From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Mosberger Date: Fri, 24 May 2002 18:00:38 +0000 Subject: Re: [Linux-ia64] [PATCH] compilation fixes for i460 with 2.5.1[5-7] kernels Message-Id: List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org >>>>> On Fri, 24 May 2002 15:26:34 +1000, Peter Chubb said: Peter> Since 2.5.15, a few interfaces are no longer exported from Peter> filemap.c --- which means the code for getting and releasing Peter> locked pages in files .../agp/agpgart_be.c, .../drm/radeon.c, Peter> and .../drm/r128_cce.c has to be changed. Peter> Question: Is it *really* necessary to lock these pages? As Peter> they're grabbed from the freepage list, they're not backed by Peter> a file, so noone else will ever try to get the page. (Or Peter> have I misunderstood completely what's going on here?) So Peter> what's it locking against? I believe the locking is bogus. I'm no AGP expert, but my understanding is that what's going on there is that the agp code is allocating an scatter/gather table which is accessed by the GART ("AGP's DMA engine"). This table can be mapped into user level. I suspect the intent of the original code was to prevent swap-outs etc. on those pages. However, that's already taken care of by the vm-area which is used to map the memory into user level: it has the VM_RESERVED flag set (see drm_vm.h). BTW: I'm finally back to working on the 2.5 tree. I hope to have a (preliminary) 2.5.17 patch sometime today. --david