2012/10/1 David Sterba <dave@xxxxxxxx>: > On Fri, Sep 28, 2012 at 11:02:40AM +0800, Robin Dong wrote: >> From: Robin Dong <sanbai@xxxxxxxxxx> >> >> Using mkfs.btrfs like: >> >> mkfs.btrfs -b 1048576 /dev/sda >> >> will report error: >> >> mkfs.btrfs: volumes.c:796: btrfs_alloc_chunk: Assertion `!(ret)' failed. >> Aborted >> >> because the length of dev_extent is 4MB. >> >> But if we use mkfs.btrfs with 8MB total bytes, the newly mounted btrfs filesystem >> would not contain even one empty file. So 12MB will be good min-value for block_count. > > I'm not able to create a single file even on a 12MB filesystem > (with -d single -m single --mixed), so any limit that would let the mkfs > finish normally should be fine. For the single/single case it's 5MB but > for the dup/dup it's 156MB. It's due to the known bug in the blockgroup > creation with multiple devices (applies on dup as well here) that leads > to: > > # btrfs fi df . > System, DUP: total=8.00MB, used=4.00KB > System: total=4.00MB, used=0.00 > Data+Metadata, DUP: total=64.00MB, used=24.00KB > Data+Metadata: total=8.00MB, used=0.00 > > 8*2 + 4 + 64*2 + 8 = 156 > > so, 12M is too small to avoid the mkfs crash. Thanks for your notice! > > david -- -- Best Regard Robin Dong -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
