On Fri, Aug 30, 2019 at 01:36:11PM +0200, Johannes Thumshirn wrote:
> From: David Sterba <dsterba@xxxxxxxx>
I did not write the patch.
> Export supported checksum algorithms via sysfs.
>
> Signed-off-by: David Sterba <dsterba@xxxxxxxx>
> Signed-off-by: Johannes Thumshirn <jthumshirn@xxxxxxx>
And 'git am' complains that there are two s-o-b lines.
> Reviewed-by: Nikolay Borisov <nborisov@xxxxxxxx>
>
> ---
> Changes to v2:
> - Prevent possible overflow of sysfs attribute
> Changes to v1:
> - Removed btrfs_checksums_store() function (Nik)
> - Renamed sysfs file to supported_checksums
> ---
> fs/btrfs/sysfs.c | 29 +++++++++++++++++++++++++++++
> 1 file changed, 29 insertions(+)
>
> diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
> index f6d3c80f2e28..cae9c99253c7 100644
> --- a/fs/btrfs/sysfs.c
> +++ b/fs/btrfs/sysfs.c
> @@ -246,6 +246,24 @@ static umode_t btrfs_feature_visible(struct kobject *kobj,
> return mode;
> }
>
> +static ssize_t btrfs_supported_checksums_show(struct kobject *kobj,
> + struct kobj_attribute *a,
> + char *buf)
> +{
> + ssize_t ret = 0;
> + int i;
> +
> + for (i = 0; i < ARRAY_SIZE(btrfs_csums); i++) {
We'll need one more helper to return the number of csums, btrfs_csums is
not visible in sysfs.c anymore (aka it does not compile).
> + ret += snprintf(buf + ret, PAGE_SIZE - ret, "%s%s",
> + (i == 0 ? "" : ", "),
I've checked some sysfs files what's commonly used for a value separator
and there are more examples of ' ', though ', ' is also there. I'd
prefer to use a single letter separator.
> + btrfs_csums[i].name);
> +
> + }
> +
> + ret += snprintf(buf + ret, PAGE_SIZE - ret, "\n");
> + return ret;
> +}
> +
> BTRFS_FEAT_ATTR_INCOMPAT(mixed_backref, MIXED_BACKREF);
> BTRFS_FEAT_ATTR_INCOMPAT(default_subvol, DEFAULT_SUBVOL);
> BTRFS_FEAT_ATTR_INCOMPAT(mixed_groups, MIXED_GROUPS);
> @@ -259,6 +277,14 @@ BTRFS_FEAT_ATTR_INCOMPAT(no_holes, NO_HOLES);
> BTRFS_FEAT_ATTR_INCOMPAT(metadata_uuid, METADATA_UUID);
> BTRFS_FEAT_ATTR_COMPAT_RO(free_space_tree, FREE_SPACE_TREE);
>
> +static struct btrfs_feature_attr btrfs_attr_features_checksums_name = {
> + .kobj_attr = __INIT_KOBJ_ATTR(supported_checksums, S_IRUGO,
> + btrfs_supported_checksums_show,
> + NULL),
> + .feature_set = FEAT_INCOMPAT,
> + .feature_bit = 0,
> +};
> +
> static struct attribute *btrfs_supported_feature_attrs[] = {
> BTRFS_FEAT_ATTR_PTR(mixed_backref),
> BTRFS_FEAT_ATTR_PTR(default_subvol),
> @@ -272,6 +298,9 @@ static struct attribute *btrfs_supported_feature_attrs[] = {
> BTRFS_FEAT_ATTR_PTR(no_holes),
> BTRFS_FEAT_ATTR_PTR(metadata_uuid),
> BTRFS_FEAT_ATTR_PTR(free_space_tree),
> +
> + &btrfs_attr_features_checksums_name.kobj_attr.attr,
This belongs to the static features, ie. the same scheme as
rmdir_subvol. The two lists are merged together in sysfs directory, but
should be defined separately as they represent different type of
features.
> +
> NULL
> };
>
> --
> 2.16.4
