linux-ext4 - Re: [PATCH 1/4] FS: filesystem corruption notification

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Message-Id: <20090603115810.10641330.akpm@linux-foundation.org>
Date:	Wed, 3 Jun 2009 11:58:10 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Denis Karpov <ext-denis.2.karpov@...ia.com>
Cc:	axboe@...nel.dk, hirofumi@...l.parknet.co.jp,
	linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org, adrian.hunter@...ia.com,
	artem.bityutskiy@...ia.com
Subject: Re: [PATCH 1/4] FS: filesystem corruption notification

On Wed,  3 Jun 2009 18:05:15 +0300
Denis Karpov <ext-denis.2.karpov@...ia.com> wrote:

> Add a generic mechnism to notify the userspace about possible filesystem
> corruption through sysfs entry (/sys/block/<bdev>/<part>/fs_unclean)
> and uevent (KOBJ_CHANGE, uevent's environment variable FS_UNCLEAN=[0:1]).
> 
> To mark fs clean (e.g. after fs was fixed by userspace):
> 
> echo 0 > /sys/block/<bdev>/<part>/fs_unclean
> (you will still receive uevent KOBJ_CHANGE with env var FS_UNCLEAN=0)
> 
> Signed-off-by: Denis Karpov <ext-denis.2.karpov@...ia.com>
> ---
>  fs/partitions/check.c |   42 ++++++++++++++++++++++++++++++++++++++++++
>  include/linux/genhd.h |    2 ++
>  2 files changed, 44 insertions(+), 0 deletions(-)
> 
> diff --git a/fs/partitions/check.c b/fs/partitions/check.c
> index 99e33ef..191d89e 100644
> --- a/fs/partitions/check.c
> +++ b/fs/partitions/check.c
> @@ -196,6 +196,24 @@ check_partition(struct gendisk *hd, struct block_device *bdev)
>  	return ERR_PTR(res);
>  }
>  
> +void notify_part_fs_unclean(struct device *dev, uint8_t unclean)
> +{
> +	char event_string[13];
> +	char *envp[] = { event_string, NULL };
> +
> +	if ((unclean != 0 && unclean != 1) ||
> +		unclean == dev_to_part(dev)->fs_unclean)
> +		return;
> +
> +	dev_to_part(dev)->fs_unclean = unclean;
> +
> +	sysfs_notify(&dev->kobj, NULL, "fs_unclean");
> +
> +	sprintf(event_string, "FS_UNCLEAN=%u", unclean);
> +	kobject_uevent_env(&dev->kobj, KOBJ_CHANGE, envp);
> +}
> +EXPORT_SYMBOL(notify_part_fs_unclean);

Please document this function.

That documentation should, amongst other things, explain the semantics
of the `unclean' argument.  It can be 0, 1 or "something else".  Why?

Also, why is `unclean' a u8 rather than a boring old `int'?

>  static ssize_t part_partition_show(struct device *dev,
>  				   struct device_attribute *attr, char *buf)
>  {
> @@ -246,6 +264,26 @@ ssize_t part_stat_show(struct device *dev,
>  		jiffies_to_msecs(part_stat_read(p, time_in_queue)));
>  }
>  
> +ssize_t part_fs_unclean_show(struct device *dev,
> +		       struct device_attribute *attr, char *buf)
> +{
> +	struct hd_struct *p = dev_to_part(dev);
> +
> +	return sprintf(buf, "%d\n", p->fs_unclean);
> +}
> +
> +ssize_t part_fs_unclean_store(struct device *dev,
> +			struct device_attribute *attr,
> +			const char *buf, size_t count)
> +{
> +	int i;
> +
> +	if (count > 0 && sscanf(buf, "%d", &i) > 0)

strict_strtoul(), please.

> +		notify_part_fs_unclean(dev, (i == 0) ? 0 : 1);
> +
> +	return count;
> +}

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