nilfs2: add /sys/fs/nilfs2/<device>/mounted_snapshots/<snapshot> group

This patch adds creation of <snapshot> group for every mounted
snapshot in /sys/fs/nilfs2/<device>/mounted_snapshots group.

The group contains details about mounted snapshot:
(1) inodes_count - show number of inodes for snapshot.
(2) blocks_count - show number of blocks for snapshot.

Signed-off-by: Vyacheslav Dubeyko <Vyacheslav.Dubeyko@hgst.com>
Cc: Vyacheslav Dubeyko <slava@dubeyko.com>
Cc: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Cc: Michael L. Semon <mlsemon35@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 144 insertions, 0 deletions

diff --git a/fs/nilfs2/sysfs.c b/fs/nilfs2/sysfs.c
index fc0c961d486a..0f6148c8121a 100644
--- a/fs/nilfs2/sysfs.c
+++ b/fs/nilfs2/sysfs.c
@@ -112,6 +112,124 @@ void nilfs_sysfs_delete_##name##_group(struct the_nilfs *nilfs) \
 }
 
 /************************************************************************
+ *                        NILFS snapshot attrs                          *
+ ************************************************************************/
+
+static ssize_t
+nilfs_snapshot_inodes_count_show(struct nilfs_snapshot_attr *attr,
+                                 struct nilfs_root *root, char *buf)
+{
+        return snprintf(buf, PAGE_SIZE, "%llu\n",
+                        (unsigned long long)atomic64_read(&root->inodes_count));
+}
+
+static ssize_t
+nilfs_snapshot_blocks_count_show(struct nilfs_snapshot_attr *attr,
+                                 struct nilfs_root *root, char *buf)
+{
+        return snprintf(buf, PAGE_SIZE, "%llu\n",
+                        (unsigned long long)atomic64_read(&root->blocks_count));
+}
+
+static const char snapshot_readme_str[] =
+        "The group contains details about mounted snapshot.\n\n"
+        "(1) inodes_count\n\tshow number of inodes for snapshot.\n\n"
+        "(2) blocks_count\n\tshow number of blocks for snapshot.\n\n";
+
+static ssize_t
+nilfs_snapshot_README_show(struct nilfs_snapshot_attr *attr,
+                            struct nilfs_root *root, char *buf)
+{
+        return snprintf(buf, PAGE_SIZE, snapshot_readme_str);
+}
+
+NILFS_SNAPSHOT_RO_ATTR(inodes_count);
+NILFS_SNAPSHOT_RO_ATTR(blocks_count);
+NILFS_SNAPSHOT_RO_ATTR(README);
+
+static struct attribute *nilfs_snapshot_attrs[] = {
+        NILFS_SNAPSHOT_ATTR_LIST(inodes_count),
+        NILFS_SNAPSHOT_ATTR_LIST(blocks_count),
+        NILFS_SNAPSHOT_ATTR_LIST(README),
+        NULL,
+};
+
+static ssize_t nilfs_snapshot_attr_show(struct kobject *kobj,
+                                        struct attribute *attr, char *buf)
+{
+        struct nilfs_root *root =
+                        container_of(kobj, struct nilfs_root, snapshot_kobj);
+        struct nilfs_snapshot_attr *a =
+                        container_of(attr, struct nilfs_snapshot_attr, attr);
+
+        return a->show ? a->show(a, root, buf) : 0;
+}
+
+static ssize_t nilfs_snapshot_attr_store(struct kobject *kobj,
+                                         struct attribute *attr,
+                                         const char *buf, size_t len)
+{
+        struct nilfs_root *root =
+                        container_of(kobj, struct nilfs_root, snapshot_kobj);
+        struct nilfs_snapshot_attr *a =
+                        container_of(attr, struct nilfs_snapshot_attr, attr);
+
+        return a->store ? a->store(a, root, buf, len) : 0;
+}
+
+static void nilfs_snapshot_attr_release(struct kobject *kobj)
+{
+        struct nilfs_root *root = container_of(kobj, struct nilfs_root,
+                                                snapshot_kobj);
+        complete(&root->snapshot_kobj_unregister);
+}
+
+static const struct sysfs_ops nilfs_snapshot_attr_ops = {
+        .show   = nilfs_snapshot_attr_show,
+        .store  = nilfs_snapshot_attr_store,
+};
+
+static struct kobj_type nilfs_snapshot_ktype = {
+        .default_attrs  = nilfs_snapshot_attrs,
+        .sysfs_ops      = &nilfs_snapshot_attr_ops,
+        .release        = nilfs_snapshot_attr_release,
+};
+
+int nilfs_sysfs_create_snapshot_group(struct nilfs_root *root)
+{
+        struct the_nilfs *nilfs;
+        struct kobject *parent;
+        int err;
+
+        nilfs = root->nilfs;
+        parent = &nilfs->ns_dev_subgroups->sg_mounted_snapshots_kobj;
+        root->snapshot_kobj.kset = nilfs_kset;
+        init_completion(&root->snapshot_kobj_unregister);
+
+        if (root->cno == NILFS_CPTREE_CURRENT_CNO) {
+                err = kobject_init_and_add(&root->snapshot_kobj,
+                                            &nilfs_snapshot_ktype,
+                                            &nilfs->ns_dev_kobj,
+                                            "current_checkpoint");
+        } else {
+                err = kobject_init_and_add(&root->snapshot_kobj,
+                                            &nilfs_snapshot_ktype,
+                                            parent,
+                                            "%llu", root->cno);
+        }
+
+        if (err)
+                return err;
+
+        return 0;
+}
+
+void nilfs_sysfs_delete_snapshot_group(struct nilfs_root *root)
+{
+        kobject_del(&root->snapshot_kobj);
+}
+
+/************************************************************************
  *                    NILFS mounted snapshots attrs                     *
  ************************************************************************/
 
