Adding upstream version 4.19.249.upstream/4.19.249

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1010 insertions, 0 deletions

diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c
new file mode 100644
index 000000000..a5ea86835
--- /dev/null
+++ b/block/blk-mq-debugfs.c
@@ -0,0 +1,1010 @@
+/*
+ * Copyright (C) 2017 Facebook
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <linux/kernel.h>
+#include <linux/blkdev.h>
+#include <linux/debugfs.h>
+
+#include <linux/blk-mq.h>
+#include "blk.h"
+#include "blk-mq.h"
+#include "blk-mq-debugfs.h"
+#include "blk-mq-tag.h"
+
+static void print_stat(struct seq_file *m, struct blk_rq_stat *stat)
+{
+	if (stat->nr_samples) {
+		seq_printf(m, "samples=%d, mean=%lld, min=%llu, max=%llu",
+			   stat->nr_samples, stat->mean, stat->min, stat->max);
+	} else {
+		seq_puts(m, "samples=0");
+	}
+}
+
+static int queue_poll_stat_show(void *data, struct seq_file *m)
+{
+	struct request_queue *q = data;
+	int bucket;
+
+	for (bucket = 0; bucket < BLK_MQ_POLL_STATS_BKTS/2; bucket++) {
+		seq_printf(m, "read  (%d Bytes): ", 1 << (9+bucket));
+		print_stat(m, &q->poll_stat[2*bucket]);
+		seq_puts(m, "\n");
+
+		seq_printf(m, "write (%d Bytes): ",  1 << (9+bucket));
+		print_stat(m, &q->poll_stat[2*bucket+1]);
+		seq_puts(m, "\n");
+	}
+	return 0;
+}
+
+static void *queue_requeue_list_start(struct seq_file *m, loff_t *pos)
+	__acquires(&q->requeue_lock)
+{
+	struct request_queue *q = m->private;
+
+	spin_lock_irq(&q->requeue_lock);
+	return seq_list_start(&q->requeue_list, *pos);
+}
+
+static void *queue_requeue_list_next(struct seq_file *m, void *v, loff_t *pos)
+{
+	struct request_queue *q = m->private;
+
+	return seq_list_next(v, &q->requeue_list, pos);
+}
+
+static void queue_requeue_list_stop(struct seq_file *m, void *v)
+	__releases(&q->requeue_lock)
+{
+	struct request_queue *q = m->private;
+
+	spin_unlock_irq(&q->requeue_lock);
+}
+
+static const struct seq_operations queue_requeue_list_seq_ops = {
+	.start	= queue_requeue_list_start,
+	.next	= queue_requeue_list_next,
+	.stop	= queue_requeue_list_stop,
+	.show	= blk_mq_debugfs_rq_show,
+};
+
+static int blk_flags_show(struct seq_file *m, const unsigned long flags,
+			  const char *const *flag_name, int flag_name_count)
+{
+	bool sep = false;
+	int i;
+
+	for (i = 0; i < sizeof(flags) * BITS_PER_BYTE; i++) {
+		if (!(flags & BIT(i)))
+			continue;
+		if (sep)
+			seq_puts(m, "|");
+		sep = true;
+		if (i < flag_name_count && flag_name[i])
+			seq_puts(m, flag_name[i]);
+		else
+			seq_printf(m, "%d", i);
+	}
+	return 0;
+}
+
+static int queue_pm_only_show(void *data, struct seq_file *m)
+{
+	struct request_queue *q = data;
+
+	seq_printf(m, "%d\n", atomic_read(&q->pm_only));
+	return 0;
+}
+
+#define QUEUE_FLAG_NAME(name) [QUEUE_FLAG_##name] = #name
+static const char *const blk_queue_flag_name[] = {
