[Libguestfs] [PATCH v4 06/24] nbd/client: Simplify cookie vs. index computation
Our code relies on a sentinel cookie value of zero for deciding when a
packet has been handled, as well as relying on array indices between 0
and MAX_NBD_REQUESTS-1 for dereferencing purposes. As long as we can
symmetrically convert between two forms, there is no reason to go with
the odd choice of using XOR with a random pointer, when we can instead
simplify the mappings with a mere offset of 1.
Signed-off-by: Eric Blake <eblake(a)redhat.com>
---
v4: new patch
---
block/nbd.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)
diff --git a/block/nbd.c b/block/nbd.c
index be3c46c6fee..5322e66166c 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -50,8 +50,8 @@
#define EN_OPTSTR ":exportname="
#define MAX_NBD_REQUESTS 16
-#define COOKIE_TO_INDEX(bs, cookie) ((cookie) ^ (uint64_t)(intptr_t)(bs))
-#define INDEX_TO_COOKIE(bs, index) ((index) ^ (uint64_t)(intptr_t)(bs))
+#define COOKIE_TO_INDEX(cookie) ((cookie) - 1)
+#define INDEX_TO_COOKIE(index) ((index) + 1)
typedef struct {
Coroutine *coroutine;
@@ -420,7 +420,7 @@ static void coroutine_fn GRAPH_RDLOCK
nbd_reconnect_attempt(BDRVNBDState *s)
static coroutine_fn int nbd_receive_replies(BDRVNBDState *s, uint64_t cookie)
{
int ret;
- uint64_t ind = COOKIE_TO_INDEX(s, cookie), ind2;
+ uint64_t ind = COOKIE_TO_INDEX(cookie), ind2;
QEMU_LOCK_GUARD(&s->receive_mutex);
while (true) {
@@ -435,7 +435,7 @@ static coroutine_fn int nbd_receive_replies(BDRVNBDState *s, uint64_t
cookie)
* woken by whoever set s->reply.cookie (or never wait in this
* yield). So, we should not wake it here.
*/
- ind2 = COOKIE_TO_INDEX(s, s->reply.cookie);
+ ind2 = COOKIE_TO_INDEX(s->reply.cookie);
assert(!s->requests[ind2].receiving);
s->requests[ind].receiving = true;
@@ -468,7 +468,7 @@ static coroutine_fn int nbd_receive_replies(BDRVNBDState *s, uint64_t
cookie)
nbd_channel_error(s, -EINVAL);
return -EINVAL;
}
- ind2 = COOKIE_TO_INDEX(s, s->reply.cookie);
+ ind2 = COOKIE_TO_INDEX(s->reply.cookie);
if (ind2 >= MAX_NBD_REQUESTS || !s->requests[ind2].coroutine) {
nbd_channel_error(s, -EINVAL);
return -EINVAL;
@@ -519,7 +519,7 @@ nbd_co_send_request(BlockDriverState *bs, NBDRequest *request,
qemu_mutex_unlock(&s->requests_lock);
qemu_co_mutex_lock(&s->send_mutex);
- request->cookie = INDEX_TO_COOKIE(s, i);
+ request->cookie = INDEX_TO_COOKIE(i);
assert(s->ioc);
@@ -832,7 +832,7 @@ static coroutine_fn int nbd_co_do_receive_one_chunk(
int *request_ret, QEMUIOVector *qiov, void **payload, Error **errp)
{
int ret;
- int i = COOKIE_TO_INDEX(s, cookie);
+ int i = COOKIE_TO_INDEX(cookie);
void *local_payload = NULL;
NBDStructuredReplyChunk *chunk;
@@ -1038,7 +1038,7 @@ static bool coroutine_fn nbd_reply_chunk_iter_receive(BDRVNBDState
*s,
break_loop:
qemu_mutex_lock(&s->requests_lock);
- s->requests[COOKIE_TO_INDEX(s, cookie)].coroutine = NULL;
+ s->requests[COOKIE_TO_INDEX(cookie)].coroutine = NULL;
s->in_flight--;
qemu_co_queue_next(&s->free_sema);
qemu_mutex_unlock(&s->requests_lock);
--
2.40.1