diff --git a/fs/nilfs2/sysfs.h b/fs/nilfs2/sysfs.h
index 4e84e230e9dd..677e3a1a8370 100644
--- a/fs/nilfs2/sysfs.h
+++ b/fs/nilfs2/sysfs.h
@@ -86,6 +86,17 @@ NILFS_DEV_ATTR_STRUCT(checkpoints);
 NILFS_DEV_ATTR_STRUCT(superblock);
 NILFS_DEV_ATTR_STRUCT(segctor);
 
+#define NILFS_CP_ATTR_STRUCT(name) \
+struct nilfs_##name##_attr { \
+        struct attribute attr; \
+        ssize_t (*show)(struct nilfs_##name##_attr *, struct nilfs_root *, \
+                        char *); \
+        ssize_t (*store)(struct nilfs_##name##_attr *, struct nilfs_root *, \
+                         const char *, size_t); \
+};
+
+NILFS_CP_ATTR_STRUCT(snapshot);
+
 #define NILFS_ATTR(type, name, mode, show, store) \
         static struct nilfs_##type##_attr nilfs_##type##_attr_##name = \
                 __ATTR(name, mode, show, store)
@@ -126,6 +137,13 @@ NILFS_DEV_ATTR_STRUCT(segctor);
 #define NILFS_CHECKPOINTS_RW_ATTR(name) \
         NILFS_RW_ATTR(checkpoints, name)
 
+#define NILFS_SNAPSHOT_INFO_ATTR(name) \
+        NILFS_INFO_ATTR(snapshot, name)
+#define NILFS_SNAPSHOT_RO_ATTR(name) \
+        NILFS_RO_ATTR(snapshot, name)
+#define NILFS_SNAPSHOT_RW_ATTR(name) \
+        NILFS_RW_ATTR(snapshot, name)
+
 #define NILFS_SUPERBLOCK_RO_ATTR(name) \
         NILFS_RO_ATTR(superblock, name)
 #define NILFS_SUPERBLOCK_RW_ATTR(name) \
@@ -148,6 +166,8 @@ NILFS_DEV_ATTR_STRUCT(segctor);
         (&nilfs_mounted_snapshots_attr_##name.attr)
 #define NILFS_CHECKPOINTS_ATTR_LIST(name) \
         (&nilfs_checkpoints_attr_##name.attr)
+#define NILFS_SNAPSHOT_ATTR_LIST(name) \
+        (&nilfs_snapshot_attr_##name.attr)
 #define NILFS_SUPERBLOCK_ATTR_LIST(name) \
         (&nilfs_superblock_attr_##name.attr)
 #define NILFS_SEGCTOR_ATTR_LIST(name) \
diff --git a/fs/nilfs2/the_nilfs.h b/fs/nilfs2/the_nilfs.h
index 7fe822307f98..d01ead1bea9a 100644
--- a/fs/nilfs2/the_nilfs.h
+++ b/fs/nilfs2/the_nilfs.h
@@ -243,6 +243,8 @@ THE_NILFS_FNS(SB_DIRTY, sb_dirty)
  * @ifile: inode file
  * @inodes_count: number of inodes
  * @blocks_count: number of blocks
+ * @snapshot_kobj: /sys/fs/<nilfs>/<device>/mounted_snapshots/<snapshot>
+ * @snapshot_kobj_unregister: completion state for kernel object
  */
 struct nilfs_root {
         __u64 cno;
@@ -254,6 +256,10 @@ struct nilfs_root {
 
         atomic64_t inodes_count;
         atomic64_t blocks_count;
+
+        /* /sys/fs/<nilfs>/<device>/mounted_snapshots/<snapshot> */
+        struct kobject snapshot_kobj;
+        struct completion snapshot_kobj_unregister;
 };
 
 /* Special checkpoint number */