611b234 >>>>=20 >>>> -Mitch >>>>=20 >>>> On Fri, Sep 20, 2024 at 5:51=E2=80=AFAM Mitchell Dzurick >>>> wrote: >>>>>=20 >>>>> You are right, it seems to be something else than the udev rules. = Let >>>>> me paste the boot messages real quick. >>>>>=20 >>>>> On Fri, Sep 20, 2024 at 5:42=E2=80=AFAM Coly Li = wrote: >>>>>>=20 >>>>>> On my distribution, I see multipath rules is 56-multipath.rules, = it should be executed early than bcache one. I am not an systemd and = boot expert, but what is the order of your multipath rules? >>>>>>=20 >>>>>> Coly Li >>>>>>=20 >>>>>>> 2024=E5=B9=B49=E6=9C=8820=E6=97=A5 19:24=EF=BC=8CMitchell = Dzurick =E5=86=99=E9=81=93=EF=BC=9A >>>>>>>=20 >>>>>>> Coly, >>>>>>>=20 >>>>>>> Yes, I made that observation in multipath-tools upstream bug[0]. >>>>>>>=20 >>>>>>> Ultimately the issue is that the bcache-tools udev rule runs >>>>>>> bcache-register on the device and therefore it can't be opened = by >>>>>>> multipath tools. >>>>>>>=20 >>>>>>> Therefore, the udev rule should wait to run until after = multipath has >>>>>>> a chance to make the maps. I'm not sure if there's any = complications >>>>>>> with moving the rules later into the boot process though, WDYT? >>>>>>>=20 >>>>>>> -Mitch >>>>>>>=20 >>>>>>> On Mon, Sep 9, 2024 at 8:56=E2=80=AFAM Coly Li = wrote: >>>>>>>>=20 >>>>>>>>=20 >>>>>>>>=20 >>>>>>>>> 2024=E5=B9=B49=E6=9C=886=E6=97=A5 07:37=EF=BC=8CMitchell = Dzurick =E5=86=99=E9=81=93=EF=BC=9A >>>>>>>>>=20 >>>>>>>>> Thanks for the response Coly! >>>>>>>>>=20 >>>>>>>>> Apologies on my delay, I was out for a bit and then was sick = =3D=3D lots >>>>>>>>> of catching up to do. >>>>>>>>>=20 >>>>>>>>> Getting back to this, I do see that we have the bcache KCONFIG = value enabled >>>>>>>>>=20 >>>>>>>>> CONFIG_BCACHE_ASYNC_REGISTRATION=3Dy >>>>>>>>>=20 >>>>>>>>> I don't believe this is a race condition issue. If I try to = reload the >>>>>>>>> devmap table with multipath-tools well after boot, I see the = following >>>>>>>>> in dmesg: >>>>>>>>>=20 >>>>>>>>> $ sudo multipath -r >>>>>>>>> [ 8758.157075] device-mapper: table: 252:3: multipath: error = getting >>>>>>>>> device (-EBUSY) >>>>>>>>> [ 8758.158039] device-mapper: ioctl: error adding target to = table >>>>>>>>> [ 8758.256206] device-mapper: table: 252:3: multipath: error = getting >>>>>>>>> device (-EBUSY) >>>>>>>>> [ 8758.256758] device-mapper: ioctl: error adding target to = table >>>>>>>>=20 >>>>>>>> When you see the above kernel message, can you check whether = bcache device is initialized already? >>>>>>>> Or you may post the boot time kernel message as attachment, or = past it somewhere, then let me have a look. >>>>>>>>=20 >>>>>>>> Thanks. >>>>>>>>=20 >>>>>>>>=20 >>>>>>>> Coly Li >>>>>>>>=20 >>>>>>>>=20 >>>>>>>>=20 >>>>>>>>=20 >>>>>>>>>=20 >>>>>>>>> FYI - Since I'm not sure if this is a bug in bcache-tools or >>>>>>>>> multipath-tools, I also made an upstream bug report for >>>>>>>>> multipath-tools at[0]. >>>>>>>>>=20 >>>>>>>>> If there is anything else you'd like me to try, let me know :) >>>>>>>>>=20 >>>>>>>>> [0] - https://github.com/opensvc/multipath-tools/issues/96 >>>>>>>>>=20 >>>>>>>>> On Mon, Aug 12, 2024 at 12:17=E2=80=AFAM Coly Li = wrote: >>>>>>>>>>=20 >>>>>>>>>> Hi Mitchell, >>>>>>>>>>=20 >>>>>>>>>>=20 >>>>>>>>>> It sounds like a timing issue of the initialization scripts. = I assume the cache and backing devices are relative large, so the = initialization