Re: [PATCH v4 2/2] btrfs-progs: cmds: Add subcommand that dumps file extents

[David Sterba <dsterba@suse.cz>]

On Wed, Aug 18, 2021 at 12:38:19AM +0000, Sidong Yang wrote:
> On Tue, Aug 17, 2021 at 03:30:22PM +0200, David Sterba wrote:
> > On Sun, Jul 18, 2021 at 06:46:01AM +0000, Sidong Yang wrote:
> > > This patch adds an subcommand in inspect-internal. It dumps file extents of
> > > the file that user provided. It helps to show the internal information
> > > about file extents comprise the file.
> > 
> > Do you have an example of the output? That's the most interesting part.
> > Thanks.
> 
> Thanks for reply.
> This is an example of the output below.
> 
> # ./btrfs inspect-internal dump-file-extent /mnt/test1
> type = regular, start = 2097152, len = 3227648, disk_bytenr = 0, disk_num_bytes = 0, offset = 0, compression = none
> type = regular, start = 5324800, len = 16728064, disk_bytenr = 0, disk_num_bytes = 0, offset = 0, compression = none
> type = regular, start = 22052864, len = 8486912, disk_bytenr = 0, disk_num_bytes = 0, offset = 0, compression = none
> type = regular, start = 30572544, len = 36540416, disk_bytenr = 0, disk_num_bytes = 0, offset = 0, compression = none
> type = regular, start = 67112960, len = 5299630080, disk_bytenr = 0, disk_num_bytes = 0, offset = 0, compression = none

This resembles a debugging output, something like we have for
tracepoints but I think this should be more human readable, with
possiblity of parsing by scripts/tools.

So to not just duplicate what filefrag or xfs_io -c fiemap do, we can
optionally enhance the information with the specifics of btrfs, like on
which devices the extents are, which compression is there etc. But the
basic output should be more or less like filefrag.