Re: [RESEND][PATCH] xfs: add online uevent for mount operation

Darrick J. Wong
2017-08-24T17:10:35Z

On Thu, Aug 24, 2017 at 09:41:55PM +0800, Hou Tao wrote:
> It will be useful if there is a corresponding online uevent after
> a XFS filesystem has been mounted. A typical usage of the uevent
> is setting the error configuration for a specific XFS filesystem
> or all XFS filesystems by using udevd.
>
> The following is an example of udevd rule which will shutdown
> any XFS filesystem after the filesystem gets any IO error:
>
> ACTION=="online", SUBSYSTEM=="xfs", DEVPATH=="/fs/xfs/*", \
> RUN+="/bin/sh -c 'echo 0 > /sys%p/error/metadata/default/max_retries; \
> echo 0 > /sys%p/error/metadata/EIO/max_retries; \
> echo 0 > /sys%p/error/metadata/ENOSPC/max_retries; \
> echo 0 > /sys%p/error/metadata/ENODEV/max_retries'"
>
> Suggested-by: Dave Chinner <david@fromorbit.com>
> Signed-off-by: Hou Tao <houtao1@huawei.com>
> ---
> fs/xfs/xfs_super.c | 15 +++++++++++++++
> 1 file changed, 15 insertions(+)
>
> diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
> index 38aaacd..695fe85f 100644
> --- a/fs/xfs/xfs_super.c
> +++ b/fs/xfs/xfs_super.c
> @@ -1530,6 +1530,19 @@ xfs_destroy_percpu_counters(
> percpu_counter_destroy(&mp->m_fdblocks);
> }
>
> +static void
> +xfs_fs_uevent(
> + struct xfs_mount *mp,
> + enum kobject_action action)
> +{
> + int err;
> +
> + err = kobject_uevent(&mp->m_kobj.kobject, action);

It might be useful to send kobject_uevent_env so that we can squeeze in
things like the fs uuid for easier identification? I envision a
/etc/xfs/fs.conf file like this:

[903db5b1-82cd-4f26-8221-443a4ed0563a]
error.metadata.EIO.max_retries = 0
error.fail_at_unmount = 1
config.cowextsize = 1048576
config.inherit_noatime = 1

With a udev helper that uses the fsuuid to find the appropriate section
of the ini^Wconfig file and load the appropriate values into sysfs. If
we ever decide to expose more config knobs through sysfs then they'll
be automatically supported.

> + if (err)
> + xfs_notice(mp, "Sending XFS uevent %d got error %d",
> + action, err);
> +}
> +
> STATIC int
> xfs_fs_fill_super(
> struct super_block *sb,
> @@ -1667,6 +1680,8 @@ xfs_fs_fill_super(
> goto out_unmount;
> }
>
> + xfs_fs_uevent(mp, KOBJ_ONLINE);

That said, I wonder if we ought to move this discussion to fsdevel to
pull in any /other/ filesystems that have sysfs knobs that they might
like to be able to persist? ext4 has a bunch of tunables too...

--D

> +
> return 0;
>
> out_filestream_unmount:
> --
> 2.5.0
>
> --
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