[PATCH] VFS: Permit filesystem to override root dentry on mount

[mirror_ubuntu-bionic-kernel.git] / fs / libfs.c

diff --git a/fs/libfs.c b/fs/libfs.c
index 63c020e6589e5c81e296f2eae3b9a2e5917aeee0..7d70efa46da962b56851d2647a16ff161b613f71 100644 (file)
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -7,6 +7,8 @@
 #include <linux/pagemap.h>
 #include <linux/mount.h>
 #include <linux/vfs.h>
+#include <linux/mutex.h>
+
 #include <asm/uaccess.h>
 
 int simple_getattr(struct vfsmount *mnt, struct dentry *dentry,
@@ -177,7 +179,7 @@ ssize_t generic_read_dir(struct file *filp, char __user *buf, size_t siz, loff_t
        return -EISDIR;
 }
 
-struct file_operations simple_dir_operations = {
+const struct file_operations simple_dir_operations = {
        .open           = dcache_dir_open,
        .release        = dcache_dir_close,
        .llseek         = dcache_dir_lseek,
@@ -194,9 +196,9 @@ struct inode_operations simple_dir_inode_operations = {
  * Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that
  * will never be mountable)
  */
-struct super_block *
-get_sb_pseudo(struct file_system_type *fs_type, char *name,
-       struct super_operations *ops, unsigned long magic)
+int get_sb_pseudo(struct file_system_type *fs_type, char *name,
+       struct super_operations *ops, unsigned long magic,
+       struct vfsmount *mnt)
 {
        struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL);
        static struct super_operations default_ops = {.statfs = simple_statfs};
@@ -205,7 +207,7 @@ get_sb_pseudo(struct file_system_type *fs_type, char *name,
        struct qstr d_name = {.name = name, .len = strlen(name)};
 
        if (IS_ERR(s))
-               return s;
+               return PTR_ERR(s);
 
        s->s_flags = MS_NOUSER;
        s->s_maxbytes = ~0ULL;
@@ -230,12 +232,12 @@ get_sb_pseudo(struct file_system_type *fs_type, char *name,
        d_instantiate(dentry, root);
        s->s_root = dentry;
        s->s_flags |= MS_ACTIVE;
-       return s;
+       return simple_set_mnt(mnt, s);
 
 Enomem:
        up_write(&s->s_umount);
        deactivate_super(s);
-       return ERR_PTR(-ENOMEM);
+       return -ENOMEM;
 }
 
 int simple_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
@@ -388,6 +390,7 @@ int simple_fill_super(struct super_block *s, int magic, struct tree_descr *files
        inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
        inode->i_op = &simple_dir_inode_operations;
        inode->i_fop = &simple_dir_operations;
+       inode->i_nlink = 2;
        root = d_alloc_root(inode);
        if (!root) {
                iput(inode);
@@ -529,7 +532,7 @@ struct simple_attr {
        char set_buf[24];
        void *data;
        const char *fmt;        /* format for read operation */
-       struct semaphore sem;   /* protects access to these buffers */
+       struct mutex mutex;     /* protects access to these buffers */
 };
 
 /* simple_attr_open is called by an actual attribute open file operation
@@ -548,7 +551,7 @@ int simple_attr_open(struct inode *inode, struct file *file,
        attr->set = set;
        attr->data = inode->u.generic_ip;
        attr->fmt = fmt;
-       init_MUTEX(&attr->sem);
+       mutex_init(&attr->mutex);
 
        file->private_data = attr;
 
@@ -574,7 +577,7 @@ ssize_t simple_attr_read(struct file *file, char __user *buf,
        if (!attr->get)
                return -EACCES;
 
-       down(&attr->sem);
+       mutex_lock(&attr->mutex);
        if (*ppos) /* continued read */
                size = strlen(attr->get_buf);
        else      /* first read */
@@ -583,7 +586,7 @@ ssize_t simple_attr_read(struct file *file, char __user *buf,
                                 (unsigned long long)attr->get(attr->data));
 
        ret = simple_read_from_buffer(buf, len, ppos, attr->get_buf, size);
-       up(&attr->sem);
+       mutex_unlock(&attr->mutex);
        return ret;
 }
 
@@ -601,7 +604,7 @@ ssize_t simple_attr_write(struct file *file, const char __user *buf,
        if (!attr->set)
                return -EACCES;
 
-       down(&attr->sem);
+       mutex_lock(&attr->mutex);
        ret = -EFAULT;
        size = min(sizeof(attr->set_buf) - 1, len);
        if (copy_from_user(attr->set_buf, buf, size))
@@ -612,7 +615,7 @@ ssize_t simple_attr_write(struct file *file, const char __user *buf,
        val = simple_strtol(attr->set_buf, NULL, 0);
        attr->set(attr->data, val);
 out:
-       up(&attr->sem);
+       mutex_unlock(&attr->mutex);
        return ret;
 }