On Thu, Jul 02, 2020 at 09:11:20AM +0000, Rebraca Dejan (BSOT/PJ-ES1-Bg) wrote: > Hi all, > > I'm collecting file extents for our application from BtrFs filesystem image. > I've noticed that for some files a get the "wrong" physical offset for > start of the extent. I verified it using hexdump of the filesystem > image: when dump the content starting from the address returned from > FIEMAP ioctl, I see that the content is absolutely different from the > content of the file itself. Also, the FIEMAP ioctl reports regular > extent, it is not inline. There are 3 address spaces: - device physical offsets - filesystem physical offsets - filesystem logical offsets What you seem to expect is that device physical and filesystem physical and the same. This is not true in general in btrfs and fiemap will return only the filesystem offsets. To get to the device offsets you'd need to do the reverse mapping.
