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Date: Wed, 12 Feb 2025 18:30:24 +0100
To: cygwin AT cygwin DOT com
Subject: Re: /bin/cp of sparse files broken in
 3.6.0-0.362.g68c13dc92f65.x86_64?
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From: Corinna Vinschen via Cygwin <cygwin AT cygwin DOT com>
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On Feb 12 17:32, Cedric Blancher via Cygwin wrote:
> Good afternoon!
> 
> Is copying sparse files broken in 3.6.0-0.362.g68c13dc92f65.x86_64?
> 
> cp --version
> cp (GNU coreutils) 9.5
> Packaged by Cygwin (9.5-1
> 
> 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


Corinna

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