[PATCH 3/4] io_uring/cmd: add per-op data to struct io_uring_cmd_data

[Mark Harmstone <maharmstone@fb.com>]

From: Jens Axboe <axboe@kernel.dk>

In case an op handler for ->uring_cmd() needs stable storage for user
data, it can allocate io_uring_cmd_data->op_data and use it for the
duration of the request. When the request gets cleaned up, uring_cmd
will free it automatically.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 include/linux/io_uring/cmd.h |  1 +
 io_uring/uring_cmd.c         | 13 +++++++++++--
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/include/linux/io_uring/cmd.h b/include/linux/io_uring/cmd.h
index 24cff2b9b9d4..3df6636ec3a3 100644
--- a/include/linux/io_uring/cmd.h
+++ b/include/linux/io_uring/cmd.h
@@ -20,6 +20,7 @@ struct io_uring_cmd {
 
 struct io_uring_cmd_data {
 	struct io_uring_sqe	sqes[2];
+	void			*op_data;
 };
 
 static inline const void *io_uring_sqe_cmd(const struct io_uring_sqe *sqe)
diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c
index eefc203a1214..019d6f49ff20 100644
--- a/io_uring/uring_cmd.c
+++ b/io_uring/uring_cmd.c
@@ -23,12 +23,16 @@ static struct io_uring_cmd_data *io_uring_async_get(struct io_kiocb *req)
 
 	cache = io_alloc_cache_get(&ctx->uring_cache);
 	if (cache) {
+		cache->op_data = NULL;
 		req->flags |= REQ_F_ASYNC_DATA;
 		req->async_data = cache;
 		return cache;
 	}
-	if (!io_alloc_async_data(req))
-		return req->async_data;
+	if (!io_alloc_async_data(req)) {
+		cache = req->async_data;
+		cache->op_data = NULL;
+		return cache;
+	}
 	return NULL;
 }
 
@@ -37,6 +41,11 @@ static void io_req_uring_cleanup(struct io_kiocb *req, unsigned int issue_flags)
 	struct io_uring_cmd *ioucmd = io_kiocb_to_cmd(req, struct io_uring_cmd);
 	struct io_uring_cmd_data *cache = req->async_data;
 
+	if (cache->op_data) {
+		kfree(cache->op_data);
+		cache->op_data = NULL;
+	}
+
 	if (issue_flags & IO_URING_F_UNLOCKED)
 		return;
 	if (io_alloc_cache_put(&req->ctx->uring_cache, cache)) {
-- 
2.45.2