Re: [PATCH] safe_create_leading_directories: fix race that could give a false negative

From: Junio C Hamano <gitster@pobox.com>
Date: Mar 17, 2013, 06:26 UTC
Message-ID: <7v7gl6sfsg.fsf@alter.siamese.dyndns.org>
In-Reply-To: <1363462256-5823-1-git-send-email-stevenrwalter@gmail.com>

Steven Walter <stevenrwalter@gmail.com> writes:

Show 6 quoted lines

> If two processes are racing to create the same directory tree, they will
> both see that the directory doesn't exist, both try to mkdir(), and one
> of them will fail.  This is okay, as we only care that the directory
> gets created.  So, we add a check for EEXIST from mkdir, and continue if
> the directory now exists.
> ---

Thanks.  Please sign-off your patch.

Show 17 quoted lines

>  sha1_file.c |    7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/sha1_file.c b/sha1_file.c
> index 40b2329..c7b7fec 100644
> --- a/sha1_file.c
> +++ b/sha1_file.c
> @@ -123,6 +123,13 @@ int safe_create_leading_directories(char *path)
>  			}
>  		}
>  		else if (mkdir(path, 0777)) {
> +			if (errno == EEXIST) {
> +				/* We could be racing with another process to
> +				 * create the directory.  As long as the
> +				 * directory gets created, we don't care. */
> +				if (stat(path, &st) && S_ISDIR(st.st_mode))
> +					continue;

	/*
         * Nice explanation, but we try to format our
         * multi-line comments like this, slash-asterisk
         * and nothing else on the opening line, and
         * asterisk-slash and nothing else on the closing
         * line.
         */

Thanks.

> +			}
>  			*pos = '/';
>  			return -1;
>  		}