+	QUEUE_FLAG_NAME(QUEUED),
+	QUEUE_FLAG_NAME(STOPPED),
+	QUEUE_FLAG_NAME(DYING),
+	QUEUE_FLAG_NAME(BYPASS),
+	QUEUE_FLAG_NAME(BIDI),
+	QUEUE_FLAG_NAME(NOMERGES),
+	QUEUE_FLAG_NAME(SAME_COMP),
+	QUEUE_FLAG_NAME(FAIL_IO),
+	QUEUE_FLAG_NAME(NONROT),
+	QUEUE_FLAG_NAME(IO_STAT),
+	QUEUE_FLAG_NAME(DISCARD),
+	QUEUE_FLAG_NAME(NOXMERGES),
+	QUEUE_FLAG_NAME(ADD_RANDOM),
+	QUEUE_FLAG_NAME(SECERASE),
+	QUEUE_FLAG_NAME(SAME_FORCE),
+	QUEUE_FLAG_NAME(DEAD),
+	QUEUE_FLAG_NAME(INIT_DONE),
+	QUEUE_FLAG_NAME(NO_SG_MERGE),
+	QUEUE_FLAG_NAME(POLL),
+	QUEUE_FLAG_NAME(WC),
+	QUEUE_FLAG_NAME(FUA),
+	QUEUE_FLAG_NAME(FLUSH_NQ),
+	QUEUE_FLAG_NAME(DAX),
+	QUEUE_FLAG_NAME(STATS),
+	QUEUE_FLAG_NAME(POLL_STATS),
+	QUEUE_FLAG_NAME(REGISTERED),
+	QUEUE_FLAG_NAME(SCSI_PASSTHROUGH),
+	QUEUE_FLAG_NAME(QUIESCED),
+};
+#undef QUEUE_FLAG_NAME
+
+static int queue_state_show(void *data, struct seq_file *m)
+{
+	struct request_queue *q = data;
+
+	blk_flags_show(m, q->queue_flags, blk_queue_flag_name,
+		       ARRAY_SIZE(blk_queue_flag_name));
+	seq_puts(m, "\n");
+	return 0;
+}
+
+static ssize_t queue_state_write(void *data, const char __user *buf,
+				 size_t count, loff_t *ppos)
+{
+	struct request_queue *q = data;
+	char opbuf[16] = { }, *op;
+
+	/*
+	 * The "state" attribute is removed after blk_cleanup_queue() has called
+	 * blk_mq_free_queue(). Return if QUEUE_FLAG_DEAD has been set to avoid
+	 * triggering a use-after-free.
+	 */
+	if (blk_queue_dead(q))
+		return -ENOENT;
+
+	if (count >= sizeof(opbuf)) {
+		pr_err("%s: operation too long\n", __func__);
+		goto inval;
+	}
+
+	if (copy_from_user(opbuf, buf, count))
+		return -EFAULT;
+	op = strstrip(opbuf);
+	if (strcmp(op, "run") == 0) {
+		blk_mq_run_hw_queues(q, true);
+	} else if (strcmp(op, "start") == 0) {
+		blk_mq_start_stopped_hw_queues(q, true);
+	} else if (strcmp(op, "kick") == 0) {
+		blk_mq_kick_requeue_list(q);
+	} else {
+		pr_err("%s: unsupported operation '%s'\n", __func__, op);
+inval:
+		pr_err("%s: use 'run', 'start' or 'kick'\n", __func__);
+		return -EINVAL;
+	}
+	return count;
+}
+
+static int queue_write_hint_show(void *data, struct seq_file *m)
+{
+	struct request_queue *q = data;
+	int i;
+
+	for (i = 0; i < BLK_MAX_WRITE_HINTS; i++)
+		seq_printf(m, "hint%d: %llu\n", i, q->write_hints[i]);
+
+	return 0;
+}
+
+static ssize_t queue_write_hint_store(void *data, const char __user *buf,
+				      size_t count, loff_t *ppos)
+{
+	struct request_queue *q = data;
+	int i;
+
+	for (i = 0; i < BLK_MAX_WRITE_HINTS; i++)
+		q->write_hints[i] = 0;
+
+	return count;
+}
+
+static const struct blk_mq_debugfs_attr blk_mq_debugfs_queue_attrs[] = {
+	{ "poll_stat", 0400, queue_poll_stat_show },
+	{ "requeue_list", 0400, .seq_ops = &queue_requeue_list_seq_ops },
+	{ "pm_only", 0600, queue_pm_only_show, NULL },
+	{ "state", 0600, queue_state_show, queue_state_write },
