Re: Building a brtfs filesystem < 70M?

[Saul Wold <sgw@linux.intel.com>]

On 03/11/2014 06:10 PM, quwenruo@cn.fujitsu.com wrote:
> On Tue, 11 Mar 2014 09:37:00 -0700, Zach Brown wrote:
>>> There seems to be an issue if we try to build a btrfs based FS that
>>> is less than 70M, we get the following assertion failure:
>>>
>>> mkfs.btrfs: extent-tree.c:2682: btrfs_reserve_extent: Assertion
>>> `!(ret)' failed.
>>> mkfs.btrfs -b 104857600 -r rootfs rootfs.btrfs
>> Honestly, the path of least resistance is probably to avoid the -r
>> option all together.  As you've found, it's not reliable.
>>
>> I'd take the time to roll the infrastrcture to populate the image by
>> writing to a mounted image with the kernel code.
>>
>> - z
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> I although agree with the mount + cp(kernel) way to populate the filesystem.
> Also I think the implement of "-r" should be somewhat like mount+cp
> other than the current way,
> since the userland implement is noticeably slow than kernel way.
>
> Cc:Donggeun Kim
> I also wonder why "-r" option is needed, since IMO the "-r" options is
> only needed
> if the filesystem is full readonly and must be populated on
> initialization like squashfs.
> And since btrfs is a filesystem that can be read and write,
> the "-r" option is not somewhat needed.
>
> So I prefer to remove the "-r" option.
>
Please dont remove the -r option, as you point out above it's used from 
userland.  The Yocto Project / OE-Core uses this option to build a put a 
rootfs into a filesystem image in userland without requiring root 
permissions, we use something call pseudo (it a smarter version of 
fakeroot) to lay down a root filesytem.

The patch from Gui worked well for our purposes, we are no longer 
failing to build the filesystem image.

Thanks

Sau!

>
> Thanks
> Qu
>