27.10.2018 18:45, Lennert Buytenhek пишет: > Hello! > > FS_IOC_FIEMAP on btrfs seems to be returning fe_physical values that > don't always correspond to the actual on-disk data locations. For some > files the values match, but e.g. for this file: > > # filefrag -v foo > Filesystem type is: 9123683e > File size of foo is 4096 (1 block of 4096 bytes) > ext: logical_offset: physical_offset: length: expected: flags: > 0: 0.. 0: 5774454.. 5774454: 1: last,eof > foo: 1 extent found > # > > The file data is actually on disk not in block 5774454 (0x581c76), but > in block 6038646 (0x5c2476), an offset of +0x40800. Is this expected > behavior? Googling didn't turn up much, apologies if this is an FAQ. :( > > (This is on 4.18.16-200.fc28.x86_64, the current Fedora 28 kernel.) >
My understanding is that it returns logical block address in btrfs address space. btrfs can span multiple devices so you will need to convert extent address to (device,offset) pair if necessary.
