Erofs over fscache need CONFIG_CACHEFILES_ONDEMAND in cachefiles
module. We cannot know whether it is supported from userspace, so
we export this feature to user by sysfs interface.
[Before]
$ cat /sys/fs/cachefiles/features/cachefiles_ondemand
cat: /sys/fs/cachefiles/features/cachefiles_ondemand: No such file or directory
[After]
$ cat /sys/fs/cachefiles/features/cachefiles_ondemand
supported
Signed-off-by: Hongbo Li <lihongb...@huawei.com>
---
fs/cachefiles/Makefile | 3 +-
fs/cachefiles/internal.h | 7 +++
fs/cachefiles/main.c | 7 +++
fs/cachefiles/sysfs.c | 101 +++++++++++++++++++++++++++++++++++++++
4 files changed, 117 insertions(+), 1 deletion(-)
create mode 100644 fs/cachefiles/sysfs.c
diff --git a/fs/cachefiles/Makefile b/fs/cachefiles/Makefile
index c37a7a9af10b..e5d9dd27f94f 100644
--- a/fs/cachefiles/Makefile
+++ b/fs/cachefiles/Makefile
@@ -13,7 +13,8 @@ cachefiles-y := \
namei.o \
security.o \
volume.o \
- xattr.o
+ xattr.o \
+ sysfs.o
cachefiles-$(CONFIG_CACHEFILES_ERROR_INJECTION) += error_inject.o
cachefiles-$(CONFIG_CACHEFILES_ONDEMAND) += ondemand.o
diff --git a/fs/cachefiles/internal.h b/fs/cachefiles/internal.h
index 6845a90cdfcc..4926684b3044 100644
--- a/fs/cachefiles/internal.h
+++ b/fs/cachefiles/internal.h
@@ -419,6 +419,13 @@ extern void cachefiles_prepare_to_write(struct
fscache_cookie *cookie);
extern bool cachefiles_set_volume_xattr(struct cachefiles_volume *volume);
extern int cachefiles_check_volume_xattr(struct cachefiles_volume *volume);
+/*
+ * sysfs.c
+ */
+
+int __init cachefiles_init_sysfs(void);
+void cachefiles_exit_sysfs(void);
+
/*
* Error handling
*/
diff --git a/fs/cachefiles/main.c b/fs/cachefiles/main.c
index 3f369c6f816d..0dcad6bb4b1f 100644
--- a/fs/cachefiles/main.c
+++ b/fs/cachefiles/main.c
@@ -64,9 +64,15 @@ static int __init cachefiles_init(void)
goto error_object_jar;
}
+ ret = cachefiles_init_sysfs();
+ if (ret)
+ goto sysfs_err;
+
pr_info("Loaded\n");
return 0;
+sysfs_err:
+ kmem_cache_destroy(cachefiles_object_jar);
error_object_jar:
misc_deregister(&cachefiles_dev);
error_dev:
@@ -85,6 +91,7 @@ static void __exit cachefiles_exit(void)
{
pr_info("Unloading\n");
+ cachefiles_exit_sysfs();
kmem_cache_destroy(cachefiles_object_jar);
misc_deregister(&cachefiles_dev);
cachefiles_unregister_error_injection();
diff --git a/fs/cachefiles/sysfs.c b/fs/cachefiles/sysfs.c
new file mode 100644
index 000000000000..adfb260df59c
--- /dev/null
+++ b/fs/cachefiles/sysfs.c
@@ -0,0 +1,101 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+#include <linux/sysfs.h>
+#include <linux/kobject.h>
+
+#include "internal.h"
+
+enum {
+ attr_feature,
+};
+
+struct cachefiles_attr {
+ struct attribute attr;
+ short attr_id;
+};
+
+#define CACHEFILES_ATTR(_name, _mode, _id) \
+static struct cachefiles_attr cachefiles_attr_##_name = { \
+ .attr = {.name = __stringify(_name), .mode = _mode }, \
+ .attr_id = attr_##_id, \
+}
+
+#define CACHEFILES_ATTR_FEATURE(_name) CACHEFILES_ATTR(_name, 0444, feature)
+
+#define ATTR_LIST(name) (&cachefiles_attr_##name.attr)
+
+/* supported features of cachefiles */
+#if IS_ENABLED(CONFIG_CACHEFILES_ONDEMAND)
+CACHEFILES_ATTR_FEATURE(cachefiles_ondemand);
+#endif
+
+static struct attribute *cachefiles_feat_attrs[] = {
+#if IS_ENABLED(CONFIG_CACHEFILES_ONDEMAND)
+ ATTR_LIST(cachefiles_ondemand),
+ NULL,
+#endif
+};
+
+ATTRIBUTE_GROUPS(cachefiles_feat);
+
+static ssize_t cachefiles_attr_show(struct kobject *kobj,
+ struct attribute *attr, char *buf)
+{
+ struct cachefiles_attr *a = container_of(attr, struct cachefiles_attr,
attr);
+
+ switch (a->attr_id) {
+ case attr_feature:
+ return sysfs_emit(buf, "supported\n");
+ }
+
+ return 0;
+};
+
+static const struct sysfs_ops cachefiles_attr_ops = {
+ .show = cachefiles_attr_show,
+};
+
+static const struct kobj_type cachefiles_ktype = {
+ .sysfs_ops = &cachefiles_attr_ops,
+};
+
+static struct kset cachefiles_root = {
+ .kobj = {.ktype = &cachefiles_ktype},
+};
+
+static const struct kobj_type cachefiles_feat_ktype = {
+ .default_groups = cachefiles_feat_groups,
+ .sysfs_ops = &cachefiles_attr_ops,
+};
+
+static struct kobject cachefiles_feat = {
+ .kset = &cachefiles_root,
+};
+
+int __init cachefiles_init_sysfs(void)
+{
+ int ret;
+
+ kobject_set_name(&cachefiles_root.kobj, "cachefiles");
+ cachefiles_root.kobj.parent = fs_kobj;
+ ret = kset_register(&cachefiles_root);
+ if (ret)
+ goto root_err;
+
+ ret = kobject_init_and_add(&cachefiles_feat, &cachefiles_feat_ktype,
+ NULL, "features");
+ if (ret)
+ goto feat_err;
+ return ret;
+
+feat_err:
+ kobject_put(&cachefiles_feat);
+ kset_unregister(&cachefiles_root);
+root_err:
+ return ret;
+}
+
+void cachefiles_exit_sysfs(void)
+{
+ kobject_put(&cachefiles_feat);
+ kset_unregister(&cachefiles_root);
+}
--
2.34.1
