Re: Doubt in pagefault handler..!

[Andrew Morton <akpm@digeo.com>]

John Navil Joseph <cs99185@nitc.ac.in> wrote:
>
> 	1) add the current process to a wait queue 
> 	2) invoke schedule() from the page fault handler
> 	3) wake up the process after the transfer has been completed.

You probably don't need to do all that by hand - you should be calling
non-blocking functions in the network layer, and waking the faulting process
up on completion of network I/O (based on interrupt-time networking
callbacks).

Looking at the NFS and SMB client code may help.

> i tried to trace pagefault handler all the way down to where the acutal IO
> takes palce incase of the transfer of page from swap to memory..But i never
> saw schedule() anywhere. But i know that process sleeps on page I/O .. then
> how and where does this sleeping takes place.?

The faulting process will sleep in wait_on_page() or lock_page().  See
filemap_nopage(), around the page_not_uptodate label.

The filesystem's responsibility is to run unlock_page() against the page once
its contents have been filled in from the backing medium (disk, network,
etc).  it will typically do this from interrupt context.  The unlock_page()
will wake up the faulting process.

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