This patch use swap method to implement bh_lru_install,
it works like this:
swap new and [0] first, update old=[0],
then compare old and [1],
if old != new_bh && old != NULL, swap old and [1],
then start the next compare,
otherwise stop the compare.
Signed-off-by: yalin wang <yalin.wang2010@xxxxxxxxx>
---
fs/buffer.c | 33 ++++++++++++---------------------
1 file changed, 12 insertions(+), 21 deletions(-)
diff --git a/fs/buffer.c b/fs/buffer.c
index 82283ab..d6769f1 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -1287,40 +1287,31 @@ static inline void check_irqs_on(void)
*/
static void bh_lru_install(struct buffer_head *bh)
{
- struct buffer_head *evictee = NULL;
+ struct buffer_head *old = NULL;
check_irqs_on();
bh_lru_lock();
if (__this_cpu_read(bh_lrus.bhs[0]) != bh) {
- struct buffer_head *bhs[BH_LRU_SIZE];
- int in;
+ struct buffer_head *temp;
int out = 0;
+ old = __this_cpu_read(bh_lrus.bhs[0]);
get_bh(bh);
- bhs[out++] = bh;
- for (in = 0; in < BH_LRU_SIZE; in++) {
- struct buffer_head *bh2 =
- __this_cpu_read(bh_lrus.bhs[in]);
-
- if (bh2 == bh) {
- __brelse(bh2);
+ __this_cpu_write(bh_lrus.bhs[out++], bh);
+ for (; out < BH_LRU_SIZE; out++) {
+ if (old == bh || old == NULL) {
+ break;
} else {
- if (out >= BH_LRU_SIZE) {
- BUG_ON(evictee != NULL);
- evictee = bh2;
- } else {
- bhs[out++] = bh2;
- }
+ temp = __this_cpu_read(bh_lrus.bhs[out]);
+ __this_cpu_write(bh_lrus.bhs[out], old);
+ old = temp;
}
}
- while (out < BH_LRU_SIZE)
- bhs[out++] = NULL;
- memcpy(this_cpu_ptr(&bh_lrus.bhs), bhs, sizeof(bhs));
}
bh_lru_unlock();
- if (evictee)
- __brelse(evictee);
+ if (old)
+ __brelse(old);
}
/*
--
1.9.1
--
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