+	{ "write_hints", 0600, queue_write_hint_show, queue_write_hint_store },
+	{ "zone_wlock", 0400, queue_zone_wlock_show, NULL },
+	{ },
+};
+
+#define HCTX_STATE_NAME(name) [BLK_MQ_S_##name] = #name
+static const char *const hctx_state_name[] = {
+	HCTX_STATE_NAME(STOPPED),
+	HCTX_STATE_NAME(TAG_ACTIVE),
+	HCTX_STATE_NAME(SCHED_RESTART),
+};
+#undef HCTX_STATE_NAME
+
+static int hctx_state_show(void *data, struct seq_file *m)
+{
+	struct blk_mq_hw_ctx *hctx = data;
+
+	blk_flags_show(m, hctx->state, hctx_state_name,
+		       ARRAY_SIZE(hctx_state_name));
+	seq_puts(m, "\n");
+	return 0;
+}
+
+#define BLK_TAG_ALLOC_NAME(name) [BLK_TAG_ALLOC_##name] = #name
+static const char *const alloc_policy_name[] = {
+	BLK_TAG_ALLOC_NAME(FIFO),
+	BLK_TAG_ALLOC_NAME(RR),
+};
+#undef BLK_TAG_ALLOC_NAME
+
+#define HCTX_FLAG_NAME(name) [ilog2(BLK_MQ_F_##name)] = #name
+static const char *const hctx_flag_name[] = {
+	HCTX_FLAG_NAME(SHOULD_MERGE),
+	HCTX_FLAG_NAME(TAG_SHARED),
+	HCTX_FLAG_NAME(SG_MERGE),
+	HCTX_FLAG_NAME(BLOCKING),
+	HCTX_FLAG_NAME(NO_SCHED),
+};
+#undef HCTX_FLAG_NAME
+
+static int hctx_flags_show(void *data, struct seq_file *m)
+{
+	struct blk_mq_hw_ctx *hctx = data;
+	const int alloc_policy = BLK_MQ_FLAG_TO_ALLOC_POLICY(hctx->flags);
+
+	seq_puts(m, "alloc_policy=");
+	if (alloc_policy < ARRAY_SIZE(alloc_policy_name) &&
+	    alloc_policy_name[alloc_policy])
+		seq_puts(m, alloc_policy_name[alloc_policy]);
+	else
+		seq_printf(m, "%d", alloc_policy);
+	seq_puts(m, " ");
+	blk_flags_show(m,
+		       hctx->flags ^ BLK_ALLOC_POLICY_TO_MQ_FLAG(alloc_policy),
+		       hctx_flag_name, ARRAY_SIZE(hctx_flag_name));
+	seq_puts(m, "\n");
+	return 0;
+}
+
+#define REQ_OP_NAME(name) [REQ_OP_##name] = #name
+static const char *const op_name[] = {
+	REQ_OP_NAME(READ),
+	REQ_OP_NAME(WRITE),
+	REQ_OP_NAME(FLUSH),
+	REQ_OP_NAME(DISCARD),
+	REQ_OP_NAME(ZONE_REPORT),
+	REQ_OP_NAME(SECURE_ERASE),
+	REQ_OP_NAME(ZONE_RESET),
+	REQ_OP_NAME(WRITE_SAME),
+	REQ_OP_NAME(WRITE_ZEROES),
+	REQ_OP_NAME(SCSI_IN),
+	REQ_OP_NAME(SCSI_OUT),
+	REQ_OP_NAME(DRV_IN),
+	REQ_OP_NAME(DRV_OUT),
+};
+#undef REQ_OP_NAME
+
+#define CMD_FLAG_NAME(name) [__REQ_##name] = #name
+static const char *const cmd_flag_name[] = {
+	CMD_FLAG_NAME(FAILFAST_DEV),
+	CMD_FLAG_NAME(FAILFAST_TRANSPORT),
+	CMD_FLAG_NAME(FAILFAST_DRIVER),
+	CMD_FLAG_NAME(SYNC),
+	CMD_FLAG_NAME(META),
+	CMD_FLAG_NAME(PRIO),
+	CMD_FLAG_NAME(NOMERGE),
+	CMD_FLAG_NAME(IDLE),
+	CMD_FLAG_NAME(INTEGRITY),
+	CMD_FLAG_NAME(FUA),
+	CMD_FLAG_NAME(PREFLUSH),
+	CMD_FLAG_NAME(RAHEAD),
+	CMD_FLAG_NAME(BACKGROUND),
+	CMD_FLAG_NAME(NOUNMAP),
+	CMD_FLAG_NAME(NOWAIT),
+};
+#undef CMD_FLAG_NAME
+
+#define RQF_NAME(name) [ilog2((__force u32)RQF_##name)] = #name
+static const char *const rqf_name[] = {
+	RQF_NAME(SORTED),
+	RQF_NAME(STARTED),
+	RQF_NAME(QUEUED),
+	RQF_NAME(SOFTBARRIER),
