Re: [PATCH] scripts: recordmcount: break hardlinks

From: Steven Rostedt <rostedt@goodmis.org>
To: Russell King <rmk+kernel@arm.linux.org.uk>
Cc: "Michal Marek" <mmarek@suse.cz>,
	"Thomas Petazzoni" <thomas.petazzoni@free-electrons.com>,
	"Måns Rullgård" <mans@mansr.com>, "Arnd Bergmann" <arnd@arndb.de>,
	linux-kbuild@vger.kernel.org, linux-arm-msm@vger.kernel.org,
	"Nicolas Pitre" <nico@fluxnic.net>,
	"Stephen Boyd" <sboyd@codeaurora.org>,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] scripts: recordmcount: break hardlinks
Date: Fri, 11 Dec 2015 09:31:25 -0500	[thread overview]
Message-ID: <20151211093125.50b72639@gandalf.local.home> (raw)
In-Reply-To: <E1a7MVT-0000et-62@rmk-PC.arm.linux.org.uk>

On Fri, 11 Dec 2015 12:09:03 +0000
Russell King <rmk+kernel@arm.linux.org.uk> wrote:

> recordmcount edits the file in-place, which can cause problems when
> using ccache in hardlink mode.  Arrange for recordmcount to break a
> hardlinked object.
> 
> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
> ---
> Steven, sorry it took a while to get this out...

Should this be for stable, or is it fine to just add this to my 4.5
queue?

-- Steve

> 
>  scripts/recordmcount.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/scripts/recordmcount.c b/scripts/recordmcount.c
> index 698768bdc581..91705ef30402 100644
> --- a/scripts/recordmcount.c
> +++ b/scripts/recordmcount.c
> @@ -211,6 +211,20 @@ static void *mmap_file(char const *fname)
>  		addr = umalloc(sb.st_size);
>  		uread(fd_map, addr, sb.st_size);
>  	}
> +	if (sb.st_nlink != 1) {
> +		/* file is hard-linked, break the hard link */
> +		close(fd_map);
> +		if (unlink(fname) < 0) {
> +			perror(fname);
> +			fail_file();
> +		}
> +		fd_map = open(fname, O_RDWR | O_CREAT, sb.st_mode);
> +		if (fd_map < 0) {
> +			perror(fname);
> +			fail_file();
> +		}
> +		uwrite(fd_map, addr, sb.st_size);
> +	}
>  	return addr;
>  }
>  