[PATCH v2] f2fs: add symbolic link to kobject in sysfs

[Daeho Jeong]

From: Daeho Jeong <daehoje...@google.com>

Added a symbolic link to directory of sysfs. It will
create a symbolic link such as "mount_0" and "mount_1" to
each f2fs mount in the order of mounting filesystem. But
once one mount point was umounted, that sequential number
@x in "mount_@x" could be reused by later newly mounted
point. It will provide easy access to sysfs node even if
not knowing the specific device node name like sda19 and
dm-3.

Signed-off-by: Daeho Jeong <daehoje...@google.com>
---
 fs/f2fs/f2fs.h  |  4 ++++
 fs/f2fs/sysfs.c | 31 +++++++++++++++++++++++++++----
 2 files changed, 31 insertions(+), 4 deletions(-)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 4b28fd42fdbc..7d6c5f8ce16b 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1419,6 +1419,8 @@ struct decompress_io_ctx {
 #define MAX_COMPRESS_LOG_SIZE          8
 #define MAX_COMPRESS_WINDOW_SIZE       ((PAGE_SIZE) << MAX_COMPRESS_LOG_SIZE)
 
+#define MOUNT_NAME_SIZE                        20
+
 struct f2fs_sb_info {
        struct super_block *sb;                 /* pointer to VFS super block */
        struct proc_dir_entry *s_proc;          /* proc entry */
@@ -1599,6 +1601,8 @@ struct f2fs_sb_info {
        /* For sysfs suppport */
        struct kobject s_kobj;
        struct completion s_kobj_unregister;
+       int s_mount_id;
+       char s_mount_name[MOUNT_NAME_SIZE];
 
        /* For shrinker support */
        struct list_head s_list;
diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
index 2a140657fc4d..703d9f460d03 100644
--- a/fs/f2fs/sysfs.c
+++ b/fs/f2fs/sysfs.c
@@ -18,6 +18,7 @@
 #include <trace/events/f2fs.h>
 
 static struct proc_dir_entry *f2fs_proc_root;
+static struct ida f2fs_mount_ida;
 
 /* Sysfs support for f2fs */
 enum {
@@ -908,6 +909,9 @@ int __init f2fs_init_sysfs(void)
        } else {
                f2fs_proc_root = proc_mkdir("fs/f2fs", NULL);
        }
+
+       ida_init(&f2fs_mount_ida);
+
        return ret;
 }
 
@@ -917,6 +921,7 @@ void f2fs_exit_sysfs(void)
        kset_unregister(&f2fs_kset);
        remove_proc_entry("fs/f2fs", NULL);
        f2fs_proc_root = NULL;
+       ida_destroy(&f2fs_mount_ida);
 }
 
 int f2fs_register_sysfs(struct f2fs_sb_info *sbi)
@@ -928,12 +933,22 @@ int f2fs_register_sysfs(struct f2fs_sb_info *sbi)
        init_completion(&sbi->s_kobj_unregister);
        err = kobject_init_and_add(&sbi->s_kobj, &f2fs_sb_ktype, NULL,
                                "%s", sb->s_id);
-       if (err) {
-               kobject_put(&sbi->s_kobj);
-               wait_for_completion(&sbi->s_kobj_unregister);
-               return err;
+       if (err)
+               goto err1;
+
+       sbi->s_mount_id = ida_simple_get(&f2fs_mount_ida, 0, 0, GFP_KERNEL);
+       if (sbi->s_mount_id < 0) {
+               err = sbi->s_mount_id;
+               goto err1;
        }
 
+       snprintf(sbi->s_mount_name, MOUNT_NAME_SIZE, "mount_%d",
+                       sbi->s_mount_id);
+       err = sysfs_create_link(&f2fs_kset.kobj, &sbi->s_kobj,
+                       sbi->s_mount_name);
+       if (err)
+               goto err2;
+
        if (f2fs_proc_root)
                sbi->s_proc = proc_mkdir(sb->s_id, f2fs_proc_root);
 
@@ -948,6 +963,12 @@ int f2fs_register_sysfs(struct f2fs_sb_info *sbi)
                                victim_bits_seq_show, sb);
        }
        return 0;
+err2:
+       ida_simple_remove(&f2fs_mount_ida, sbi->s_mount_id);
+err1:
+       kobject_put(&sbi->s_kobj);
+       wait_for_completion(&sbi->s_kobj_unregister);
+       return err;
 }
 
 void f2fs_unregister_sysfs(struct f2fs_sb_info *sbi)
@@ -959,6 +980,8 @@ void f2fs_unregister_sysfs(struct f2fs_sb_info *sbi)
                remove_proc_entry("victim_bits", sbi->s_proc);
                remove_proc_entry(sbi->sb->s_id, f2fs_proc_root);
        }
+       sysfs_remove_link(&f2fs_kset.kobj, sbi->s_mount_name);
+       ida_simple_remove(&f2fs_mount_ida, sbi->s_mount_id);
        kobject_del(&sbi->s_kobj);
        kobject_put(&sbi->s_kobj);
 }
-- 
2.27.0.383.g050319c2ae-goog