mtdchar: kill persistently held vfsmount

... and mtdchar_notifier along with it; just have ->drop_inode() that
will unconditionally get evict them instead of dances on mtd device
removal and use simple_pin_fs() instead of kern_mount()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 16 insertions, 37 deletions

diff --git a/drivers/mtd/mtdchar.c b/drivers/mtd/mtdchar.c
index c57ae92ebda4..28c585ffc8af 100644
--- a/drivers/mtd/mtdchar.c
+++ b/drivers/mtd/mtdchar.c
@@ -39,7 +39,6 @@
 #include <asm/uaccess.h>
 
 static DEFINE_MUTEX(mtd_mutex);
-static struct vfsmount *mtd_inode_mnt __read_mostly;
 
 /*
  * Data structure to hold the pointer to the mtd device as well
@@ -75,7 +74,9 @@ static loff_t mtdchar_lseek(struct file *file, loff_t offset, int orig)
         return -EINVAL;
 }
 
-
+static int count;
+static struct vfsmount *mnt;
+static struct file_system_type mtd_inodefs_type;
 
 static int mtdchar_open(struct inode *inode, struct file *file)
 {
@@ -92,6 +93,10 @@ static int mtdchar_open(struct inode *inode, struct file *file)
         if ((file->f_mode & FMODE_WRITE) && (minor & 1))
                 return -EACCES;
 
+        ret = simple_pin_fs(&mtd_inodefs_type, &mnt, &count);
+        if (ret)
+                return ret;
+
         mutex_lock(&mtd_mutex);
         mtd = get_mtd_device(NULL, devnum);
 
@@ -106,7 +111,7 @@ static int mtdchar_open(struct inode *inode, struct file *file)
                 goto out;
         }
 
-        mtd_ino = iget_locked(mtd_inode_mnt->mnt_sb, devnum);
+        mtd_ino = iget_locked(mnt->mnt_sb, devnum);
         if (!mtd_ino) {
                 put_mtd_device(mtd);
                 ret = -ENOMEM;
@@ -141,6 +146,7 @@ static int mtdchar_open(struct inode *inode, struct file *file)
 
 out:
         mutex_unlock(&mtd_mutex);
+        simple_release_fs(&mnt, &count);
         return ret;
 } /* mtdchar_open */
 
@@ -162,6 +168,7 @@ static int mtdchar_close(struct inode *inode, struct file *file)
         put_mtd_device(mtd);
         file->private_data = NULL;
         kfree(mfi);
+        simple_release_fs(&mnt, &count);
 
         return 0;
 } /* mtdchar_close */
@@ -1175,10 +1182,15 @@ static const struct file_operations mtd_fops = {
 #endif
 };
 
+static const struct super_operations mtd_ops = {
+        .drop_inode = generic_delete_inode,
+        .statfs = simple_statfs,
+};
+
 static struct dentry *mtd_inodefs_mount(struct file_system_type *fs_type,
                                 int flags, const char *dev_name, void *data)
 {
-        return mount_pseudo(fs_type, "mtd_inode:", NULL, NULL, MTD_INODE_FS_MAGIC);
+        return mount_pseudo(fs_type, "mtd_inode:", &mtd_ops, NULL, MTD_INODE_FS_MAGIC);
 }
 
 static struct file_system_type mtd_inodefs_type = {
@@ -1187,26 +1199,6 @@ static struct file_system_type mtd_inodefs_type = {
        .kill_sb = kill_anon_super,
 };
 
-static void mtdchar_notify_add(struct mtd_info *mtd)
-{
-}
-
-static void mtdchar_notify_remove(struct mtd_info *mtd)
-{
-        struct inode *mtd_ino = ilookup(mtd_inode_mnt->mnt_sb, mtd->index);
-
-        if (mtd_ino) {
-                /* Destroy the inode if it exists */
-                clear_nlink(mtd_ino);
-                iput(mtd_ino);
-        }
-}
-
-static struct mtd_notifier mtdchar_notifier = {
-        .add = mtdchar_notify_add,
-        .remove = mtdchar_notify_remove,
-};
-
 static int __init init_mtdchar(void)
 {
         int ret;
@@ -1224,19 +1216,8 @@ static int __init init_mtdchar(void)
                 pr_notice("Can't register mtd_inodefs filesystem: %d\n", ret);
                 goto err_unregister_chdev;
         }
-
-        mtd_inode_mnt = kern_mount(&mtd_inodefs_type);
-        if (IS_ERR(mtd_inode_mnt)) {
-                ret = PTR_ERR(mtd_inode_mnt);
-                pr_notice("Error mounting mtd_inodefs filesystem: %d\n", ret);
-                goto err_unregister_filesystem;
-        }
-        register_mtd_user(&mtdchar_notifier);
-
         return ret;
 
-err_unregister_filesystem:
-        unregister_filesystem(&mtd_inodefs_type);
 err_unregister_chdev:
         __unregister_chrdev(MTD_CHAR_MAJOR, 0, 1 << MINORBITS, "mtd");
         return ret;
@@ -1244,8 +1225,6 @@ err_unregister_chdev:
 
 static void __exit cleanup_mtdchar(void)
 {
-        unregister_mtd_user(&mtdchar_notifier);
-        kern_unmount(mtd_inode_mnt);
         unregister_filesystem(&mtd_inodefs_type);
         __unregister_chrdev(MTD_CHAR_MAJOR, 0, 1 << MINORBITS, "mtd");
 }