Re: [PATCH 2/2] relatime: Allow making relatime the default behaviour

[Randy Dunlap <randy.dunlap@oracle.com>]

Matthew Garrett wrote:
> Allow the kernel to enable relatime on all mounts by default. This can 
> be configured at build time or by a kernel parameter or sysctl. Also add 
> an MS_NORELATIME mount option to allow the default to be overridden for 
> specific mount points.
> 
> Signed-off-by: Matthew Garrett <mjg@redhat.com>
> 
> ---

Hi,

Please use diffstat for all (non-trivial) patches.
or whatever git calls it.

Comments below...

> Updated version of Ingo's patch, but adds MS_NORELATIME. util-linux will 
> need updating to match if this is merged.
> 
> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
> index e0f346d..eba3b07 100644
> --- a/Documentation/kernel-parameters.txt
> +++ b/Documentation/kernel-parameters.txt
> @@ -616,6 +616,10 @@ and is between 256 and 4096 characters. It is defined in the file
>  			This is a 16-member array composed of values
>  			ranging from 0-255.
>  
> +	default_relatime=
> +			[FS] mount all filesystems with relative atime
> +			updates by default.
> +

I had rather see it called "relatime_default" fwiw.

>  	vt.default_utf8=
>  			[VT]
>  			Format=<0|1>
> @@ -1847,6 +1851,10 @@ and is between 256 and 4096 characters. It is defined in the file
>  			[KNL, SMP] Set scheduler's default relax_domain_level.
>  			See Documentation/cpusets.txt.
>  
> +	relatime_interval=
> +			[FS] relative atime update frequency, in seconds.
> +			(default: 1 day: 86400 seconds)
> +
>  	reserve=	[KNL,BUGS] Force the kernel to ignore some iomem area
>  
>  	reservetop=	[X86-32]
> diff --git a/fs/Kconfig b/fs/Kconfig
> index 522469a..fcd3d48 100644
> --- a/fs/Kconfig
> +++ b/fs/Kconfig
> @@ -1546,6 +1546,29 @@ config 9P_FS
>  
>  endif # NETWORK_FILESYSTEMS
>  
> +config DEFAULT_RELATIME
> +	bool "Mount all filesystems with relatime by default"
> +	default y
> +	help
> +	  If you say Y here, all your filesystems will be mounted
> +	  with the "relatime" mount option. This eliminates many atime
> +	  ('file last accessed' timestamp) updates (which otherwise
> +	  is performed on every file access and generates a write
> +	  IO to the inode) and thus speeds up IO. Atime is still updated,
> +	  but only once per day.
> +
> +	  The mtime ('file last modified') and ctime ('file created')
> +	  timestamp are unaffected by this change.
> +
> +	  Use the "norelatime" kernel boot option to turn off this
> +	  feature.
> +
> +config DEFAULT_RELATIME_VAL
> +	int
> +	default "1" if DEFAULT_RELATIME
> +	default "0"
> +
> +
>  if BLOCK
>  menu "Partition Types"
>  
> diff --git a/fs/inode.c b/fs/inode.c
> index 348fa16..51e9ae1 100644
> --- a/fs/inode.c
> +++ b/fs/inode.c
> @@ -1185,6 +1185,17 @@ EXPORT_SYMBOL(bmap);
>  int relatime_interval __read_mostly = 24*60*60;
>  
>  /*
> + * Allow overriding the default relatime value on the kernel command line
> + */
> +static int __init set_relatime_interval(char *str)
> +{
> +	get_option(&str, &relatime_interval);
> +
> +	return 1;
> +}
> +__setup("relatime_interval=", set_relatime_interval);
> +
> +/*
>   * With relative atime, only update atime if the
>   * previous atime is earlier than either the ctime or
>   * mtime.
> diff --git a/fs/namespace.c b/fs/namespace.c
> index 65b3dc8..76f30b5 100644
> --- a/fs/namespace.c
> +++ b/fs/namespace.c
> @@ -1883,6 +1883,24 @@ int copy_mount_options(const void __user * data, unsigned long *where)
>  }
>  
>  /*
> + * Allow users to disable (or enable) atime updates via a .config
> + * option or via the boot line, or via /proc/sys/fs/default_relatime:
> + */
> +int default_relatime __read_mostly = CONFIG_DEFAULT_RELATIME_VAL;
> +
> +static int __init set_default_relatime(char *str)
> +{
> +	get_option(&str, &default_relatime);
> +
> +	printk(KERN_INFO "Mount all filesystems with"

missing a space between "with" and "default".

> +		"default relative atime updates: %s.\n",
> +		default_relatime ? "enabled" : "disabled");
> +
> +	return 1;
> +}
> +__setup("default_relatime=", set_default_relatime);
> +
> +/*
>   * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
>   * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
>   *
> @@ -1930,6 +1948,11 @@ long do_mount(char *dev_name, char *dir_name, char *type_page,
>  		mnt_flags |= MNT_NODIRATIME;
>  	if (flags & MS_RELATIME)
>  		mnt_flags |= MNT_RELATIME;
> +	else if (default_relatime &&
> +		 !(flags & (MS_NOATIME | MS_NODIRATIME | MS_NORELATIME))) {
> +		mnt_flags |= MNT_RELATIME;
> +		flags |= MS_RELATIME;
> +	}
>  	if (flags & MS_RDONLY)
>  		mnt_flags |= MNT_READONLY;
>  
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 0dcdd94..a4db010 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -135,6 +135,7 @@ extern int dir_notify_enable;
>  #define MS_RELATIME	(1<<21)	/* Update atime relative to mtime/ctime. */
>  #define MS_KERNMOUNT	(1<<22) /* this is a kern_mount call */
>  #define MS_I_VERSION	(1<<23) /* Update inode I_version field */
> +#define MS_NORELATIME	(1<<24)	/* Disable relatie even if the default */

                                                   relatime

>  #define MS_ACTIVE	(1<<30)
>  #define MS_NOUSER	(1<<31)



-- 
~Randy