On Fri, Jul 21, 2023 at 02:38:45PM +0800, Mark-PK Tsai wrote: > > On Mon, Jul 17, 2023 at 09:57:28AM +0800, Mark-PK Tsai wrote: > > > > On Sun, Jul 16, 2023, 11:16 AM Greg KH <gre...@linuxfoundation.org> > > > > wrote: > > > > > > > > > On Thu, Jul 13, 2023 at 01:58:37PM +0800, Mark-PK Tsai wrote: > > > > > > From: Peter Korsgaard <pe...@korsgaard.com> > > > > > > > > > > > > Just calling wait_for_device_probe() is not enough to ensure that > > > > > > asynchronously probed block devices are available (E.G. mmc, usb), > > > > > > so > > > > > > add a "dm-mod.waitfor=<device1>[,..,<deviceN>]" parameter to get > > > > > > dm-init to explicitly wait for specific block devices before > > > > > > initializing the tables with logic similar to the rootwait logic > > > > > > that > > > > > > was introduced with commit cc1ed7542c8c ("init: wait for > > > > > > asynchronously scanned block devices"). > > > > > > > > > > > > E.G. with dm-verity on mmc using: > > > > > > dm-mod.waitfor="PARTLABEL=hash-a,PARTLABEL=root-a" > > > > > > > > > > > > [ 0.671671] device-mapper: init: waiting for all devices to be > > > > > available before creating mapped devices > > > > > > [ 0.671679] device-mapper: init: waiting for device > > > > > > PARTLABEL=hash-a > > > > > ... > > > > > > [ 0.710695] mmc0: new HS200 MMC card at address 0001 > > > > > > [ 0.711158] mmcblk0: mmc0:0001 004GA0 3.69 GiB > > > > > > [ 0.715954] mmcblk0boot0: mmc0:0001 004GA0 partition 1 2.00 MiB > > > > > > [ 0.722085] mmcblk0boot1: mmc0:0001 004GA0 partition 2 2.00 MiB > > > > > > [ 0.728093] mmcblk0rpmb: mmc0:0001 004GA0 partition 3 512 KiB, > > > > > chardev (249:0) > > > > > > [ 0.738274] mmcblk0: p1 p2 p3 p4 p5 p6 p7 > > > > > > [ 0.751282] device-mapper: init: waiting for device > > > > > > PARTLABEL=root-a > > > > > ... > > > > > > [ 0.751306] device-mapper: init: all devices available > > > > > > [ 0.751683] device-mapper: verity: sha256 using implementation > > > > > "sha256-generic" > > > > > > [ 0.759344] device-mapper: ioctl: dm-0 (vroot) is ready > > > > > > [ 0.766540] VFS: Mounted root (squashfs filesystem) readonly on > > > > > device 254:0. > > > > > > > > > > > > Signed-off-by: Peter Korsgaard <pe...@korsgaard.com> > > > > > > Signed-off-by: Mike Snitzer <snit...@kernel.org> > > > > > > Cc: sta...@vger.kernel.org > > > > > > Signed-off-by: Mark-PK Tsai <mark-pk.t...@mediatek.com> > > > > > > --- > > > > > > .../admin-guide/device-mapper/dm-init.rst | 8 +++++++ > > > > > > drivers/md/dm-init.c | 22 > > > > > > ++++++++++++++++++- > > > > > > 2 files changed, 29 insertions(+), 1 deletion(-) > > > > > > > > > > What is the git commit id of this change in Linus's tree? > > > > > > > > > > thanks, > > > > > > > > > > greg k-h > > > > > > > > > > > > > > > > > > Hey Greg, > > > > > > > > This change shouldn't be backported to stable@. It is a feature, if > > > > Mark-PK feels they need it older kernels they need to carry the change > > > > in their own tree. Or at a minimum they need to explain why this > > > > change is warranted in stable@. > > > > > > Thanks for your comment. > > > The reason why we think this should be backported to stable kernel is > > > that it actually fix the potential race condition when make block > > > device probe async in stable kernel. > > > And we'd like to fix this upstream rather than just take it in > > > our custom tree. > > > > Potential race condition, is this actually able to be hit in real life? > > Yes it hanppened, and it can lead the kernel init process stuck in > the root wait loop. > > Below is the log. > (I add 20 seconds