confusing about the ramdisk(rd.c)--from 2.6

["rwen2012" <rwen2012@xxxxxxxxx>]

hi,all

 

   

   It seems that  block device drivers use the readpage() method of the address_space to get a page data from devices. And then the readpage() invorks the submit_bio() to execute a IO request, which results in the make_request_fn() does the real IO work.

 

    for ide-disk, the make_request_fn() is __make_request(), but for the ramdisk in rd.c, it is rd_make_request().

 

    What confuses me is that, the readpage() in the the rd.c does not do anything like submit_bio(), which does in ext2_readpage():

 

static int ramdisk_readpage(struct file *file, struct page *page)
{
 if (!PageUptodate(page))
  make_page_uptodate(page);
 unlock_page(page);
 return 0;
}

 

SO, when is the rd_make_request()(which is the function does the real work) to be invoked?

 

any reply would be appreciated.

 

R.wen

 

---

rwen2012

2007-06-06