Re: Bug or feature? logical_to_ino skips inodes with offset mismatch

[Hans van Kranenburg <hans.van.kranenburg@mendix.com>]

On 02/05/2017 10:54 PM, Hans van Kranenburg wrote:
> I was playing around with logical_to_ino and also implemented calling
> ino_lookup today to create a program that will print all data extents in
> a block group, and their related inodes and at least one filename per inode.
> 
> https://github.com/knorrie/python-btrfs/commits/develop
> See "examples: show filenames for data extents"
> 
> I ran into the following behaviour of logical_to_ino:
> 
> If the offset value in a backreference of an extent_item does not match
> the offset value of the extent_data object in the fs tree,
> logical_to_ino will skip the inode that uses data from the extent, and
> not report it.

Ah, wait... To answer my own question... The reason is probably because
the data at that exact place is not actually in use.

-# btrfs inspect-internal logical-resolve 336064511 . (+ 16KiB - 1)
-# btrfs inspect-internal logical-resolve 336064512 . (+ 16KiB)
./vmlinuz-4.9.0-1-amd64
-# btrfs inspect-internal logical-resolve 336064513 .
./vmlinuz-4.9.0-1-amd64

Jups... Makes sense.

But, it also means that I cannot use logical_to_ino as a helper to
expand shared backrefs to actual inode info... Meh.

-- 
Hans van Kranenburg