Re: [RFC PATCH 5/6] btrfs: add send_stream_version attribute to sysfs

[Omar Sandoval <osandov@osandov.com>]

On Tue, May 08, 2018 at 10:06:50PM -0400, Howard McLauchlan wrote:
> From: Filipe David Borba Manana <fdmanana@gmail.com>
> 
> So that applications can find out what's the highest send stream
> version supported/implemented by the running kernel:
> 
>     $ cat /sys/fs/btrfs/send/stream_version
>     2
> 
> [Howard: rebased on 4.17-rc4]
> Signed-off-by: Howard McLauchlan <hmclauchlan@fb.com>
> Signed-off-by: Filipe David Borba Manana <fdmanana@gmail.com>
> Reviewed-by: David Sterba <dsterba@suse.cz>
> ---
>  fs/btrfs/send.h  |  1 +
>  fs/btrfs/sysfs.c | 29 +++++++++++++++++++++++++++++
>  2 files changed, 30 insertions(+)
> 
> diff --git a/fs/btrfs/send.h b/fs/btrfs/send.h
> index a5830d216ac1..2f5e25e03def 100644
> --- a/fs/btrfs/send.h
> +++ b/fs/btrfs/send.h
> @@ -12,6 +12,7 @@
>  #define BTRFS_SEND_STREAM_MAGIC "btrfs-stream"
>  #define BTRFS_SEND_STREAM_VERSION_1 1
>  #define BTRFS_SEND_STREAM_VERSION_2 2
> +#define BTRFS_SEND_STREAM_VERSION_LATEST BTRFS_SEND_STREAM_VERSION_2
>  
>  #define BTRFS_SEND_BUF_SIZE SZ_64K
>  #define BTRFS_SEND_READ_SIZE (48 * SZ_1K)
> diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
> index 4848a4318fb5..3c82cba91ff6 100644
> --- a/fs/btrfs/sysfs.c
> +++ b/fs/btrfs/sysfs.c
> @@ -18,6 +18,7 @@
>  #include "transaction.h"
>  #include "sysfs.h"
>  #include "volumes.h"
> +#include "send.h"
>  
>  static inline struct btrfs_fs_info *to_fs_info(struct kobject *kobj);
>  static inline struct btrfs_fs_devices *to_fs_devs(struct kobject *kobj);
> @@ -884,6 +885,28 @@ static int btrfs_init_debugfs(void)
>  	return 0;
>  }
>  
> +static ssize_t send_stream_version_show(struct kobject *kobj,
> +					struct kobj_attribute *a,
> +					char *buf)
> +{
> +	return snprintf(buf, PAGE_SIZE, "%d\n",
> +			BTRFS_SEND_STREAM_VERSION_LATEST);
> +}
> +
> +BTRFS_ATTR(, stream_version, send_stream_version_show);
> +
> +static struct attribute *btrfs_send_attrs[] = {
> +	BTRFS_ATTR_PTR(, stream_version),
> +	NULL
> +};
> +
> +static const struct attribute_group btrfs_send_attr_group = {
> +	.name = "send",
> +	.attrs = btrfs_send_attrs,
> +};
> +
> +
> +

I know this is Filipe's code, but there are two extra newlines there ;)
Otherwise, assuming you tested this and it works as advertised,

Reviewed-by: Omar Sandoval <osandov@fb.com>

>  int __init btrfs_init_sysfs(void)
>  {
>  	int ret;
> @@ -900,8 +923,13 @@ int __init btrfs_init_sysfs(void)
>  	ret = sysfs_create_group(&btrfs_kset->kobj, &btrfs_feature_attr_group);
>  	if (ret)
>  		goto out2;
> +	ret = sysfs_create_group(&btrfs_kset->kobj, &btrfs_send_attr_group);
> +	if (ret)
> +		goto out3;
>  
>  	return 0;
> +out3:
> +	sysfs_remove_group(&btrfs_kset->kobj, &btrfs_feature_attr_group);
>  out2:
>  	debugfs_remove_recursive(btrfs_debugfs_root_dentry);
>  out1:
> @@ -913,6 +941,7 @@ int __init btrfs_init_sysfs(void)
>  void __cold btrfs_exit_sysfs(void)
>  {
>  	sysfs_remove_group(&btrfs_kset->kobj, &btrfs_feature_attr_group);
> +	sysfs_remove_group(&btrfs_kset->kobj, &btrfs_send_attr_group);
>  	kset_unregister(btrfs_kset);
>  	debugfs_remove_recursive(btrfs_debugfs_root_dentry);
>  }
> -- 
> 2.17.0
>