btrfs: publish per-super features in sysfs

This patch publishes information on which features are enabled in the
file system on a per-super basis. At this point, it only publishes
information on features supported by the file system implementation.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <clm@fb.com>

diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index 79be4a187af9e0478f882bda03ef6593125c9a72..832cf62151ffbf43998e98efe0457f6181a8e432 100644 (file)
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -28,29 +28,53 @@
 #include "transaction.h"
 #include "sysfs.h"
 
-static void btrfs_release_super_kobj(struct kobject *kobj);
-static struct kobj_type btrfs_ktype = {
-       .sysfs_ops      = &kobj_sysfs_ops,
-       .release        = btrfs_release_super_kobj,
-};
+static inline struct btrfs_fs_info *to_fs_info(struct kobject *kobj);
 
-static inline struct btrfs_fs_info *to_fs_info(struct kobject *kobj)
+static u64 get_features(struct btrfs_fs_info *fs_info,
+                       enum btrfs_feature_set set)
 {
-       if (kobj->ktype != &btrfs_ktype)
-               return NULL;
-       return container_of(kobj, struct btrfs_fs_info, super_kobj);
+       struct btrfs_super_block *disk_super = fs_info->super_copy;
+       if (set == FEAT_COMPAT)
+               return btrfs_super_compat_flags(disk_super);
+       else if (set == FEAT_COMPAT_RO)
+               return btrfs_super_compat_ro_flags(disk_super);
+       else
+               return btrfs_super_incompat_flags(disk_super);
 }
 
-static void btrfs_release_super_kobj(struct kobject *kobj)
+static ssize_t btrfs_feature_attr_show(struct kobject *kobj,
+                                      struct kobj_attribute *a, char *buf)
 {
+       int val = 0;
        struct btrfs_fs_info *fs_info = to_fs_info(kobj);
-       complete(&fs_info->kobj_unregister);
+       if (fs_info) {
+               struct btrfs_feature_attr *fa = to_btrfs_feature_attr(a);
+               u64 features = get_features(fs_info, fa->feature_set);
+               if (features & fa->feature_bit)
+                       val = 1;
+       }
+
+       return snprintf(buf, PAGE_SIZE, "%d\n", val);
 }
 
-static ssize_t btrfs_feature_attr_show(struct kobject *kobj,
-                                      struct kobj_attribute *a, char *buf)
+static umode_t btrfs_feature_visible(struct kobject *kobj,
+                                    struct attribute *attr, int unused)
 {
-       return snprintf(buf, PAGE_SIZE, "0\n");
+       struct btrfs_fs_info *fs_info = to_fs_info(kobj);
+       umode_t mode = attr->mode;
+
+       if (fs_info) {
+               struct btrfs_feature_attr *fa;
+               u64 features;
+
+               fa = attr_to_btrfs_feature_attr(attr);
+               features = get_features(fs_info, fa->feature_set);
+
+               if (!(features & fa->feature_bit))
+                       mode = 0;
+       }
+
+       return mode;
 }
 
 BTRFS_FEAT_ATTR_INCOMPAT(mixed_backref, MIXED_BACKREF);
@@ -78,11 +102,27 @@ static struct attribute *btrfs_supported_feature_attrs[] = {
 
 static const struct attribute_group btrfs_feature_attr_group = {
        .name = "features",
+       .is_visible = btrfs_feature_visible,
        .attrs = btrfs_supported_feature_attrs,
 };
 
-/* /sys/fs/btrfs/ entry */
-static struct kset *btrfs_kset;
+static void btrfs_release_super_kobj(struct kobject *kobj)
+{
+       struct btrfs_fs_info *fs_info = to_fs_info(kobj);
+       complete(&fs_info->kobj_unregister);
+}
+
+static struct kobj_type btrfs_ktype = {
+       .sysfs_ops      = &kobj_sysfs_ops,
+       .release        = btrfs_release_super_kobj,
+};
+
+static inline struct btrfs_fs_info *to_fs_info(struct kobject *kobj)
+{
+       if (kobj->ktype != &btrfs_ktype)
+               return NULL;
+       return container_of(kobj, struct btrfs_fs_info, super_kobj);
+}
 
 void btrfs_sysfs_remove_one(struct btrfs_fs_info *fs_info)
 {
@@ -91,13 +131,22 @@ void btrfs_sysfs_remove_one(struct btrfs_fs_info *fs_info)
        wait_for_completion(&fs_info->kobj_unregister);
 }
 
+/* /sys/fs/btrfs/ entry */
+static struct kset *btrfs_kset;
+
 int btrfs_sysfs_add_one(struct btrfs_fs_info *fs_info)
 {
        int error;
 
        init_completion(&fs_info->kobj_unregister);
+       fs_info->super_kobj.kset = btrfs_kset;
        error = kobject_init_and_add(&fs_info->super_kobj, &btrfs_ktype, NULL,
                                     "%pU", fs_info->fsid);
+
+       error = sysfs_create_group(&fs_info->super_kobj,
+                                  &btrfs_feature_attr_group);
+       if (error)
+               btrfs_sysfs_remove_one(fs_info);
        return error;
 }