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Subject[PATCH v5 2/3] z3fold: remove redundant locking
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 <vitalywool@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
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