/bin/cp of sparse files broken in 3.6.0-0.362.g68c13dc92f65.x86_64?

[Brian Inglis]

On 2025-02-12 12:08, Corinna Vinschen via Cygwin wrote:
> On Feb 12 10:54, Brian Inglis via Cygwin wrote:
>> On 2025-02-12 10:30, Corinna Vinschen via Cygwin wrote:
>>> On Feb 12 17:32, Cedric Blancher via Cygwin wrote:
>>>> Checklist:
>>>> - Volume has FILE_SUPPORTS_SPARSE_FILES
>>>> - Cygwin mount has "sparse" option (mount Y: -o sparse,exec /cygdrive/y)
>>>> - source file has FILE_ATTRIBUTE_SPARSE_FILE set
>>>>
>>>> But  cp --sparse=auto ... or any other combination of --sparse does
>>>> copy holes, i.e. turns 500GB of hole into 500GB of data (zero bytes).
>>>>
>>>> echo "hello sparse file\n" >testcase17_sparse_begins_with_data && dd
>>>> if=/dev/null of=testcase17_sparse_begins_with_data oflag=append bs=1
>>>> count=1 seek=$((65536*512)) && echo "endoffile"
>>>>>> testcase17_sparse_begins_with_data
>>>
>>> Works for me:
>>>
>>> $ uname -r
>>> 3.6.0-0.362.g68c13dc92f65.x86_64
>>>
>>> $ pwd
>>> /home/corinna/tmp
>>>
>>> $ mount | grep tmp
>>> C:/cygwin64/home/corinna/tmp on /home/corinna/tmp type ntfs (binary,sparse,user,bind)
>>>
>>> $ echo "hello sparse file\n" >testcase17_sparse_begins_with_data && dd if=/dev/null of=testcase17_sparse_begins_with_data oflag=append bs=1 count=1 seek=$((65536*512)) && echo "endoffile" >>testcase17_sparse_begins_with_data
>>>
>>> $ ls -gGsh testcase17*
>>> 128K -rw----r--+ 1 33M Feb 12 18:22 testcase17_sparse_begins_with_data
>>>
>>> $ cp --sparse=auto testcase17_sparse_begins_with_data testcase17_sparse_begins_with_data.copy
>>>
>>> $ ls -gGsh testcase17*
>>> 128K -rw----r--+ 1 33M Feb 12 18:22 testcase17_sparse_begins_with_data
>>> 128K -rw----r--+ 1 33M Feb 12 18:23 testcase17_sparse_begins_with_data.copy
>>
>> Hi Corinna,
>>
>> Did you test using coreutils current stable 9.0, test 9.5, or both?
> 
> Tested with 9.0.
> 
> I just installed 9.5 and the result after cp --sparse=auto is the same:
> 
> $ cp --version | head -1
> cp (GNU coreutils) 9.5
> $ rm testcase17_sparse_begins_with_data.copy
> $ cp --sparse=auto testcase17_sparse_begins_with_data testcase17_sparse_begins_with_data.copy
> $ ls -gGsh testcase17*
> 128K -rw----r--+ 1 33M Feb 12 18:22 testcase17_sparse_begins_with_data
> 128K -rw----r--+ 1 33M Feb 12 20:01 testcase17_sparse_begins_with_data.copy

Thanks for testing and reporting results.

The build tests lead me to think that sparse files were not supported, so I need 
to figure out a way to add a sparse mount which works at home and on scallywag - 
used ${DISTDIR:-/var/cache}/ in another package so could add tmp to that, mkdir 
then mount -o ... `cygpath -m .../tmp` .../tmp - are any other commands required 
for setup other than mount?

-- 
Take care. Thanks, Brian Inglis              Calgary, Alberta, Canada

La perfection est atteinte                   Perfection is achieved
non pas lorsqu'il n'y a plus rien à ajouter  not when there is no more to add
mais lorsqu'il n'y a plus rien à retrancher  but when there is no more to cut
                                 -- Antoine de Saint-Exupéry