Commit f902bd3a authored by Misono Tomohiro's avatar Misono Tomohiro Committed by David Sterba
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btrfs: sysfs: Add entry which shows if rmdir can work on subvolumes 



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. fstests) can detect it.

Prior to this commit, all entries in /sys/fs/btrfs/features are feature
which depend 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 module. 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: default avatarTomohiro Misono <misono.tomohiro@jp.fujitsu.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 6c52157f

fs/btrfs/sysfs.c

+39 −0
Original line number Diff line number Diff line
@@ -210,12 +210,42 @@ 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 available 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 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 +931,15 @@ 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 out_remove_group;



	return 0;



out_remove_group:

	sysfs_remove_group(&btrfs_kset->kobj, &btrfs_feature_attr_group);

out2:

	debugfs_remove_recursive(btrfs_debugfs_root_dentry);

out1:
@@ -913,6 +950,8 @@ out1: 


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);

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