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
---
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
--
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