ANDROID: block: Make sub_page_limit_queues available in debugfs

This new debugfs attribute makes it easier to verify the code that tracks
how many queues require limits below the page size.

Bug: 308663717
Bug: 319125789
Change-Id: I2ee54a9e4544866e71b505ae9296b68039d5ca82
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
[jyescas@google.com: Wrap #include "blk-mq-debugfs.h" with
                     #ifndef __GENKSYSM__ to avoid ABI CRC
                     changes.]
Signed-off-by: Juan Yescas <jyescas@google.com>

block/blk-core.c

@@ -45,6 +45,9 @@
 #include <trace/events/block.h>
 
 #include "blk.h"
+#ifndef __GENKSYMS__
+#include "blk-mq-debugfs.h"
+#endif
 #include "blk-mq-sched.h"
 #include "blk-pm.h"
 #include "blk-cgroup.h"
@@ -1213,6 +1216,7 @@ int __init blk_dev_init(void)
 			sizeof(struct srcu_struct), 0, SLAB_PANIC, NULL);
 
 	blk_debugfs_root = debugfs_create_dir("block", NULL);
+	blk_mq_debugfs_init();
 
 	return 0;
 }

block/blk-mq-debugfs.c

@@ -874,3 +874,12 @@ void blk_mq_debugfs_unregister_sched_hctx(struct blk_mq_hw_ctx *hctx)
 	debugfs_remove_recursive(hctx->sched_debugfs_dir);
 	hctx->sched_debugfs_dir = NULL;
 }
+
+DEFINE_DEBUGFS_ATTRIBUTE(blk_sub_page_limit_queues_fops,
+			blk_sub_page_limit_queues_get, NULL, "%llu\n");
+
+void blk_mq_debugfs_init(void)
+{
+	debugfs_create_file("sub_page_limit_queues", 0400, blk_debugfs_root,
+			    NULL, &blk_sub_page_limit_queues_fops);
+}

block/blk-mq-debugfs.h

@@ -17,6 +17,8 @@ struct blk_mq_debugfs_attr {
 	const struct seq_operations *seq_ops;
 };
 
+void blk_mq_debugfs_init(void);
+
 int __blk_mq_debugfs_rq_show(struct seq_file *m, struct request *rq);
 int blk_mq_debugfs_rq_show(struct seq_file *m, void *v);
 
@@ -36,6 +38,10 @@ void blk_mq_debugfs_unregister_sched_hctx(struct blk_mq_hw_ctx *hctx);
 void blk_mq_debugfs_register_rqos(struct rq_qos *rqos);
 void blk_mq_debugfs_unregister_rqos(struct rq_qos *rqos);
 #else
+static inline void blk_mq_debugfs_init(void)
+{
+}
+
 static inline void blk_mq_debugfs_register(struct request_queue *q)
 {
 }

block/blk-settings.c

@@ -109,6 +109,14 @@ void blk_queue_bounce_limit(struct request_queue *q, enum blk_bounce bounce)
 }
 EXPORT_SYMBOL(blk_queue_bounce_limit);
 
+/* For debugfs. */
+int blk_sub_page_limit_queues_get(void *data, u64 *val)
+{
+	*val = READ_ONCE(blk_nr_sub_page_limit_queues);
+
+	return 0;
+}
+
 /**
  * blk_enable_sub_page_limits - enable support for limits below the page size
  * @lim: request queue limits for which to enable support of these features.

block/blk.h

@@ -44,6 +44,7 @@ static inline bool blk_queue_sub_page_limits(const struct queue_limits *lim)
 		lim->sub_page_limits;
 }
 
+int blk_sub_page_limit_queues_get(void *data, u64 *val);
 void blk_disable_sub_page_limits(struct queue_limits *q);
 
 void blk_freeze_queue(struct request_queue *q);