Re: [PATCH] Add an option not to use link(src, dest) && unlink(src) when that is unreliable

From: Johannes Sixt <j6t@kdbg.org>
Date: Apr 23, 2009, 19:16 UTC
Message-ID: <200904232116.10769.j6t@kdbg.org>
In-Reply-To: <alpine.DEB.1.00.0904231252080.10279@pacific.mpi-cbg.de>

On Donnerstag, 23. April 2009, Johannes Schindelin wrote:

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> It seems that accessing NTFS partitions with ufsd (at least on my EeePC)
> has an unnerving bug: if you link() a file and unlink() it right away,
> the target of the link() will have the correct size, but consist of NULs.
>
> It seems as if the calls are simply not serialized correctly, as
> single-stepping through the function move_temp_to_file() works flawlessly.
>
> As ufsd is "Commertial software", I cannot fix it, and have to work

"commercial software"

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> around it in Git.
>
> At the same time, it seems that this fixes msysGit issues 222 and 229 to
> assume that Windows cannot handle link() && unlink().
>
> Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

...

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> @@ -2225,7 +2225,9 @@ int move_temp_to_file(const char *tmpfile, const char
> *filename) {
>  	int ret = 0;
>
> -	if (link(tmpfile, filename))
> +	if (unreliable_hardlinks)
> +		ret = ~EEXIST;

It took me a while to see why we need a tilde here, but it's ok. Perhaps this helps others:

+		ret = ~EEXIST;	/* anything but EEXIST */

Nevertheless:

Acked-by: Johannes Sixt <j6t@kdbg.org>

> +	else if (link(tmpfile, filename))
>  		ret = errno;

-- Hannes