+	RQF_NAME(FLUSH_SEQ),
+	RQF_NAME(MIXED_MERGE),
+	RQF_NAME(MQ_INFLIGHT),
+	RQF_NAME(DONTPREP),
+	RQF_NAME(PREEMPT),
+	RQF_NAME(COPY_USER),
+	RQF_NAME(FAILED),
+	RQF_NAME(QUIET),
+	RQF_NAME(ELVPRIV),
+	RQF_NAME(IO_STAT),
+	RQF_NAME(ALLOCED),
+	RQF_NAME(PM),
+	RQF_NAME(HASHED),
+	RQF_NAME(STATS),
+	RQF_NAME(SPECIAL_PAYLOAD),
+	RQF_NAME(ZONE_WRITE_LOCKED),
+	RQF_NAME(MQ_POLL_SLEPT),
+};
+#undef RQF_NAME
+
+static const char *const blk_mq_rq_state_name_array[] = {
+	[MQ_RQ_IDLE]		= "idle",
+	[MQ_RQ_IN_FLIGHT]	= "in_flight",
+	[MQ_RQ_COMPLETE]	= "complete",
+};
+
+static const char *blk_mq_rq_state_name(enum mq_rq_state rq_state)
+{
+	if (WARN_ON_ONCE((unsigned int)rq_state >=
+			 ARRAY_SIZE(blk_mq_rq_state_name_array)))
+		return "(?)";
+	return blk_mq_rq_state_name_array[rq_state];
+}
+
+int __blk_mq_debugfs_rq_show(struct seq_file *m, struct request *rq)
+{
+	const struct blk_mq_ops *const mq_ops = rq->q->mq_ops;
+	const unsigned int op = rq->cmd_flags & REQ_OP_MASK;
+
+	seq_printf(m, "%p {.op=", rq);
+	if (op < ARRAY_SIZE(op_name) && op_name[op])
+		seq_printf(m, "%s", op_name[op]);
+	else
+		seq_printf(m, "%d", op);
+	seq_puts(m, ", .cmd_flags=");
+	blk_flags_show(m, rq->cmd_flags & ~REQ_OP_MASK, cmd_flag_name,
+		       ARRAY_SIZE(cmd_flag_name));
+	seq_puts(m, ", .rq_flags=");
+	blk_flags_show(m, (__force unsigned int)rq->rq_flags, rqf_name,
+		       ARRAY_SIZE(rqf_name));
+	seq_printf(m, ", .state=%s", blk_mq_rq_state_name(blk_mq_rq_state(rq)));
+	seq_printf(m, ", .tag=%d, .internal_tag=%d", rq->tag,
+		   rq->internal_tag);
+	if (mq_ops->show_rq)
+		mq_ops->show_rq(m, rq);
+	seq_puts(m, "}\n");
+	return 0;
+}
+EXPORT_SYMBOL_GPL(__blk_mq_debugfs_rq_show);
+
+int blk_mq_debugfs_rq_show(struct seq_file *m, void *v)
+{
+	return __blk_mq_debugfs_rq_show(m, list_entry_rq(v));
+}
+EXPORT_SYMBOL_GPL(blk_mq_debugfs_rq_show);
+
+static void *hctx_dispatch_start(struct seq_file *m, loff_t *pos)
+	__acquires(&hctx->lock)
+{
+	struct blk_mq_hw_ctx *hctx = m->private;
+
+	spin_lock(&hctx->lock);
+	return seq_list_start(&hctx->dispatch, *pos);
+}
+
+static void *hctx_dispatch_next(struct seq_file *m, void *v, loff_t *pos)
+{
+	struct blk_mq_hw_ctx *hctx = m->private;
+
+	return seq_list_next(v, &hctx->dispatch, pos);
+}
+
+static void hctx_dispatch_stop(struct seq_file *m, void *v)
+	__releases(&hctx->lock)
+{
+	struct blk_mq_hw_ctx *hctx = m->private;
+
+	spin_unlock(&hctx->lock);
+}
+
+static const struct seq_operations hctx_dispatch_seq_ops = {
+	.start	= hctx_dispatch_start,
+	.next	= hctx_dispatch_next,
+	.stop	= hctx_dispatch_stop,
+	.show	= blk_mq_debugfs_rq_show,
+};
+
+struct show_busy_params {
+	struct seq_file		*m;
+	struct blk_mq_hw_ctx	*hctx;
+};
+
+/*
+ * Note: the state of a request may change while this function is in progress,
+ * e.g. due to a concurrent blk_mq_finish_request() call.
