From: "Russell Johnson" <rjohnson@rtlogic.com>
To: <linux-kernel@vger.kernel.org>
Subject: bigphysarea mmap and direct_io
Date: Fri, 6 Oct 2006 07:18:39 -0600 [thread overview]
Message-ID: <003101c6e949$f018cf40$f500030a@rtlogic.com> (raw)
My driver is allocating memory via bigphysarea and my application mmap's the
area for performance reasons. With linux kernels 2.6.14 and prior on i386
platforms, I have been able to issue disk reads using direct_io to fill this
bigphysarea memory and prevent multiple copies of the data. The file system
code for direct I/O disk reads checks for VM_IO and will not allow direct io
in that case. So to do this I had my driver clear the VM_IO flag after
calling remap_pfn_range.
With kernel 2.6.16 and newer, remap_pfn_range sets a new flag VM_PFNMAP
which direct_io also checks. If my driver clears VM_PFNMAP then the kernel
will oops upon an munmap call because it will attempt to free the pages.
I'm looking for the proper way to do what I want which is to allow the
application to mmap and do direct io disk access to the bigphysarea memory.
I've unsuccessfully tried writing a nopage handler and I still get an oops
upon munmap. Can someone point me in the right direction?
Please cc me as I'm not on this list. Thanks!
rjohnson@rtlogic.com
Russell Johnson
RT Logic!
reply other threads:[~2006-10-06 13:18 UTC|newest]
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