blk-mq: avoid a mess of casts for blk_end_sync_rq

Instead of trying to cast a __bitwise 32-bit integer to a larger integer
and then a pointer, just allow a struct with the blk_status_t and the
completion on stack and set the end_io_data to that.  Use the
opportunity to move the code to where it belongs and drop rather
confusing comments.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20220524121530.943123-3-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 31a89d1004b8f9cb4bcc64585e5c555d5e1e718c..28b3e6db98499001876604f3f56ff94e6b949af2 100644 (file)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1151,24 +1151,6 @@ void blk_mq_start_request(struct request *rq)
 }
 EXPORT_SYMBOL(blk_mq_start_request);
 
-/**
- * blk_end_sync_rq - executes a completion event on a request
- * @rq: request to complete
- * @error: end I/O status of the request
- */
-static void blk_end_sync_rq(struct request *rq, blk_status_t error)
-{
-       struct completion *waiting = rq->end_io_data;
-
-       rq->end_io_data = (void *)(uintptr_t)error;
-
-       /*
-        * complete last, if this is a stack request the process (and thus
-        * the rq pointer) could be invalid right after this complete()
-        */
-       complete(waiting);
-}
-
 /*
  * Allow 2x BLK_MAX_REQUEST_COUNT requests on plug queue for multiple
  * queues. This is important for md arrays to benefit from merging
@@ -1231,6 +1213,19 @@ void blk_execute_rq_nowait(struct request *rq, bool at_head, rq_end_io_fn *done)
 }
 EXPORT_SYMBOL_GPL(blk_execute_rq_nowait);
 
+struct blk_rq_wait {
+       struct completion done;
+       blk_status_t ret;
+};
+
+static void blk_end_sync_rq(struct request *rq, blk_status_t ret)
+{
+       struct blk_rq_wait *wait = rq->end_io_data;
+
+       wait->ret = ret;
+       complete(&wait->done);
+}
+
 static bool blk_rq_is_poll(struct request *rq)
 {
        if (!rq->mq_hctx)
@@ -1262,7 +1257,9 @@ static void blk_rq_poll_completion(struct request *rq, struct completion *wait)
  */
 blk_status_t blk_execute_rq(struct request *rq, bool at_head)
 {
-       DECLARE_COMPLETION_ONSTACK(wait);
+       struct blk_rq_wait wait = {
+               .done = COMPLETION_INITIALIZER_ONSTACK(wait.done),
+       };
 
        WARN_ON(irqs_disabled());
        WARN_ON(!blk_rq_is_passthrough(rq));
@@ -1274,7 +1271,7 @@ blk_status_t blk_execute_rq(struct request *rq, bool at_head)
        blk_mq_sched_insert_request(rq, at_head, true, false);
 
        if (blk_rq_is_poll(rq)) {
-               blk_rq_poll_completion(rq, &wait);
+               blk_rq_poll_completion(rq, &wait.done);
        } else {
                /*
                 * Prevent hang_check timer from firing at us during very long
@@ -1283,14 +1280,14 @@ blk_status_t blk_execute_rq(struct request *rq, bool at_head)
                unsigned long hang_check = sysctl_hung_task_timeout_secs;
 
                if (hang_check)
-                       while (!wait_for_completion_io_timeout(&wait,
+                       while (!wait_for_completion_io_timeout(&wait.done,
                                        hang_check * (HZ/2)))
                                ;
                else
-                       wait_for_completion_io(&wait);
+                       wait_for_completion_io(&wait.done);
        }
 
-       return (blk_status_t)(uintptr_t)rq->end_io_data;
+       return wait.ret;
 }
 EXPORT_SYMBOL(blk_execute_rq);