Implications of PG_locked and reference count in page structures....

[Michael Heinz]

I'm in the process of porting a driver to Linux. The author of the 
driver conveniently broke it into os-dependent and independent sections.

One of the things in the "OS" dependent section is a routine to lock a 
section of memory presumably to be used for DMA.

So, what I want to do is this: given a pointer to a previously 
kmalloc'ed block, and the length of that block, I want to (a) identify 
each page associated with the block and (b) lock each page. It appears 
that I can lock the page either by incrementing it's reference count, or 
by setting the PG_locked flag for the page.

Which method is preferred? Is there another method I should be using 
instead?