On 07/31/2014 08:19 PM, Matthew Wilcox wrote: > On Thu, Jul 31, 2014 at 06:28:37PM +0300, Boaz Harrosh wrote: >> Matthew what is your opinion about this, do we need to push for removal >> of the partition dead code which never worked for brd, or we need to push >> for fixing and implementing new partition support for brd? > > Fixing the code gets my vote. brd is useful for testing things ... and > sometimes we need to test things that involve partitions. > OK I'm on it, its what I'm doing today. rrr I manged to completely trash my vm by doing 'make install' of util-linux and after reboot it never recovered, I remember that mount complained about a now missing library and I forgot and rebooted, that was the end of that. Anyway I installed a new fc20 system wanted that for a long time over my old fc18 >> Also another thing I saw is that if we leave the flag >> GENHD_FL_SUPPRESS_PARTITION_INFO >> >> then mount -U UUID stops to work, regardless of partitions or not, >> this is because Kernel will not put us on /proc/patitions. >> I'll submit another patch to remove it. > > Yes, we should probably fix that too. > Yes this is good stuff. I found out about the gpt option in fdisk that's really good stuff because it gives you a PARTUUID even before the mkfs, and the partitions are so mach more logical. But only without that flag >> BTW I hit another funny bug where the partition beginning was not >> 4K aligned apparently fdisk lets you do this if the total size is small >> enough (like 4096 which is default for brd) so I ended up with accessing >> sec zero, the supper-block, failing because of the alignment check at >> direct_access(). > > That's why I added on the partition start before doing the alignment > check :-) > Yes, exactly, I had very similar code to yours. I moved to your code now First patch in the set is your patch 4/22 squashed with the modifications you sent, then my fix, then the getgeo patch, then the remove of the flag. But I'm still fighting fdisk's sector math, I can't for the life of me figure out fdisk math, and it is all too easy to create a partition schema that has an unaligned first/last sector. I can observe and see the dis-alignment when the partitions are first created, I can detect that at prd_probe time. I can probably fix it by this logic: When first detecting a new partition ie if bd_part->start_sect is not aligned round-up to PAGE_SIZE. Then subtract from bd_part->nr_sects the fixed up size and round-down bd_part->nr_sects to PAGE_SIZE This way I still live inside the confined space that fdisk gave me but only IO within largest aligned space. The leftover sectors are just wasted space. >> Do you know of any API that brd/prd can do to not let fdisk do this? >> I'm looking at it right now I just thought it is worth asking. > > I think it's enough to refuse the mount. That feels like a patch to > ext2/4 (or maybe ext2/4 has a way to start the filesystem on a different > block boundary?) > We should not leave this to the FSs to do again and again all over. I wonder if there is some getgeo or some disk properties info somewhere that I can set to force the core block layer to do this for me, I'm surprised that this is the first place we have this problem? Thanks Boaz -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>