[PATCH] allow strictatime to be set as a global default

[Mandeep Sandhu]

Ah yes...now it makes sense! :)

The current 'word of caution' (about increased I/O load on block
devices), seems mild IMHO. Maybe we should we have a stricter
warning...something like enabling this option might be harmful to the
life of your block device (due to excessive writes) and will also lead
to reduced performance?

HTH,
-mandeep


On Fri, Dec 18, 2015 at 2:12 PM, Raymond Jennings <shentino at gmail.com> wrote:
> On Fri, Dec 18, 2015 at 10:50 AM, Mandeep Sandhu
> <mandeepsandhu.chd at gmail.com> wrote:
>>
>> You've removed the strictatime option altogether. So how does that
>> satisfy people who _do_ want it?
>
>
> ...actually it looks like I was an idiot and got my diff backwards when I
> pulled it out of git :P
>
> Here's the correct version.
>
> diff --git a/fs/Kconfig b/fs/Kconfig
> index 6ce72d8..4b917eb 100644
> --- a/fs/Kconfig
> +++ b/fs/Kconfig
> @@ -4,6 +4,17 @@
>
> menu "File systems"
>
> +config DEFAULT_STRICTATIME
> +       bool "Use strictatime by default"
> +       default n
> +       help
> +         Use strictatime as a default mount option.
> +
> +         Strictatime preserves ancient historic behavior of keeping the
> atime field always up to date.
> +         However, it was changed in 2007 to relatime to reduce I/O load on
> block devices.
> +
> +         If unsure, say N.
> +
> # Use unaligned word dcache accesses
> config DCACHE_WORD_ACCESS
>        bool
> diff --git a/fs/namespace.c b/fs/namespace.c
> index 0570729..48e7c15 100644
> --- a/fs/namespace.c
> +++ b/fs/namespace.c
> @@ -2680,9 +2680,15 @@ long do_mount(const char *dev_name, const char __user
> *dir_name,
>         if (retval)
>                 goto dput_out;
>
> -       /* Default to relatime unless overriden */
> +#ifdef CONFIG_DEFAULT_STRICTATIME
> +       /* Default to strictatime unless overridden */
> +       if (flags & MS_RELATIME)
> +               mnt_flags |= MNT_RELATIME;
> +#else
> +       /* Default to relatime unless overridden */
>         if (!(flags & MS_NOATIME))
>                 mnt_flags |= MNT_RELATIME;
> +#endif
>
>
>         /* Separate the per-mountpoint flags */
>         if (flags & MS_NOSUID)
>
>
>