Re: [patch] link.2: ERRORS: add ENOENT when target is deleted

["Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>]

On 11/25/20 2:27 PM, Mathias Rav wrote:
> Linux kernel commit aae8a97d3ec30788790d1720b71d76fd8eb44b73
> (part of kernel release v2.6.39) added a check to disallow creating a
> hardlink to an unlinked file.
> 
> Signed-off-by: Mathias Rav <m@git.strova.dk>

Thanks, Matthias. Patch applied.

> ---
> The manual page already describes the trick of using AT_SYMLINK_FOLLOW
> as an alternative to AT_EMPTY_PATH, and for AT_EMPTY_PATH the manual
> page already notes that it "will generally not work if the file has a
> link count of zero". However, the precise error (ENOENT) is not mentioned,
> and the error case isn't mentioned in the ERRORS section at all.
> 
> This makes it easy to overlook the fact that the AT_SYMLINK_FOLLOW
> trick on /proc/self/fd/NN won't work on deleted files, as evidenced by
> the follow message (which turns up when googling "linkat deleted ENOENT"):
> https://groups.google.com/g/linux.kernel/c/zZO4lqqwp64

I think the above piece is actually worth including in the
commit message, so I added it.

Thanks,

Michael

>  man2/link.2 | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/man2/link.2 b/man2/link.2
> index 1e7b2efd8..202119c6e 100644
> --- a/man2/link.2
> +++ b/man2/link.2
> @@ -318,6 +318,10 @@ open(path, O_TMPFILE | O_EXCL, mode);
>  .IP
>  See
>  .BR open (2).
> +.B ENOENT
> +An attempt was made to link to a
> +.I /proc/self/fd/NN
> +file corresponding to a file that has been deleted.
>  .TP
>  .B ENOENT
>  .I oldpath
> 


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/