Re: Wrong Data Pointer-XFS File system

David Chinner
2007-06-25T23:28:32Z

On Thu, Jun 21, 2007 at 11:23:35PM -0700, Sandy1 wrote:
>
> Hi,
> I am Using SuSe 10.0 with Xfs file system. I am working on a File system
> based project. During the initial research in On disk layout of File system
> , i found data pointer problem. I was not able to get the data location as
> per pointed by "absolute block no." in "xfs_bmbt_rec" extent pointers.

The xfs_bmbt_rec holds the address in FSB format, not DADDR format.

> When i create any file in 0th (zero`th) AG in that case i am able to reach
> on proper location by using "absolute block no." pointer.
>
> But when i create any file in 1st or in 2nd AG and so on. I never got the
> file data at the location pointed by "absolute block no.". I always found
> the file data before the the pointed address.

FSB notation is sparse representation.

> I am not getting any value in Superblock that tells me about difference in
> pointer location with actual data.
>
> This value always becomes multiple of the AG number.
>
> Please help to get out from this problem.
>
> Is there any other calculation for finding the data locations.

man xfs_db. Search for "convert".

Cheers,

Dave.
--
Dave Chinner
Principal Engineer
SGI Australian Software Group