Neil Brown wrote: > On Tuesday April 24, david@xxxxxxxxxxxx wrote: >> Neil, isn't it easy to just do this after an assemble? > > Yes, but it should not be needed, and I'd like to understand why it > is. > One of the last things do_md_run does is > mddev->changed = 1; > > When you next open /dev/md_d0, md_open is called which calls > check_disk_change(). > This will call into md_fops->md_media_changed which will return the > value of mddev->changed, which will be '1'. > So check_disk_change will then call md_fops->revalidate_disk which > will set mddev->changed to 0, and will then set bd_invalidated to 1 > (as bd_disk->minors > 1 (being 64)). > > md_open will then return into do_open (in fs/block_dev.c) and because > bd_invalidated is true, it will call rescan_partitions and the > partitions will appear. > > Hmmm... there is room for a race there. If some other process opens > /dev/md_d0 before mdadm gets to close it, it will call > rescan_partitions before first calling bd_set_size to update the size > of the bdev. So when we try to read the partition table, it will > appear to be reading past the EOF, and will not actually read > anything.. > > I guess udev must be opening the block device at exactly the wrong > time. > > I can simulate this by holding /dev/md_d0 open while assembling the > array. If I do that, the partitions don't get created. > Yuck. > > Maybe I could call bd_set_size in md_open before calling > check_disk_change.. > > Yep, this patch seems to fix it. Could you confirm? almost... teak:~# mdadm --assemble /dev/md_d0 --auto=parts /dev/sd[bcdef]1 mdadm: /dev/md_d0 has been started with 5 drives. teak:~# mount /media teak:~# umount /media teak:~# mdadm --stop /dev/md_d0 mdadm: stopped /dev/md_d0 teak:~# mdadm --assemble /dev/md_d0 --auto=parts /dev/sd[bcdef]1 mdadm: /dev/md_d0 has been started with 5 drives. teak:~# mount /media mount: No such file or directory teak:~# mount /media teak:~# (second mount succeeds second time around) md: md_d0 stopped. md: bind<sdc1> md: bind<sdd1> md: bind<sdb1> md: bind<sdf1> md: bind<sde1> raid5: device sde1 operational as raid disk 0 raid5: device sdf1 operational as raid disk 4 raid5: device sdb1 operational as raid disk 3 raid5: device sdd1 operational as raid disk 2 raid5: device sdc1 operational as raid disk 1 raid5: allocated 5236kB for md_d0 raid5: raid level 5 set md_d0 active with 5 out of 5 devices, algorithm 2 RAID5 conf printout: --- rd:5 wd:5 disk 0, o:1, dev:sde1 disk 1, o:1, dev:sdc1 disk 2, o:1, dev:sdd1 disk 3, o:1, dev:sdb1 disk 4, o:1, dev:sdf1 md_d0: bitmap initialized from disk: read 1/1 pages, set 0 bits, status: 0 created bitmap (10 pages) for device md_d0 md_d0: p1 p2 Filesystem "md_d0p1": Disabling barriers, not supported with external log device XFS mounting filesystem md_d0p1 Ending clean XFS mount for filesystem: md_d0p1 md: md_d0 stopped. md: unbind<sde1> md: export_rdev(sde1) md: unbind<sdf1> md: export_rdev(sdf1) md: unbind<sdb1> md: export_rdev(sdb1) md: unbind<sdd1> md: export_rdev(sdd1) md: unbind<sdc1> md: export_rdev(sdc1) md: md_d0 stopped. md: bind<sdc1> md: bind<sdd1> md: bind<sdb1> md: bind<sdf1> md: bind<sde1> raid5: device sde1 operational as raid disk 0 raid5: device sdf1 operational as raid disk 4 raid5: device sdb1 operational as raid disk 3 raid5: device sdd1 operational as raid disk 2 raid5: device sdc1 operational as raid disk 1 raid5: allocated 5236kB for md_d0 raid5: raid level 5 set md_d0 active with 5 out of 5 devices, algorithm 2 RAID5 conf printout: --- rd:5 wd:5 disk 0, o:1, dev:sde1 disk 1, o:1, dev:sdc1 disk 2, o:1, dev:sdd1 disk 3, o:1, dev:sdb1 disk 4, o:1, dev:sdf1 md_d0: bitmap initialized from disk: read 1/1 pages, set 0 bits, status: 0 created bitmap (10 pages) for device md_d0 md_d0: p1 p2 XFS: Invalid device [/dev/md_d0p2], error=-2 Filesystem "md_d0p1": Disabling barriers, not supported with external log device XFS mounting filesystem md_d0p1 Ending clean XFS mount for filesystem: md_d0p1 - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