+ */
+static void hctx_show_busy_rq(struct request *rq, void *data, bool reserved)
+{
+	const struct show_busy_params *params = data;
+
+	if (blk_mq_map_queue(rq->q, rq->mq_ctx->cpu) == params->hctx &&
+	    blk_mq_rq_state(rq) != MQ_RQ_IDLE)
+		__blk_mq_debugfs_rq_show(params->m,
+					 list_entry_rq(&rq->queuelist));
+}
+
+static int hctx_busy_show(void *data, struct seq_file *m)
+{
+	struct blk_mq_hw_ctx *hctx = data;
+	struct show_busy_params params = { .m = m, .hctx = hctx };
+
+	blk_mq_tagset_busy_iter(hctx->queue->tag_set, hctx_show_busy_rq,
+				&params);
+
+	return 0;
+}
+
+static int hctx_ctx_map_show(void *data, struct seq_file *m)
+{
+	struct blk_mq_hw_ctx *hctx = data;
+
+	sbitmap_bitmap_show(&hctx->ctx_map, m);
+	return 0;
+}
+
+static void blk_mq_debugfs_tags_show(struct seq_file *m,
+				     struct blk_mq_tags *tags)
+{
+	seq_printf(m, "nr_tags=%u\n", tags->nr_tags);
+	seq_printf(m, "nr_reserved_tags=%u\n", tags->nr_reserved_tags);
+	seq_printf(m, "active_queues=%d\n",
+		   atomic_read(&tags->active_queues));
+
+	seq_puts(m, "\nbitmap_tags:\n");
+	sbitmap_queue_show(&tags->bitmap_tags, m);
+
+	if (tags->nr_reserved_tags) {
+		seq_puts(m, "\nbreserved_tags:\n");
+		sbitmap_queue_show(&tags->breserved_tags, m);
+	}
+}
+
+static int hctx_tags_show(void *data, struct seq_file *m)
+{
+	struct blk_mq_hw_ctx *hctx = data;
+	struct request_queue *q = hctx->queue;
+	int res;
+
+	res = mutex_lock_interruptible(&q->sysfs_lock);
+	if (res)
+		goto out;
+	if (hctx->tags)
+		blk_mq_debugfs_tags_show(m, hctx->tags);
+	mutex_unlock(&q->sysfs_lock);
+
+out:
+	return res;
+}
+
+static int hctx_tags_bitmap_show(void *data, struct seq_file *m)
+{
+	struct blk_mq_hw_ctx *hctx = data;
+	struct request_queue *q = hctx->queue;
+	int res;
+
+	res = mutex_lock_interruptible(&q->sysfs_lock);
+	if (res)
+		goto out;
+	if (hctx->tags)
+		sbitmap_bitmap_show(&hctx->tags->bitmap_tags.sb, m);
+	mutex_unlock(&q->sysfs_lock);
+
+out:
+	return res;
+}
+
+static int hctx_sched_tags_show(void *data, struct seq_file *m)
+{
+	struct blk_mq_hw_ctx *hctx = data;
+	struct request_queue *q = hctx->queue;
+	int res;
+
+	res = mutex_lock_interruptible(&q->sysfs_lock);
+	if (res)
+		goto out;
+	if (hctx->sched_tags)
+		blk_mq_debugfs_tags_show(m, hctx->sched_tags);
+	mutex_unlock(&q->sysfs_lock);
+
+out:
+	return res;
+}
+
+static int hctx_sched_tags_bitmap_show(void *data, struct seq_file *m)
+{
+	struct blk_mq_hw_ctx *hctx = data;
+	struct request_queue *q = hctx->queue;
+	int res;
+
+	res = mutex_lock_interruptible(&q->sysfs_lock);
+	if (res)
+		goto out;
+	if (hctx->sched_tags)
+		sbitmap_bitmap_show(&hctx->sched_tags->bitmap_tags.sb, m);
+	mutex_unlock(&q->sysfs_lock);
+
+out:
+	return res;
+}
+
+static int hctx_io_poll_show(void *data, struct seq_file *m)
+{
+	struct blk_mq_hw_ctx *hctx = data;
+
+	seq_printf(m, "considered=%lu\n", hctx->poll_considered);
+	seq_printf(m, "invoked=%lu\n", hctx->poll_invoked);
+	seq_printf(m, "success=%lu\n", hctx->poll_success);
+	return 0;
+}
+
+static ssize_t hctx_io_poll_write(void *data, const char __user *buf,
+				  size_t count, loff_t *ppos)
+{
+	struct blk_mq_hw_ctx *hctx = data;
+
+	hctx->poll_considered = hctx->poll_invoked = hctx->poll_success = 0;
+	return count;
+}
+
+static int hctx_dispatched_show(void *data, struct seq_file *m)
+{
+	struct blk_mq_hw_ctx *hctx = data;
+	int i;
+
+	seq_printf(m, "%8u\t%lu\n", 0U, hctx->dispatched[0]);
+
+	for (i = 1; i < BLK_MQ_MAX_DISPATCH_ORDER - 1; i++) {
+		unsigned int d = 1U << (i - 1);
+
+		seq_printf(m, "%8u\t%lu\n", d, hctx->dispatched[i]);
+	}
+
+	seq_printf(m, "%8u+\t%lu\n", 1U << (i - 1), hctx->dispatched[i]);
+	return 0;
+}
+
+static ssize_t hctx_dispatched_write(void *data, const char __user *buf,
