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| author |   Tejun Heo <tj@kernel.org> | 2018-04-10 16:29:09 -0700 |
|---|---|---|
| committer |   Linus Torvalds <torvalds@linux-foundation.org> | 2018-04-11 10:28:31 -0700 |
| commit | 18be460eeb2cd3f4bfb6498b10ce5b800f9a20ea (patch) | |
| tree | 2e1462c470d5f7edb26dfb6cae4e8d10a34cfeb9 /mm | |
| parent | mm/hmm: use device driver encoding for HMM pfn (diff) | |
| download | linux-dev-18be460eeb2cd3f4bfb6498b10ce5b800f9a20ea.tar.xz linux-dev-18be460eeb2cd3f4bfb6498b10ce5b800f9a20ea.zip | |
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>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/hmm.c | 12 |
1 files changed, 2 insertions, 10 deletions
@@ -1024,13 +1024,6 @@ 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; @@ -1071,9 +1064,8 @@ 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)); |