Re: [PATCH] xfsrestore: use utimensat() to provide atime/mtime with ns resolution

From: Eric Sandeen <sandeen@sandeen.net>
To: Brian Foster <bfoster@redhat.com>, xfs@oss.sgi.com
Subject: Re: [PATCH] xfsrestore: use utimensat() to provide atime/mtime with ns resolution
Date: Thu, 04 Sep 2014 14:47:00 -0500	[thread overview]
Message-ID: <5408C1B4.1010001@sandeen.net> (raw)
In-Reply-To: <1409848708-42666-1-git-send-email-bfoster@redhat.com>

On 9/4/14, 11:38 AM, Brian Foster wrote:
> xfsdump encodes and stores the full atime and mtime for each file with
> nanosecond resolution. xfsrestore uses utime() to set the times of each
> file that is restored. The latter supports resolution of 1 second, thus
> sub-second timestamp data is lost on restore.
>
> Add the associated configure checks for and use utimensat() when
> available to restore timestamps with nanosecond resolution. Create a new
> helper to facilitate conditional support for utimensat().
>
> Signed-off-by: Brian Foster <bfoster@redhat.com>
> ---
>
> I'm not totally sure on the configure bits here... it's mostly copied
> from xfsprogs and tweaked appropriately. It seems to work, at least. ;)
>
> Brian
>
>   configure.ac          |  2 ++
>   include/builddefs.in  |  1 +
>   m4/Makefile           |  1 +
>   m4/package_libcdev.m4 | 16 ++++++++++++++++
>   restore/Makefile      |  4 ++++
>   restore/content.c     | 38 ++++++++++++++++++++++++++++++--------
>   6 files changed, 54 insertions(+), 8 deletions(-)
>   create mode 100644 m4/package_libcdev.m4
>
> diff --git a/configure.ac b/configure.ac
> index 59f9564..28e604e 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -82,6 +82,8 @@ AC_PACKAGE_NEED_ATTRIBUTES_H
>   AC_PACKAGE_NEED_ATTRIBUTES_MACROS
>   AC_PACKAGE_NEED_ATTRGET_LIBATTR
>
> +AC_HAVE_UTIMENSAT
> +
>   AC_MANUAL_FORMAT
>
>   AC_CONFIG_FILES([include/builddefs])
> diff --git a/include/builddefs.in b/include/builddefs.in
> index 269c928..bdf0ede 100644
> --- a/include/builddefs.in
> +++ b/include/builddefs.in
> @@ -69,6 +69,7 @@ ENABLE_SHARED	= @enable_shared@
>   ENABLE_GETTEXT	= @enable_gettext@
>
>   HAVE_ZIPPED_MANPAGES = @have_zipped_manpages@
> +HAVE_UTIMENSAT = @have_utimensat@
>
>   GCCFLAGS = -funsigned-char -fno-strict-aliasing -Wall
>   #	   -Wbitwise -Wno-transparent-union -Wno-old-initializer -Wno-decl
> diff --git a/m4/Makefile b/m4/Makefile
> index 9a35056..ae452f7 100644
> --- a/m4/Makefile
> +++ b/m4/Makefile
> @@ -16,6 +16,7 @@ LSRCFILES = \
>   	manual_format.m4 \
>   	package_attrdev.m4 \
>   	package_globals.m4 \
> +	package_libcdev.m4 \
>   	package_ncurses.m4 \
>   	package_pthread.m4 \
>   	package_utilies.m4 \
> diff --git a/m4/package_libcdev.m4 b/m4/package_libcdev.m4
> new file mode 100644
> index 0000000..6fcbdba
> --- /dev/null
> +++ b/m4/package_libcdev.m4
> @@ -0,0 +1,16 @@
> +#
> +# Check if we have a utimensat libc call
> +#
> +AC_DEFUN([AC_HAVE_UTIMENSAT],
> +  [ AC_MSG_CHECKING([for utimensat])
> +    AC_TRY_COMPILE([

(as discussed on IRC...)

I think you need AC_TRY_LINK here; changing utimensat() to utimensatFOO() still
passes.  ;)

-Eric

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