ACK: [SRU][Xenial][Artful][Bionic][v2][PATCH 1/1] UBUNTU: SAUCE: (no-up) bcache: decouple emitting a cached_dev CHANGE uevent

[Colin Ian King]

On 11/12/17 14:12, Joseph Salisbury wrote:
> From: Ryan Harper <ryan.harper at canonical.com>
> 
> BugLink: http://bugs.launchpad.net/bugs/1729145
> 
> - decouple emitting a cached_dev CHANGE uevent which includes dev.uuid
>   and dev.label from bch_cached_dev_run() which only happens when a
>   bcacheX device is bound to the actual backing block device (bcache0 -> vdb)
> 
> - update bch_cached_dev_run() to invoke bch_cached_dev_emit_change() as
>   needed; no functional code path changes here
> 
> - Modify register_bcache to detect a re-registering of a bcache
>   cached_dev, and in that case call bcache_cached_dev_emit_change() to
> 
> Signed-off-by: Ryan Harper <ryan.harper at canonical.com>
> Signed-off-by: Joseph Salisbury <joseph.salisbury at canonical.com>
> ---
>  drivers/md/bcache/bcache.h |  1 +
>  drivers/md/bcache/super.c  | 53 +++++++++++++++++++++++++++++++++++++---------
>  2 files changed, 44 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
> index 02619ca..8ed7e7a 100644
> --- a/drivers/md/bcache/bcache.h
> +++ b/drivers/md/bcache/bcache.h
> @@ -906,6 +906,7 @@ int bch_flash_dev_create(struct cache_set *c, uint64_t size);
>  
>  int bch_cached_dev_attach(struct cached_dev *, struct cache_set *);
>  void bch_cached_dev_detach(struct cached_dev *);
> +void bch_cached_dev_emit_change(struct cached_dev *);
>  void bch_cached_dev_run(struct cached_dev *);
>  void bcache_device_stop(struct bcache_device *);
>  
> diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
> index 04608da..9ff0aac 100644
> --- a/drivers/md/bcache/super.c
> +++ b/drivers/md/bcache/super.c
> @@ -834,7 +834,7 @@ static void calc_cached_dev_sectors(struct cache_set *c)
>  	c->cached_dev_sectors = sectors;
>  }
>  
> -void bch_cached_dev_run(struct cached_dev *dc)
> +void bch_cached_dev_emit_change(struct cached_dev *dc)
>  {
>  	struct bcache_device *d = &dc->disk;
>  	char buf[SB_LABEL_SIZE + 1];
> @@ -849,9 +849,18 @@ void bch_cached_dev_run(struct cached_dev *dc)
>  	buf[SB_LABEL_SIZE] = '\0';
>  	env[2] = kasprintf(GFP_KERNEL, "CACHED_LABEL=%s", buf);
>  
> +	/* won't show up in the uevent file, use udevadm monitor -e instead
> +	 * only class / kset properties are persistent */
> +	kobject_uevent_env(&disk_to_dev(d->disk)->kobj, KOBJ_CHANGE, env);
> +	kfree(env[1]);
> +	kfree(env[2]);
> +
> +}
> +
> +void bch_cached_dev_run(struct cached_dev *dc)
> +{
> +	struct bcache_device *d = &dc->disk;
>  	if (atomic_xchg(&dc->running, 1)) {
> -		kfree(env[1]);
> -		kfree(env[2]);
>  		return;
>  	}
>  
> @@ -867,11 +876,9 @@ void bch_cached_dev_run(struct cached_dev *dc)
>  
>  	add_disk(d->disk);
>  	bd_link_disk_holder(dc->bdev, dc->disk.disk);
> -	/* won't show up in the uevent file, use udevadm monitor -e instead
> -	 * only class / kset properties are persistent */
> -	kobject_uevent_env(&disk_to_dev(d->disk)->kobj, KOBJ_CHANGE, env);
> -	kfree(env[1]);
> -	kfree(env[2]);
> +
> +	/* emit change event */
> +	bch_cached_dev_emit_change(dc);
>  
>  	if (sysfs_create_link(&d->kobj, &disk_to_dev(d->disk)->kobj, "dev") ||
>  	    sysfs_create_link(&disk_to_dev(d->disk)->kobj, &d->kobj, "bcache"))
> @@ -1916,6 +1923,21 @@ static bool bch_is_open_backing(struct block_device *bdev) {
>  	return false;
>  }
>  
> +static struct cached_dev *bch_find_cached_dev(struct block_device *bdev) {
> +	struct cache_set *c, *tc;
> +	struct cached_dev *dc, *t;
> +
> +	list_for_each_entry_safe(c, tc, &bch_cache_sets, list)
> +		list_for_each_entry_safe(dc, t, &c->cached_devs, list)
> +			if (dc->bdev == bdev)
> +				return dc;
> +	list_for_each_entry_safe(dc, t, &uncached_devices, list)
> +		if (dc->bdev == bdev)
> +			return dc;
> +
> +	return NULL;
> +}
> +
>  static bool bch_is_open_cache(struct block_device *bdev) {
>  	struct cache_set *c, *tc;
>  	struct cache *ca;
> @@ -1941,6 +1963,7 @@ static ssize_t register_bcache(struct kobject *k, struct kobj_attribute *attr,
>  	struct cache_sb *sb = NULL;
>  	struct block_device *bdev = NULL;
>  	struct page *sb_page = NULL;
> +	struct cached_dev *dc = NULL;
>  
>  	if (!try_module_get(THIS_MODULE))
>  		return -EBUSY;
> @@ -1957,10 +1980,20 @@ static ssize_t register_bcache(struct kobject *k, struct kobj_attribute *attr,
>  		if (bdev == ERR_PTR(-EBUSY)) {
>  			bdev = lookup_bdev(strim(path), 0);
>  			mutex_lock(&bch_register_lock);
> -			if (!IS_ERR(bdev) && bch_is_open(bdev))
> +			if (!IS_ERR(bdev) && bch_is_open(bdev)) {
>  				err = "device already registered";
> -			else
> +				/* emit CHANGE event for backing devices to export
> +				 * CACHED_{UUID/LABEL} values to udev */
> +				if (bch_is_open_backing(bdev)) {
> +					dc = bch_find_cached_dev(bdev);
> +					if (dc) {
> +						bch_cached_dev_emit_change(dc);
> +						err = "device already registered (emitting change event)";
> +					}
> +				}
> +			} else {
>  				err = "device busy";
> +            }
>  			mutex_unlock(&bch_register_lock);
>  			if (!IS_ERR(bdev))
>  				bdput(bdev);
> 

Positive test results for Bionic. Looks reasonable to me.

Will this be sent upstream at some point?

Acked-by: Colin Ian King <colin.king at canonical.com>