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? NeilBrown > > BTW. I wanted to get rid of this legacy "create_on_open" from mdadm anyway but > never had time to. If you agree, I can proceed with fixing it. > > Thanks, > Mariusz >
