Doing zero-copy stuff in drivers, or "is vm_fault_quick_hold_pages() enough" ?

[K. Macy]

>> Right above vm_page_hold():
>> /*
>>  * Keep page from being freed by the page daemon
>>  * much of the same effect as wiring, except much lower
>>  * overhead and should be used only for *very* temporary
>>  * holding ("wiring").
>>  */
>
> What's the definition of "very temporary holding" ? What's the
> behavioural difference?


Long enough to complete a DMA operation versus the lifetime of  an
executing program.