INIT_LIST_HEAD(&mnt->mnt_slave_list);
INIT_LIST_HEAD(&mnt->mnt_slave);
INIT_HLIST_NODE(&mnt->mnt_mp_list);
+ INIT_LIST_HEAD(&mnt->mnt_umounting);
init_fs_pin(&mnt->mnt_umount, drop_mountpoint);
}
return mnt;
}
/**
- * mnt_want_write_file - get write access to a file's mount
+ * mnt_want_write_file_path - get write access to a file's mount
* @file: the file who's mount on which to take a write
*
* This is like mnt_want_write, but it takes a file and can
* do some optimisations if the file is open for write already
+ *
+ * Called by the vfs for cases when we have an open file at hand, but will do an
+ * inode operation on it (important distinction for files opened on overlayfs,
+ * since the file operations will come from the real underlying file, while
+ * inode operations come from the overlay).
*/
-int mnt_want_write_file(struct file *file)
+int mnt_want_write_file_path(struct file *file)
{
int ret;
sb_end_write(file->f_path.mnt->mnt_sb);
return ret;
}
+
+static inline int may_write_real(struct file *file)
+{
+ struct dentry *dentry = file->f_path.dentry;
+ struct dentry *upperdentry;
+
+ /* Writable file? */
+ if (file->f_mode & FMODE_WRITER)
+ return 0;
+
+ /* Not overlayfs? */
+ if (likely(!(dentry->d_flags & DCACHE_OP_REAL)))
+ return 0;
+
+ /* File refers to upper, writable layer? */
+ upperdentry = d_real(dentry, NULL, 0, D_REAL_UPPER);
+ if (upperdentry && file_inode(file) == d_inode(upperdentry))
+ return 0;
+
+ /* Lower layer: can't write to real file, sorry... */
+ return -EPERM;
+}
+
+/**
+ * mnt_want_write_file - get write access to a file's mount
+ * @file: the file who's mount on which to take a write
+ *
+ * This is like mnt_want_write, but it takes a file and can
+ * do some optimisations if the file is open for write already
+ *
+ * Mostly called by filesystems from their ioctl operation before performing
+ * modification. On overlayfs this needs to check if the file is on a read-only
+ * lower layer and deny access in that case.
+ */
+int mnt_want_write_file(struct file *file)
+{
+ int ret;
+
+ ret = may_write_real(file);
+ if (!ret) {
+ sb_start_write(file_inode(file)->i_sb);
+ ret = __mnt_want_write_file(file);
+ if (ret)
+ sb_end_write(file_inode(file)->i_sb);
+ }
+ return ret;
+}
EXPORT_SYMBOL_GPL(mnt_want_write_file);
/**
__mnt_drop_write(file->f_path.mnt);
}
-void mnt_drop_write_file(struct file *file)
+void mnt_drop_write_file_path(struct file *file)
{
mnt_drop_write(file->f_path.mnt);
}
+
+void mnt_drop_write_file(struct file *file)
+{
+ __mnt_drop_write(file->f_path.mnt);
+ sb_end_write(file_inode(file)->i_sb);
+}
EXPORT_SYMBOL(mnt_drop_write_file);
static int mnt_make_readonly(struct mount *mnt)
void __init mnt_init(void)
{
- unsigned u;
int err;
mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct mount),
mount_hashtable = alloc_large_system_hash("Mount-cache",
sizeof(struct hlist_head),
mhash_entries, 19,
- 0,
+ HASH_ZERO,
&m_hash_shift, &m_hash_mask, 0, 0);
mountpoint_hashtable = alloc_large_system_hash("Mountpoint-cache",
sizeof(struct hlist_head),
mphash_entries, 19,
- 0,
+ HASH_ZERO,
&mp_hash_shift, &mp_hash_mask, 0, 0);
if (!mount_hashtable || !mountpoint_hashtable)
panic("Failed to allocate mount hash table\n");
- for (u = 0; u <= m_hash_mask; u++)
- INIT_HLIST_HEAD(&mount_hashtable[u]);
- for (u = 0; u <= mp_hash_mask; u++)
- INIT_HLIST_HEAD(&mountpoint_hashtable[u]);
-
kernfs_init();
err = sysfs_init();