Deletion of a subvolume by rmdir(2) has become allowed by the 'commit cd2decf640b1 ("btrfs: Allow rmdir(2) to delete an empty subvolume")'.
It is a kind of new feature and this commits add a sysfs entry /sys/fs/btrfs/features/rmdir_subvol to indicate the availability of the feature so that a user program (e.g. xfstests) can detect it. Prior to this commit, all entry in /sys/fs/btrfs/features is a feature which depends on feature bits of superblock (i.e. each feature affects on-disk format) and managed by attribute_group "btrfs_feature_attr_group". For each fs, entries in /sys/fs/btrfs/UUID/features indicate which features are enabled (or can be changed online) for the fs. However, rmdir_subvol feature only depends on kernel modules. Therefore new attribute_group "btrfs_static_feature_attr_group" is introduced and sysfs_merge_group() is used to share /sys/fs/btrfs/features directory. Features in "btrfs_static_feature_attr_group" won't be listed in each /sys/fs/btrfs/UUID/features. Signed-off-by: Tomohiro Misono <misono.tomoh...@jp.fujitsu.com> --- Hi David, Sorry for the misunderstanding. How about this version which uses /sys/fs/btrfs/features while using different attribute_group for static features. Thanks, fs/btrfs/sysfs.c | 37 +++++++++++++++++++++++++++++++++++++ 1 file changed, 37 insertions(+) diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c index 217d401fe8ae..ae6003b34c76 100644 --- a/fs/btrfs/sysfs.c +++ b/fs/btrfs/sysfs.c @@ -210,12 +210,40 @@ static struct attribute *btrfs_supported_feature_attrs[] = { NULL }; +/* + * Features which depend on feature bits and may differ between each fs. + * /sys/fs/btrfs/features lists all capable features of this kernel + * while /sys/fs/btrfs/UUID/features shows features of the fs which are + * enabled or can be changed online + */ static const struct attribute_group btrfs_feature_attr_group = { .name = "features", .is_visible = btrfs_feature_visible, .attrs = btrfs_supported_feature_attrs, }; +static ssize_t rmdir_subvol_show(struct kobject *kobj, + struct kobj_attribute *ka, char *buf) +{ + return snprintf(buf, PAGE_SIZE, "0\n"); +} +BTRFS_ATTR(static_feature, rmdir_subvol, rmdir_subvol_show); + +static struct attribute *btrfs_supported_static_feature_attrs[] = { + BTRFS_ATTR_PTR(static_feature, rmdir_subvol), + NULL +}; + +/* + * Features which only depend on a kernel version. + * These are listed in /sys/fs/btrfs/features along with + * btrfs_feature_attr_group + */ +static const struct attribute_group btrfs_static_feature_attr_group = { + .name = "features", + .attrs = btrfs_supported_static_feature_attrs, +}; + static ssize_t btrfs_show_u64(u64 *value_ptr, spinlock_t *lock, char *buf) { u64 val; @@ -901,8 +929,15 @@ int __init btrfs_init_sysfs(void) ret = sysfs_create_group(&btrfs_kset->kobj, &btrfs_feature_attr_group); if (ret) goto out2; + ret = sysfs_merge_group(&btrfs_kset->kobj, + &btrfs_static_feature_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 +948,8 @@ int __init btrfs_init_sysfs(void) void __cold btrfs_exit_sysfs(void) { + sysfs_unmerge_group(&btrfs_kset->kobj, + &btrfs_static_feature_attr_group); sysfs_remove_group(&btrfs_kset->kobj, &btrfs_feature_attr_group); kset_unregister(btrfs_kset); debugfs_remove_recursive(btrfs_debugfs_root_dentry); -- 2.14.3 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html