takes time. And because the storage is not local, the = remote link contributes more time to wait for the bcache device being = ready. >>>>>>>>>>=20 >>>>>>>>>> If this is the case, then you have to tune the multipath = initialization to wait for longer, or compose a customized script to = start services depending on bcache devices. >>>>>>>>>>=20 >>>>>>>>>> BTW, I assume the bcache Kconfig =E2=80=9CAsynchronous device = registration=E2=80=9D is checked/enabled. If not, maybe check it on can = be a bit helpful. >>>>>>>>>>=20 >>>>>>>>>> Just FYI. >>>>>>>>>>=20 >>>>>>>>>> Coly Li >>>>>>>>>>=20 >>>>>>>>>>> 2024=E5=B9=B48=E6=9C=8812=E6=97=A5 10:54=EF=BC=8CMitchell = Dzurick =E5=86=99=E9=81=93=EF=BC=9A >>>>>>>>>>>=20 >>>>>>>>>>> Thanks for the reply Coly. >>>>>>>>>>>=20 >>>>>>>>>>> I've been able to reproduce this in Ubuntu Noble and = Oracular (24.04 >>>>>>>>>>> && 24.10). It should be an issue in Jammy but haven't tested = that yet. >>>>>>>>>>> The current kernel used in Oracular is 6.8.0-31.31 and the = current >>>>>>>>>>> kernel used in Noble is 6.8.0-40.40. >>>>>>>>>>>=20 >>>>>>>>>>> Unfortunately you need an account to access pastebin. I can = copy that >>>>>>>>>>> information elsewhere for you if that would be helpful, but = I can also >>>>>>>>>>> just gather any extra information you may want from my = testbed. >>>>>>>>>>>=20 >>>>>>>>>>> I also have some steps in the bug report to reproduce this = issue using kvm. >>>>>>>>>>>=20 >>>>>>>>>>> Lastly, if there's any steps you'd like me to try or look = into, I'd be >>>>>>>>>>> glad to hear :) >>>>>>>>>>>=20 >>>>>>>>>>> -Mitch >>>>>>>>>>>=20 >>>>>>>>>>> On Sun, Aug 11, 2024 at 5:31=E2=80=AFAM Coly Li = wrote: >>>>>>>>>>>>=20 >>>>>>>>>>>>=20 >>>>>>>>>>>>=20 >>>>>>>>>>>>> 2024=E5=B9=B48=E6=9C=888=E6=97=A5 09:21=EF=BC=8CMitchell = Dzurick =E5=86=99=E9=81=93=EF=BC=9A >>>>>>>>>>>>>=20 >>>>>>>>>>>>> Hello bcache team. >>>>>>>>>>>>>=20 >>>>>>>>>>>>> I know this project is done and stable as [0] says, but I = have a >>>>>>>>>>>>> question if anyone is around to answer. >>>>>>>>>>>>>=20 >>>>>>>>>>>>> Has bcache devices been tested and supported on = multipath'd disks? I'm >>>>>>>>>>>>> looking into an Ubuntu bug[1], where these 2 projects are = clashing. >>>>>>>>>>>>> I'm wondering if there was any consideration or support = for >>>>>>>>>>>>> multipathing when this project was made. >>>>>>>>>>>>>=20 >>>>>>>>>>>>> Also, your new project, bcachefs, might be hitting the = same scenario. >>>>>>>>>>>>> I haven't had the time to test this though unfortunately. >>>>>>>>>>>>>=20 >>>>>>>>>>>>> Thanks for your time, >>>>>>>>>>>>> -Mitch >>>>>>>>>>>>>=20 >>>>>>>>>>>>> [0] - https://bcache.evilpiepirate.org/#index4h1 >>>>>>>>>>>>> [1] - = https://bugs.launchpad.net/ubuntu/+source/bcache-tools/+bug/1887558 >>>>>>>>>>>>>=20 >>>>>>>>>>>>=20 >>>>>>>>>>>> =46rom the Ubuntu bug report, I don=E2=80=99t see the = kernel version. After parallel and asynchronous initialization was = enabled, the udev rule won=E2=80=99t always occupy the bcache block = device for long time. >>>>>>>>>>>>=20 >>>>>>>>>>>> It might be a bit helpful if you may provide the kernel = version and Ubuntu os version. BTW I don=E2=80=99t have ubuntu account = and cannot access pastern.canonical.com. >>>>>>>>>>>>=20 >>>>>>>>>>>> Thanks. >>>>>>>>>>>>=20 >>>>>>>>>>>> Coly Li >>>>>>>>>>>=20 >>>>>>>>>>=20 >>>>>>>>>=20 >>>>>>>>=20 >>>>>>=20 >>>>=20 >>>=20 >=20