On Wed, 08 Mar 2023 09:33:52 +1100 "NeilBrown" <neilb@xxxxxxx> wrote: > On Tue, 07 Mar 2023, Mariusz Tkaczyk wrote: > > On Mon, 06 Mar 2023 08:21:07 +1100 > > "NeilBrown" <neilb@xxxxxxx> wrote: > > > > > On Sat, 04 Mar 2023, Song Liu wrote: > > > > + Jes. > > > > > > > > It appeared to me that we can assemble the array if we have any of the > > > > following: > > > > 1. Enable CONFIG_BLOCK_LEGACY_AUTOLOAD; > > > > 2. Have a valid /etc/mdadm.conf; > > > > 3. Update mdadm to handle this case. (I tried some ugly hacks, which > > > > worked but weren't clean). > > > > > > > > Since we eventually would like to get rid of > > > > CONFIG_BLOCK_LEGACY_AUTOLOAD, I think we need mdadm to handle this > > > > properly. But the logistics might be complicated, as > > > > mdadm are shipped separately. > > > > > > > > Jes, what do you think about this? AFAICT, we need to update the logic > > > > in mdopen.c:create_mddev(). > > > > > > mdadm already handles this, but only if > > > CREATE names=yes > > > is present in /etc/mdadm.conf > > > > Hi, > > > > "CREATE names=yes" enforces creation of /dev/md_name arrays instead of > > /dev/mdXXX. It is a large change for users, too aggressive IMO. It will > > destroy many setups. > > > > To resolve it, we need is to use create_named_array() but respect old naming > > convention. We already have find_free_devnm(), and we are able to keep > > consistency because we can create 'mdXXX': > > > > /sys/module/md_mod/parameters # echo md125 > new_array > > > > /sys/module/md_mod/parameters # ll /sys/block/md125 > > lrwxrwxrwx 1 root root 0 Mar 7 10:54 /sys/block/md125 -> > > ../devices/virtual/block/md125 > > > > That will require adjustments in mdadm, but I think that we can keep > > names the same way. I created the test for verification of base creation > > flows, we can use it to avoid regression: > > https://git.kernel.org/pub/scm/utils/mdadm/mdadm.git/tree/tests/00createnames > > > > Thoughts? > > Yes, that is probably sensible. > > It would be nice to have a way to expose the "names=yes" functionality > more obviously. I think people would generally prefer it (/proc/mdstat > becomes more meaningful) but I agree that forcing it on people is the > the best approach. > > Maybe a super-block flag that enables it for that array, and we start > setting that flag when creating new arrays? > That is controversial. I don't feel that using metadata to resolve Linux issue is as a good way. It will work for native for sure but for IMSM it is not such simple. I think that we can handle it by config file. When we set "ARRAY /dev/mdXXX" then it is honored. I'm familiar with such cases, that works. In such case link may or may not be generated so far I remember but... nobody cares if array name is meaningful and we can fix that too. It seems to not be a big deal. I would like to propose doing same for 'names'. If there is no config or name is set to "/dev/md/name" it should work as now. So, if someone would need backward compatibility we can add flag to --detail and --examine breifs forces that, let say --use-link-as-name. By default "ARRAY /dev/md_name" entry will be generated. My PoV is based on IMSM, there may be small differences between IMSM and native but I think that it applies everywhere. Thanks, Mariusz