delay in mtk_mci probe to quick reproduce it.) > > * Before apply this pactch > [ 0.368594][ T1] device-mapper: init: waiting for all devices to be > available before creating mapped devices > [ 21.673047][ T45] probe of 1c660000.mtk-mmc-fcie returned 0 after > 21541020 usecs > [ 21.673061][ T45] mtk_mci 1c660000.mtk-mmc-fcie: driver mtk_mci async > attach completed: 0 > [ 21.680006][ T1] device-mapper: table: 254:0: verity: Data device > lookup failed <--------------- start after mtk_mci probe done > [ 21.680012][ T1] device-mapper: ioctl: error adding target to table > <--------------------------- won't create /dev/dm-0 > [ 21.680067][ T67] mmc0: new HS400 Enhanced strobe MMC card at address > 0001 > [ 21.680184][ T67] bus: 'mmc': __driver_probe_device: matched device > mmc0:0001 with driver mmcblk > [ 21.680192][ T67] bus: 'mmc': really_probe: probing driver mmcblk with > device mmc0:0001 > [ 21.680500][ T67] mmcblk0: mmc0:0001 016G01 14.5 GiB > [ 21.683404][ T67] mmcblk0: p1 p2 p3 p4 p5 p6 p7 p8 p9 p10 p11 p12 p13 > p14 p15 p16 p17 p18 p19 p20 p21 p22 p23 p24 p25 p26 p27 p28 p29 > [ 21.686152][ T67] mmcblk0boot0: mmc0:0001 016G01 8.00 MiB > [ 21.687166][ T67] mmcblk0boot1: mmc0:0001 016G01 8.00 MiB > [ 21.687955][ T67] mmcblk0rpmb: mmc0:0001 016G01 4.00 MiB, chardev (238:0) > [ 21.687977][ T67] driver: 'mmcblk': driver_bound: bound to device > 'mmc0:0001' > [ 21.688004][ T67] bus: 'mmc': really_probe: bound device mmc0:0001 to > driver mmcblk > [ 21.688010][ T67] probe of mmc0:0001 returned 0 after 7819 usecs > [ 21.688166][ T1] Waiting for root device /dev/dm-0... > [ 41.023192][ T1] driver_probe_done: probe_count = 0 > ... can't exit from the root wait loop > > * After apply this patch and add dm-mod.waitfor="PARTLABEL=rootfs" > [ 0.368417][ T1] device-mapper: init: waiting for all devices to be > available before creating mapped devices > [ 21.672749][ T45] probe of 1c660000.mtk-mmc-fcie returned 0 after > 21540992 usecs > [ 21.672767][ T45] mtk_mci 1c660000.mtk-mmc-fcie: driver mtk_mci async > attach completed: 0 > [ 21.672774][ T1] device-mapper: init: waiting for device > PARTLABEL=rootfs ... > [ 21.672869][ T43] mtk_mci 1c660000.mtk-mmc-fcie: eMMC: HS400 5.1 200MHz > [ 21.679743][ T43] mmc0: new HS400 Enhanced strobe MMC card at address > 0001 > [ 21.679852][ T43] bus: 'mmc': __driver_probe_device: matched device > mmc0:0001 with driver mmcblk > [ 21.679858][ T43] bus: 'mmc': really_probe: probing driver mmcblk with > device mmc0:0001 > [ 21.680204][ T43] mmcblk0: mmc0:0001 016G01 14.5 GiB > [ 21.682866][ T43] mmcblk0: p1 p2 p3 p4 p5 p6 p7 p8 p9 p10 p11 p12 p13 > p14 p15 p16 p17 p18 p19 p20 p21 p22 p23 p24 p25 p26 p27 p28 p29 > [ 21.685579][ T43] mmcblk0boot0: mmc0:0001 016G01 8.00 MiB > [ 21.686631][ T43] mmcblk0boot1: mmc0:0001 016G01 8.00 MiB > [ 21.687533][ T43] mmcblk0rpmb: mmc0:0001 016G01 4.00 MiB, chardev (238:0) > [ 21.687559][ T43] driver: 'mmcblk': driver_bound: bound to device > 'mmc0:0001' > [ 21.687585][ T43] bus: 'mmc': really_probe: bound device mmc0:0001 to > driver mmcblk > [ 21.687591][ T43] probe of mmc0:0001 returned 0 after 7732 usecs > [ 21.687838][ T1] device-mapper: init: all devices available > <---------------------------------- start after PARTLABEL=rootfs is ready > [ 21.688155][ T1] device-mapper: verity: sha1 using implementation > "sha1-generic" > [ 21.688975][ T1] device-mapper: ioctl: dm-0 (dm-verity) is ready >
Ok, seems sane, I'll queue this up for 6.1.y and 5.15.y now. thanks, greg k-h -- dm-devel mailing list dm-devel@redhat.com https://listman.redhat.com/mailman/listinfo/dm-devel