+				     size_t count, loff_t *ppos)
+{
+	struct blk_mq_hw_ctx *hctx = data;
+	int i;
+
+	for (i = 0; i < BLK_MQ_MAX_DISPATCH_ORDER; i++)
+		hctx->dispatched[i] = 0;
+	return count;
+}
+
+static int hctx_queued_show(void *data, struct seq_file *m)
+{
+	struct blk_mq_hw_ctx *hctx = data;
+
+	seq_printf(m, "%lu\n", hctx->queued);
+	return 0;
+}
+
+static ssize_t hctx_queued_write(void *data, const char __user *buf,
+				 size_t count, loff_t *ppos)
+{
+	struct blk_mq_hw_ctx *hctx = data;
+
+	hctx->queued = 0;
+	return count;
+}
+
+static int hctx_run_show(void *data, struct seq_file *m)
+{
+	struct blk_mq_hw_ctx *hctx = data;
+
+	seq_printf(m, "%lu\n", hctx->run);
+	return 0;
+}
+
+static ssize_t hctx_run_write(void *data, const char __user *buf, size_t count,
+			      loff_t *ppos)
+{
+	struct blk_mq_hw_ctx *hctx = data;
+
+	hctx->run = 0;
+	return count;
+}
+
+static int hctx_active_show(void *data, struct seq_file *m)
+{
+	struct blk_mq_hw_ctx *hctx = data;
+
+	seq_printf(m, "%d\n", atomic_read(&hctx->nr_active));
+	return 0;
+}
+
+static int hctx_dispatch_busy_show(void *data, struct seq_file *m)
+{
+	struct blk_mq_hw_ctx *hctx = data;
+
+	seq_printf(m, "%u\n", hctx->dispatch_busy);
+	return 0;
+}
+
+static void *ctx_rq_list_start(struct seq_file *m, loff_t *pos)
+	__acquires(&ctx->lock)
+{
+	struct blk_mq_ctx *ctx = m->private;
+
+	spin_lock(&ctx->lock);
+	return seq_list_start(&ctx->rq_list, *pos);
+}
+
+static void *ctx_rq_list_next(struct seq_file *m, void *v, loff_t *pos)
+{
+	struct blk_mq_ctx *ctx = m->private;
+
+	return seq_list_next(v, &ctx->rq_list, pos);
+}
+
+static void ctx_rq_list_stop(struct seq_file *m, void *v)
+	__releases(&ctx->lock)
+{
+	struct blk_mq_ctx *ctx = m->private;
+
+	spin_unlock(&ctx->lock);
+}
+
+static const struct seq_operations ctx_rq_list_seq_ops = {
+	.start	= ctx_rq_list_start,
+	.next	= ctx_rq_list_next,
+	.stop	= ctx_rq_list_stop,
+	.show	= blk_mq_debugfs_rq_show,
+};
+static int ctx_dispatched_show(void *data, struct seq_file *m)
+{
+	struct blk_mq_ctx *ctx = data;
+
+	seq_printf(m, "%lu %lu\n", ctx->rq_dispatched[1], ctx->rq_dispatched[0]);
+	return 0;
+}
+
+static ssize_t ctx_dispatched_write(void *data, const char __user *buf,
+				    size_t count, loff_t *ppos)
+{
+	struct blk_mq_ctx *ctx = data;
+
+	ctx->rq_dispatched[0] = ctx->rq_dispatched[1] = 0;
+	return count;
+}
+
+static int ctx_merged_show(void *data, struct seq_file *m)
+{
+	struct blk_mq_ctx *ctx = data;
+
+	seq_printf(m, "%lu\n", ctx->rq_merged);
+	return 0;
+}
+
+static ssize_t ctx_merged_write(void *data, const char __user *buf,
+				size_t count, loff_t *ppos)
+{
+	struct blk_mq_ctx *ctx = data;
+
+	ctx->rq_merged = 0;
+	return count;
+}
+
+static int ctx_completed_show(void *data, struct seq_file *m)
+{
+	struct blk_mq_ctx *ctx = data;
+
+	seq_printf(m, "%lu %lu\n", ctx->rq_completed[1], ctx->rq_completed[0]);
+	return 0;
+}
+
+static ssize_t ctx_completed_write(void *data, const char __user *buf,
+				   size_t count, loff_t *ppos)
+{
+	struct blk_mq_ctx *ctx = data;
+
+	ctx->rq_completed[0] = ctx->rq_completed[1] = 0;
+	return count;
+}
+
+static int blk_mq_debugfs_show(struct seq_file *m, void *v)
+{
+	const struct blk_mq_debugfs_attr *attr = m->private;
+	void *data = d_inode(m->file->f_path.dentry->d_parent)->i_private;
+
+	return attr->show(data, m);
+}
+
+static ssize_t blk_mq_debugfs_write(struct file *file, const char __user *buf,
+				    size_t count, loff_t *ppos)
+{
+	struct seq_file *m = file->private_data;
+	const struct blk_mq_debugfs_attr *attr = m->private;
+	void *data = d_inode(file->f_path.dentry->d_parent)->i_private;
+
+	/*
+	 * Attributes that only implement .seq_ops are read-only and 'attr' is
+	 * the same with 'data' in this case.
