mmap内核源码分析，基于内核版本3.10（总结）

通过（一）、（二）、（三）三部分算是比较混乱的把mmap内核代码给梳理了一遍，确实写得比较混乱，因此这里再做一个总结，总结一下mmap具体的实现。

1、系统调用陷入内核

1）用户态调用mmap函数，陷入内核

mmap(void *start, size_t length, int prot, int flags, int fd, off_t offset)

2）系统调用sys_mmap2函数被执行

sys_mmap2(unsigned long addr, size_t len,unsigned long prot, unsigned long flags,
			unsigned long fd, unsigned long pgoff)

3）sys_mmap2中调用do_mmap2

do_mmap2(unsigned long addr, size_t len, unsigned long prot, unsigned long flags,
			unsigned long fd, unsigned long off, int shift)

4）do_mmap2中调用sys_mmap_pgoff

sys_mmap_pgoff(unsigned long addr, unsigned long len, unsigned long prot, unsigned long flags,
			unsigned long fd, unsigned long pgoff);

5）sys_mmap_pgoff调用do_mmap_pgoff

 do_mmap_pgoff(struct file *file, unsigned long addr,
			unsigned long len, unsigned long prot