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

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

On 2021/8/19 下午11:27, Sidong Yang wrote:
> 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?

This example is much better.

But still, for holes, things like
disk_bytenr/disk_num_bytes/offset/compression makes no sense and can be
skipped.

Furthermore, for hole/prealloc they need extra type other than "regular"

Thanks,
Qu
>>
>>>
>>> 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
>>>>