block, bfq: move io_cq-persistent bfqq data into a dedicated struct

With a multi-actuator drive, a process may get associated with multiple
bfq_queues: one queue for each of the N actuators. So, the bfq_io_cq
data structure must be able to accommodate its per-queue persistent
information for N queues. Currently it stores this information for
just one queue, in several scalar fields.

This is a preparatory commit for moving to accommodating persistent
information for N queues. In particular, this commit packs all the
above scalar fields into a single data structure. Then there is now
only one field, in bfq_io_cq, that stores all the above information. This
scalar field will then be turned into an array by a following commit.
Suggested-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Reviewed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Signed-off-by: Gianmarco Lusvardi <glusvardi@posteo.net>
Signed-off-by: Giulio Barabino <giuliobarabino99@gmail.com>
Signed-off-by: Emiliano Maccaferri <inbox@emilianomaccaferri.com>
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Link: https://lore.kernel.org/r/20230103145503.71712-4-paolo.valente@linaro.orgSigned-off-by: Jens Axboe <axboe@kernel.dk>

block/bfq-iosched.h

@@ -413,27 +413,9 @@ struct bfq_queue {
 };
 
 /**
- * struct bfq_io_cq - per (request_queue, io_context) structure.
- */
-struct bfq_io_cq {
-	/* associated io_cq structure */
-	struct io_cq icq; /* must be the first member */
-	/*
-	 * Matrix of associated process queues: first row for async
-	 * queues, second row sync queues. Each row contains one
-	 * column for each actuator. An I/O request generated by the
-	 * process is inserted into the queue pointed by bfqq[i][j] if
-	 * the request is to be served by the j-th actuator of the
-	 * drive, where i==0 or i==1, depending on whether the request
-	 * is async or sync. So there is a distinct queue for each
-	 * actuator.
-	 */
-	struct bfq_queue *bfqq[2][BFQ_MAX_ACTUATORS];
-	/* per (request_queue, blkcg) ioprio */
-	int ioprio;
-#ifdef CONFIG_BFQ_GROUP_IOSCHED
-	uint64_t blkcg_serial_nr; /* the current blkcg serial */
-#endif
+* struct bfq_data - bfqq data unique and persistent for associated bfq_io_cq
+*/
+struct bfq_iocq_bfqq_data {
 	/*
 	 * Snapshot of the has_short_time flag before merging; taken
 	 * to remember its value while the queue is merged, so as to
@@ -488,6 +470,34 @@ struct bfq_io_cq {
 	struct bfq_queue *stable_merge_bfqq;
 
 	bool stably_merged;	/* non splittable if true */
+};
+
+/**
+ * struct bfq_io_cq - per (request_queue, io_context) structure.
+ */
+struct bfq_io_cq {
+	/* associated io_cq structure */
+	struct io_cq icq; /* must be the first member */
+	/*
+	 * Matrix of associated process queues: first row for async
+	 * queues, second row sync queues. Each row contains one
+	 * column for each actuator. An I/O request generated by the
+	 * process is inserted into the queue pointed by bfqq[i][j] if
+	 * the request is to be served by the j-th actuator of the
+	 * drive, where i==0 or i==1, depending on whether the request
+	 * is async or sync. So there is a distinct queue for each
+	 * actuator.
+	 */
+	struct bfq_queue *bfqq[2][BFQ_MAX_ACTUATORS];
+	/* per (request_queue, blkcg) ioprio */
+	int ioprio;
+#ifdef CONFIG_BFQ_GROUP_IOSCHED
+	uint64_t blkcg_serial_nr; /* the current blkcg serial */
+#endif
+
+	/* persistent data for associated synchronous process queue */
+	struct bfq_iocq_bfqq_data bfqq_data;
+
 	unsigned int requests;	/* Number of requests this process has in flight */
 };