本文主要是介绍微视linux 文件系统之打开文件返回只读，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
struct file *do_last(struct nameidata *nd, struct path *path,int open_flag, int acc_mode,int mode, const char *pathname)
{if (!(open_flag & O_CREAT)) {error = do_lookup(nd, &nd->last, path);if (error)goto exit;error = -ENOENT;//不让以创建方式打开，那么如果找不到则返回if (!path->dentry->d_inode)goto exit_dput;goto ok;}/* Negative dentry, just create the file */if (!path->dentry->d_inode) {error = mnt_want_write(nd->path.mnt);=>int mnt_want_write(struct vfsmount *mnt){if (__mnt_is_readonly(mnt)) {dec_mnt_writers(mnt);ret = -EROFS;//打开失败，由于是只读模式goto out;}out:return ret;}if (error)goto exit_mutex_unlock;}
ok:filp = finish_open(nd, open_flag, acc_mode);=>struct file *finish_open(struct nameidata *nd,int open_flag, int acc_mode){error = may_open(&nd->path, acc_mode, open_flag);=>int may_open(struct path *path, int acc_mode, int flag){error = inode_permission(inode, acc_mode);=>int inode_permission(struct inode *inode, int mask){if (mask & MAY_WRITE) {//写模式下权限的判断umode_t mode = inode->i_mode;/** Nobody gets write access to a read-only fs.*/if (IS_RDONLY(inode) &&(S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))return -EROFS;//只读/** Nobody gets write access to an immutable file.*/if (IS_IMMUTABLE(inode))return -EACCES;}}if (error)return error;}if (error) {if (will_truncate)mnt_drop_write(nd->path.mnt);goto exit;}}return filp;exit_mutex_unlock:mutex_unlock(&dir->d_inode->i_mutex);
exit_dput:path_put_conditional(path, nd);
exit:if (!IS_ERR(nd->intent.open.file))release_open_intent(nd);path_put(&nd->path);return ERR_PTR(error);
}
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