Re: Errors in btrfsck after converting ext2 FS to btrfs.

["Yan, Zheng " <yanzheng@21cn.com>]

On Sun, Oct 18, 2009 at 10:35 PM, Prasad Joshi <prasadjoshi124@gmail.co=
m> wrote:
> Hi,
>
> I tried using the btrfs-convert utility to convert the ext2 fs to
> btrfs. After the conversion was over, just to verify the correctness
> of operation, ran btrfsck on the device. It showed errors 800. I am
> not sure what does it mean, so thought of repoting it on mailing list=
=2E
>
> # btrfsck /dev/sdb
> root 256 inode 257 errors 800
> found 1105965056 bytes used err is 1
> total csum bytes: 192576
> total tree bytes: 459956224
> total fs tree bytes: 449585152
> btree space waste bytes: 191448023
> file data blocks allocated: 843206656
> referenced 843206656
> Btrfs v0.19-3-g6f3cf25-dirty

"root 256 inode 257" is the ext2 image file. Checksum for file extents =
in
the ext2 image file is very special, so btrfsck treat it as error. This=
 error
has no harm,  it will go away after deleting the ext2 image file.

>
> I also found that, after the conversion of FS from ext2 to btrfs
> %usage gone up drastically. I mean before the conversion ext2 FS was
> 22% full but then converted btrfs is 64% used.
>
> Steps Followed
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> 1. Created an ext2 filesystem of size 2G
> 2. Created about 178 files of size 1M in a directory. FS was 11% full
> after the operation.
> 3. In another directory create near about 1 Lac files of very small
> size (2K). I kept on creating files till the number of available
> inodes were exhausted.
>
> # fsck /dev/sdb
> fsck 1.41.3 (12-Oct-2008)
> e2fsck 1.41.3 (12-Oct-2008)
> /dev/sdb: clean, 131072/131072 files, 188721/524288 blocks
>
> At this point df -kh output showed that FS as 22% full
>
> 4. Tried to convert the ext2 FS to btrfs using btrfs-convert utility
>
> # btrfs-convert /dev/sdb
> creating btrfs metadata.
> creating ext2fs image file.
> cleaning up system chunk.
> conversion complete.
>
> 5. Ran btrfsck.
>
> 6. Mounted the file system
>
> # df -kh
> Filesystem=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 Size=A0 Used Avail Use% M=
ounted on
> ....
> ....
> tmpfs=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 251M=A0 104K=A0=
 251M=A0=A0 1% /dev/shm
> /dev/sdb=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 2.0G=A0 1.3G=A0 740M=A0=
 64% /mnt/fs
>
> As you can see df displays FS is 64% full, when infact before
> conversion it was onlly 22% full. Why is so much increase in
> percentage usage?

This is a accounting bug, it's already fixed in btrfs-progs-unstable tr=
ee.

Yan, Zheng
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