+	 */
+	if (attr == data || !attr->write)
+		return -EPERM;
+
+	return attr->write(data, buf, count, ppos);
+}
+
+static int blk_mq_debugfs_open(struct inode *inode, struct file *file)
+{
+	const struct blk_mq_debugfs_attr *attr = inode->i_private;
+	void *data = d_inode(file->f_path.dentry->d_parent)->i_private;
+	struct seq_file *m;
+	int ret;
+
+	if (attr->seq_ops) {
+		ret = seq_open(file, attr->seq_ops);
+		if (!ret) {
+			m = file->private_data;
+			m->private = data;
+		}
+		return ret;
+	}
+
+	if (WARN_ON_ONCE(!attr->show))
+		return -EPERM;
+
+	return single_open(file, blk_mq_debugfs_show, inode->i_private);
+}
+
+static int blk_mq_debugfs_release(struct inode *inode, struct file *file)
+{
+	const struct blk_mq_debugfs_attr *attr = inode->i_private;
+
+	if (attr->show)
+		return single_release(inode, file);
+	else
+		return seq_release(inode, file);
+}
+
+static const struct file_operations blk_mq_debugfs_fops = {
+	.open		= blk_mq_debugfs_open,
+	.read		= seq_read,
+	.write		= blk_mq_debugfs_write,
+	.llseek		= seq_lseek,
+	.release	= blk_mq_debugfs_release,
+};
+
+static const struct blk_mq_debugfs_attr blk_mq_debugfs_hctx_attrs[] = {
+	{"state", 0400, hctx_state_show},
+	{"flags", 0400, hctx_flags_show},
+	{"dispatch", 0400, .seq_ops = &hctx_dispatch_seq_ops},
+	{"busy", 0400, hctx_busy_show},
+	{"ctx_map", 0400, hctx_ctx_map_show},
+	{"tags", 0400, hctx_tags_show},
+	{"tags_bitmap", 0400, hctx_tags_bitmap_show},
+	{"sched_tags", 0400, hctx_sched_tags_show},
+	{"sched_tags_bitmap", 0400, hctx_sched_tags_bitmap_show},
+	{"io_poll", 0600, hctx_io_poll_show, hctx_io_poll_write},
+	{"dispatched", 0600, hctx_dispatched_show, hctx_dispatched_write},
+	{"queued", 0600, hctx_queued_show, hctx_queued_write},
+	{"run", 0600, hctx_run_show, hctx_run_write},
+	{"active", 0400, hctx_active_show},
+	{"dispatch_busy", 0400, hctx_dispatch_busy_show},
+	{},
+};
+
+static const struct blk_mq_debugfs_attr blk_mq_debugfs_ctx_attrs[] = {
+	{"rq_list", 0400, .seq_ops = &ctx_rq_list_seq_ops},
+	{"dispatched", 0600, ctx_dispatched_show, ctx_dispatched_write},
+	{"merged", 0600, ctx_merged_show, ctx_merged_write},
+	{"completed", 0600, ctx_completed_show, ctx_completed_write},
+	{},
+};
+
+static bool debugfs_create_files(struct dentry *parent, void *data,
+				 const struct blk_mq_debugfs_attr *attr)
+{
+	d_inode(parent)->i_private = data;
+
+	for (; attr->name; attr++) {
+		if (!debugfs_create_file(attr->name, attr->mode, parent,
+					 (void *)attr, &blk_mq_debugfs_fops))
+			return false;
+	}
+	return true;
+}
+
+int blk_mq_debugfs_register(struct request_queue *q)
+{
+	struct blk_mq_hw_ctx *hctx;
+	int i;
+
+	if (!blk_debugfs_root)
+		return -ENOENT;
+
+	q->debugfs_dir = debugfs_create_dir(kobject_name(q->kobj.parent),
+					    blk_debugfs_root);
+	if (!q->debugfs_dir)
+		return -ENOMEM;
+
+	if (!debugfs_create_files(q->debugfs_dir, q,
+				  blk_mq_debugfs_queue_attrs))
+		goto err;
+
+	/*
+	 * blk_mq_init_sched() attempted to do this already, but q->debugfs_dir
+	 * didn't exist yet (because we don't know what to name the directory
+	 * until the queue is registered to a gendisk).
