[PATCH 2/3] z3fold: remove redundant locking

[Vitaly Wool]

The per-pool z3fold spinlock should generally be taken only when
a non-atomic pool variable is modified. There's no need to take it
to map/unmap an object.

Signed-off-by: Vitaly Wool <vitalyw...@gmail.com>
---
 mm/z3fold.c | 17 +++++------------
 1 file changed, 5 insertions(+), 12 deletions(-)

diff --git a/mm/z3fold.c b/mm/z3fold.c
index 5197d7b..10513b5 100644
--- a/mm/z3fold.c
+++ b/mm/z3fold.c
@@ -580,6 +580,7 @@ next:
                if ((test_bit(PAGE_HEADLESS, &page->private) && ret == 0) ||
                    (zhdr->first_chunks == 0 && zhdr->last_chunks == 0 &&
                     zhdr->middle_chunks == 0)) {
+                       spin_unlock(&pool->lock);
                        /*
                         * All buddies are now free, free the z3fold page and
                         * return success.
@@ -587,7 +588,6 @@ next:
                        clear_bit(PAGE_HEADLESS, &page->private);
                        free_z3fold_page(zhdr);
                        atomic64_dec(&pool->pages_nr);
-                       spin_unlock(&pool->lock);
                        return 0;
                }  else if (!test_bit(PAGE_HEADLESS, &page->private)) {
                        if (zhdr->first_chunks != 0 &&
@@ -629,7 +629,6 @@ static void *z3fold_map(struct z3fold_pool *pool, unsigned 
long handle)
        void *addr;
        enum buddy buddy;
 
-       spin_lock(&pool->lock);
        zhdr = handle_to_z3fold_header(handle);
        addr = zhdr;
        page = virt_to_page(zhdr);
@@ -656,7 +655,6 @@ static void *z3fold_map(struct z3fold_pool *pool, unsigned 
long handle)
                break;
        }
 out:
-       spin_unlock(&pool->lock);
        return addr;
 }
 
@@ -671,19 +669,14 @@ static void z3fold_unmap(struct z3fold_pool *pool, 
unsigned long handle)
        struct page *page;
        enum buddy buddy;
 
-       spin_lock(&pool->lock);
        zhdr = handle_to_z3fold_header(handle);
        page = virt_to_page(zhdr);
 
-       if (test_bit(PAGE_HEADLESS, &page->private)) {
-               spin_unlock(&pool->lock);
-               return;
+       if (!test_bit(PAGE_HEADLESS, &page->private)) {
+               buddy = handle_to_buddy(handle);
+               if (buddy == MIDDLE)
+                       clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
        }
-
-       buddy = handle_to_buddy(handle);
-       if (buddy == MIDDLE)
-               clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
-       spin_unlock(&pool->lock);
 }
 
 /**
-- 
2.4.2