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bug#14618: Erroneous sparse copy command results in empty file
From: |
Pádraig Brady |
Subject: |
bug#14618: Erroneous sparse copy command results in empty file |
Date: |
Fri, 14 Jun 2013 21:03:52 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130110 Thunderbird/17.0.2 |
On 06/14/2013 12:35 PM, Koen De Wit wrote:
> When trying to create a sparse copy of a file on a different filesystem you
> get an "Invalid cross-device link" error, as expected. However, an empty file
> is created instead of the sparse copy:
As a side note, sparse copying is a separate thing to reflinking.
> # mkfs.btrfs -f /dev/sde1
> # mkfs.btrfs -f /dev/sde2
> # mount /dev/sde1 /mnt/part1
> # mount /dev/sde2 /mnt/part2
> # echo "abc" > /mnt/part1/testfile
> # ./cp --reflink /mnt/part1/testfile /mnt/part2/testcopy
> ./cp: failed to clone ‘/mnt/part2/testcopy’ from ‘/mnt/part1/testfile’:
> Invalid cross-device link
> # ls -la /mnt/part1/testfile
> -rw-r--r--. 1 root root 4 Jun 14 14:49 /mnt/part1/testfile
> # ls -la /mnt/part2/testcopy
> -rw-r--r--. 1 root root 0 Jun 14 14:49 /mnt/part2/testcopy
>
> The same occurs when trying to create a sparse copy on a filesystem that does
> not support sparse copies:
>
> # mkfs.ext3 /dev/sde1
> # mount /dev/sde1 /mnt/part1
> # echo "abc" > /mnt/part1/testfile
> # ./cp --reflink /mnt/part1/testfile /mnt/part1/testcopy
> ./cp: failed to clone ‘/mnt/part1/testcopy’ from ‘/mnt/part1/testfile’:
> Inappropriate ioctl for device
> # ls -la /mnt/part1
> (...)
> -rw-r--r--. 1 root root 0 Jun 14 14:58 testcopy
> -rw-r--r--. 1 root root 4 Jun 14 14:58 testfile
>
> If creating a sparse copy fails, no file should be created.
>
> ln treats this error in the right way:
>
> # ln /mnt/part1/testfile /mnt/part2/testlink
> ln: creating hard link `/mnt/part2/testlink' => `/mnt/part1/testfile':
> Invalid cross-device link
> # ls -la /mnt/part2/testlink
> ls: cannot access /mnt/part2/testlink: No such file or directory
>
> Tested with coreutils today's git HEAD and kernel 3.9.5.
This was discussed previously:
http://lists.gnu.org/archive/html/coreutils/2013-03/msg00056.html
Summary of that is that it may be best handled outside of cp.
cheers,
Pádraig.