+	 */
+	if (q->elevator && !q->sched_debugfs_dir)
+		blk_mq_debugfs_register_sched(q);
+
+	/* Similarly, blk_mq_init_hctx() couldn't do this previously. */
+	queue_for_each_hw_ctx(q, hctx, i) {
+		if (!hctx->debugfs_dir && blk_mq_debugfs_register_hctx(q, hctx))
+			goto err;
+		if (q->elevator && !hctx->sched_debugfs_dir &&
+		    blk_mq_debugfs_register_sched_hctx(q, hctx))
+			goto err;
+	}
+
+	return 0;
+
+err:
+	blk_mq_debugfs_unregister(q);
+	return -ENOMEM;
+}
+
+void blk_mq_debugfs_unregister(struct request_queue *q)
+{
+	debugfs_remove_recursive(q->debugfs_dir);
+	q->sched_debugfs_dir = NULL;
+	q->debugfs_dir = NULL;
+}
+
+static int blk_mq_debugfs_register_ctx(struct blk_mq_hw_ctx *hctx,
+				       struct blk_mq_ctx *ctx)
+{
+	struct dentry *ctx_dir;
+	char name[20];
+
+	snprintf(name, sizeof(name), "cpu%u", ctx->cpu);
+	ctx_dir = debugfs_create_dir(name, hctx->debugfs_dir);
+	if (!ctx_dir)
+		return -ENOMEM;
+
+	if (!debugfs_create_files(ctx_dir, ctx, blk_mq_debugfs_ctx_attrs))
+		return -ENOMEM;
+
+	return 0;
+}
+
+int blk_mq_debugfs_register_hctx(struct request_queue *q,
+				 struct blk_mq_hw_ctx *hctx)
+{
+	struct blk_mq_ctx *ctx;
+	char name[20];
+	int i;
+
+	if (!q->debugfs_dir)
+		return -ENOENT;
+
+	snprintf(name, sizeof(name), "hctx%u", hctx->queue_num);
+	hctx->debugfs_dir = debugfs_create_dir(name, q->debugfs_dir);
+	if (!hctx->debugfs_dir)
+		return -ENOMEM;
+
+	if (!debugfs_create_files(hctx->debugfs_dir, hctx,
+				  blk_mq_debugfs_hctx_attrs))
+		goto err;
+
+	hctx_for_each_ctx(hctx, ctx, i) {
+		if (blk_mq_debugfs_register_ctx(hctx, ctx))
+			goto err;
+	}
+
+	return 0;
+
+err:
+	blk_mq_debugfs_unregister_hctx(hctx);
+	return -ENOMEM;
+}
+
+void blk_mq_debugfs_unregister_hctx(struct blk_mq_hw_ctx *hctx)
+{
+	debugfs_remove_recursive(hctx->debugfs_dir);
+	hctx->sched_debugfs_dir = NULL;
+	hctx->debugfs_dir = NULL;
+}
+
+int blk_mq_debugfs_register_hctxs(struct request_queue *q)
+{
+	struct blk_mq_hw_ctx *hctx;
+	int i;
+
+	queue_for_each_hw_ctx(q, hctx, i) {
+		if (blk_mq_debugfs_register_hctx(q, hctx))
+			return -ENOMEM;
+	}
+
+	return 0;
+}
+
+void blk_mq_debugfs_unregister_hctxs(struct request_queue *q)
+{
+	struct blk_mq_hw_ctx *hctx;
+	int i;
+
+	queue_for_each_hw_ctx(q, hctx, i)
+		blk_mq_debugfs_unregister_hctx(hctx);
+}
+
+int blk_mq_debugfs_register_sched(struct request_queue *q)
+{
+	struct elevator_type *e = q->elevator->type;
+
+	if (!q->debugfs_dir)
+		return -ENOENT;
+
+	if (!e->queue_debugfs_attrs)
+		return 0;
+
+	q->sched_debugfs_dir = debugfs_create_dir("sched", q->debugfs_dir);
+	if (!q->sched_debugfs_dir)
+		return -ENOMEM;
+
+	if (!debugfs_create_files(q->sched_debugfs_dir, q,
+				  e->queue_debugfs_attrs))
+		goto err;
+
+	return 0;
+
+err:
+	blk_mq_debugfs_unregister_sched(q);
+	return -ENOMEM;
+}
+
+void blk_mq_debugfs_unregister_sched(struct request_queue *q)
+{
+	debugfs_remove_recursive(q->sched_debugfs_dir);
+	q->sched_debugfs_dir = NULL;
+}
+
+int blk_mq_debugfs_register_sched_hctx(struct request_queue *q,
+				       struct blk_mq_hw_ctx *hctx)
+{
+	struct elevator_type *e = q->elevator->type;
+
+	if (!hctx->debugfs_dir)
+		return -ENOENT;
+
+	if (!e->hctx_debugfs_attrs)
+		return 0;
+
+	hctx->sched_debugfs_dir = debugfs_create_dir("sched",
+						     hctx->debugfs_dir);
+	if (!hctx->sched_debugfs_dir)
+		return -ENOMEM;
+
+	if (!debugfs_create_files(hctx->sched_debugfs_dir, hctx,
+				  e->hctx_debugfs_attrs))
+		return -ENOMEM;
+
+	return 0;
+}
+
+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;
+}