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

[Sidong Yang <realwakka@gmail.com>]

On Thu, Aug 19, 2021 at 02:05:52PM +0800, Qu Wenruo wrote:
> 
> 
> On 2021/8/19 下午2:03, Qu Wenruo wrote:
> > 
> > 
> > On 2021/8/18 上午8:38, 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
> > 
> > Could you give an example which includes both real (non-hole) extents
> > and real extents (better to include regular, compressed, preallocated
> > and inline).
> 
> Tons of typos... I mean to include both holes (like the existing
> example) and non-holes extents...

Sorry, I had no idea about holes. But I found some test code in
xfstests. It helpes me to make hole in file.

xfs_io -c "fpunch 96K 32K" /mnt/a/foobar
xfs_io -c "fpunch 64K 128K" /mnt/a/foobar

and the example is below.

# ./btrfs inspect dump-file-extent /mnt/a/foobar 
type = regular, start = 0, len = 98304, disk_bytenr = 21651456,
disk_num_bytes = 4096, offset = 0, compression = zstd
type = regular, start = 98304, len = 32768, disk_bytenr = 0,
disk_num_bytes = 0, offset = 0, compression = none

I'm afaid that I understand your request correctly. Is it what you want?
> 
> > 
> > Currently the output only contains holes, and for holes, a lot of
> > members makes no sense, like disk_bytenr/disk_num_bytes/offset (even it
> > can be non-zero) and compression.
> > 
> > Thanks,
> > Qu
> > 
> > > 
> > > Thanks,
> > > Sidong
> > >