On Mon, Mar 26, 2018 at 07:54:31AM -0700, Tejun Heo wrote: > Hello, Andrew. > > Do you mind picking up the following patch? I can't find a good tree > to route this through. The raw patch can be found at > > https://marc.info/?l=linux-mm&m=152105674112496&q=raw > > Thank you very much. I am fine with which ever route there is low probability of conflict when merging HMM through different tree. > > On Wed, Mar 14, 2018 at 12:45:11PM -0700, Tejun Heo wrote: > > hmm_devmem_find() requires rcu_read_lock_held() but there's nothing > > which actually uses the RCU protection. The only caller is > > hmm_devmem_pages_create() which already grabs the mutex and does > > superflous rcu_read_lock/unlock() around the function. > > > > This doesn't add anything and just adds to confusion. Remove the RCU > > protection and open-code the radix tree lookup. If this needs to > > become more sophisticated in the future, let's add them back when > > necessary. > > > > Signed-off-by: Tejun Heo <tj@xxxxxxxxxx> > > Reviewed-by: Jérôme Glisse <jglisse@xxxxxxxxxx> > > Cc: linux-mm@xxxxxxxxx > > Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> > > --- > > Hello, > > > > Jérôme, how do you want to route this patch? If you prefer, I can > > route it together with other patches. > > > > Thanks. > > > > mm/hmm.c | 12 ++---------- > > 1 file changed, 2 insertions(+), 10 deletions(-) > > > > diff --git a/mm/hmm.c b/mm/hmm.c > > index 320545b98..d4627c5 100644 > > --- a/mm/hmm.c > > +++ b/mm/hmm.c > > @@ -845,13 +845,6 @@ static void hmm_devmem_release(struct device *dev, void *data) > > hmm_devmem_radix_release(resource); > > } > > > > -static struct hmm_devmem *hmm_devmem_find(resource_size_t phys) > > -{ > > - WARN_ON_ONCE(!rcu_read_lock_held()); > > - > > - return radix_tree_lookup(&hmm_devmem_radix, phys >> PA_SECTION_SHIFT); > > -} > > - > > static int hmm_devmem_pages_create(struct hmm_devmem *devmem) > > { > > resource_size_t key, align_start, align_size, align_end; > > @@ -892,9 +885,8 @@ static int hmm_devmem_pages_create(struct hmm_devmem *devmem) > > for (key = align_start; key <= align_end; key += PA_SECTION_SIZE) { > > struct hmm_devmem *dup; > > > > - rcu_read_lock(); > > - dup = hmm_devmem_find(key); > > - rcu_read_unlock(); > > + dup = radix_tree_lookup(&hmm_devmem_radix, > > + key >> PA_SECTION_SHIFT); > > if (dup) { > > dev_err(device, "%s: collides with mapping for %s\n", > > __func__, dev_name(dup->device)); > > -- > > 2.9.5 > > > > -- > tejun
