bug#61386: [PATCH] cp,mv,install: Disable sparse copy on macOS

[Pádraig Brady]

On 09/02/2023 09:20, George Valkov wrote:
> Due to a bug in macOS, sparse copies are corrupted on virtual disks
> formatted with APFS. HFS is not affected. Affected are coreutils
> install, and gcp when compiled with SEEK_HOLE, as well as macOS Finder.
>
> While reading the entire file returns valid data, scanning for
> allocated segments may return holes where valid data is present.
> In this case a sparse copy does not contain these segments and returns
> zeroes instead. Once the virtual disk is dismounted and then
> mounted again, a sparse copy produces correct results.
>
> This breaks OpenWRT build on macOS. Details:
> https://github.com/openwrt/openwrt/pull/11960
> https://github.com/openwrt/openwrt/pull/11960#issuecomment-1423185579
>
> Signed-off-by: Georgi Valkov <gvalkov@gmail.com>
> ---
>   src/copy.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/src/copy.c b/src/copy.c
> index e16fedb28..4f56138a6 100644
> --- a/src/copy.c
> +++ b/src/copy.c
> @@ -1065,7 +1065,7 @@ infer_scantype (int fd, struct stat const *sb,
>         return PLAIN_SCANTYPE;
>       }
>   
> -#ifdef SEEK_HOLE
> +#if defined(SEEK_HOLE) && !defined(__APPLE__)
>     scan_inference->ext_start = lseek (fd, 0, SEEK_DATA);
>     if (0 <= scan_inference->ext_start || errno == ENXIO)
>       return LSEEK_SCANTYPE;


Thanks for the detailed report.
The patch might very well be appropriate.
We avoided copy_file_range() for a long time on Linux for example
until it became usable.

Thanks for confirming the latest git is also impacted.

I see you're on macOS 12.
macOS 13 supports fclonefileat() which may
avoid the issue, or also be impacted?

I wonder might an fdatasync(fd) avoid your issue,
which we might do if defined(__APPLE__)?

cheers,
Pádraig