On Mon, 30 Apr 2012, Dave Airlie wrote:
On Mon, Apr 30, 2012 at 6:53 PM, Dave Airlie <airlied@xxxxxxxxx> wrote:
Do you have pointers to that discussion (assuming it was on sime mailing
list)? The least I can do, while I am at it, is try to understand it and
see if I can incorporate some ideas from there in the rework of the patch.
Nope it was an offhand discussion on irc while we were talking about
some other ugly code.
Okay I think it was the code in coda,
if (coda_inode->i_mapping == &coda_inode->i_data)
coda_inode->i_mapping = host_inode->i_mapping;
/* only allow additional mmaps as long as userspace isn't changing
* the container file on us! */
else if (coda_inode->i_mapping != host_inode->i_mapping) {
spin_unlock(&cii->c_lock);
return -EBUSY;
}
We could use code like that to change the i_mapping, instead of failing.
Dave.
I have just cut (and sent to the list) a patch that, I believe, implements
this idea. I did it slightly differently from what coda fs does, but it's
the same concept. I set i_mapping in the open() instead of moving it
down to mmap(), because there are so many variants of mmap both in drm and
GPU-specific drivers, that it would get too messy.
I traced the code quite extensively with printks and it looks like it's
doing the right thing.
If the new patch seems right, then if and when we add render nodes, the
original dev_mapping patch that started this thread won't be needed any
more.
-- Ilija
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