blktrace and xfs_db block offset mismatch

[Sushma R]

Hi,

I ran blktrace while reading a file on XFS partition and here's it's output.

8,17   3        1    22.065944956  5489  D   R 20973896 + 8 [cat]

Using xfs_db, I dumped the inode for the same file and it shows the
following as its data extents.

u.bmx[0] = [startoff,startblock,blockcount,extentflag] 0:[0,2621481,1,0]

I understand that blktrace reports in 512-byte sectors while xfs_db in
filesystem block size (which is the default 4KB on my setup).
Converting blktrace offset to fs block = 2621737 which is close to the data
extent startblock (2621481), but still off by 256 fs blocks.

Could someone please help understand the reason for this mismatch?

Thanks,
Sushma
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://oss.sgi.com/pipermail/xfs/attachments/20140927/c77149b9/attachment.html>