mm/hmm.c: remove superfluous RCU protection around radix tree lookup
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 superfluous 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. Link: http://lkml.kernel.org/r/20180314194515.1661824-4-tj@kernel.org Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: Jérôme Glisse <jglisse@redhat.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Benjamin LaHaise <bcrl@kvack.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Kent Overstreet <kent.overstreet@gmail.com> Cc: Matthew Wilcox <willy@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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mm/hmm.c
12
mm/hmm.c
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@ -1024,13 +1024,6 @@ static void hmm_devmem_release(struct device *dev, void *data)
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hmm_devmem_radix_release(resource);
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hmm_devmem_radix_release(resource);
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}
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}
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static struct hmm_devmem *hmm_devmem_find(resource_size_t phys)
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{
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WARN_ON_ONCE(!rcu_read_lock_held());
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return radix_tree_lookup(&hmm_devmem_radix, phys >> PA_SECTION_SHIFT);
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}
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static int hmm_devmem_pages_create(struct hmm_devmem *devmem)
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static int hmm_devmem_pages_create(struct hmm_devmem *devmem)
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{
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{
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resource_size_t key, align_start, align_size, align_end;
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resource_size_t key, align_start, align_size, align_end;
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@ -1071,9 +1064,8 @@ static int hmm_devmem_pages_create(struct hmm_devmem *devmem)
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for (key = align_start; key <= align_end; key += PA_SECTION_SIZE) {
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for (key = align_start; key <= align_end; key += PA_SECTION_SIZE) {
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struct hmm_devmem *dup;
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struct hmm_devmem *dup;
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rcu_read_lock();
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dup = radix_tree_lookup(&hmm_devmem_radix,
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dup = hmm_devmem_find(key);
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key >> PA_SECTION_SHIFT);
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rcu_read_unlock();
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if (dup) {
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if (dup) {
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dev_err(device, "%s: collides with mapping for %s\n",
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dev_err(device, "%s: collides with mapping for %s\n",
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__func__, dev_name(dup->device));
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__func__, dev_name(dup->device));
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