blk-mq: create debugfs directory tree

In preparation for putting blk-mq debugging information in debugfs,
create a directory tree mirroring the one in sysfs:

    # tree -d /sys/kernel/debug/block
    /sys/kernel/debug/block
    |-- nvme0n1
    |   `-- mq
    |       |-- 0
    |       |   `-- cpu0
    |       |-- 1
    |       |   `-- cpu1
    |       |-- 2
    |       |   `-- cpu2
    |       `-- 3
    |           `-- cpu3
    `-- vda
        `-- mq
            `-- 0
                |-- cpu0
                |-- cpu1
                |-- cpu2
                `-- cpu3

Also add the scaffolding for the actual files that will go in here,
either under the hardware queue or software queue directories.

Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

diff --git a/block/Makefile b/block/Makefile
index 3ee0abd7205ad98b723713cfd6b4ee47f3c744a6..6cabe6bd2882c41bc232c72aa7a73e2bdd556962 100644 (file)
--- a/block/Makefile
+++ b/block/Makefile
@@ -26,3 +26,4 @@ obj-$(CONFIG_BLK_DEV_INTEGRITY) += bio-integrity.o blk-integrity.o t10-pi.o
 obj-$(CONFIG_BLK_MQ_PCI)       += blk-mq-pci.o
 obj-$(CONFIG_BLK_DEV_ZONED)    += blk-zoned.o
 obj-$(CONFIG_BLK_WBT)          += blk-wbt.o
+obj-$(CONFIG_DEBUG_FS)         += blk-mq-debugfs.o

diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c
new file mode 100644 (file)
index 0000000..01711bb
--- /dev/null
+++ b/block/blk-mq-debugfs.c
@@ -0,0 +1,152 @@
+/*
+ * 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-mq.h"
+
+struct blk_mq_debugfs_attr {
+       const char *name;
+       umode_t mode;
+       const struct file_operations *fops;
+};
+
+static struct dentry *block_debugfs_root;
+
+static const struct blk_mq_debugfs_attr blk_mq_debugfs_hctx_attrs[] = {
+};
+
+static const struct blk_mq_debugfs_attr blk_mq_debugfs_ctx_attrs[] = {
+};
+
+int blk_mq_debugfs_register(struct request_queue *q, const char *name)
+{
+       if (!block_debugfs_root)
+               return -ENOENT;
+
+       q->debugfs_dir = debugfs_create_dir(name, block_debugfs_root);
+       if (!q->debugfs_dir)
+               goto err;
+
+       if (blk_mq_debugfs_register_hctxs(q))
+               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->mq_debugfs_dir = NULL;
+       q->debugfs_dir = NULL;
+}
+
+static int blk_mq_debugfs_register_ctx(struct request_queue *q,
+                                      struct blk_mq_ctx *ctx,
+                                      struct dentry *hctx_dir)
+{
+       struct dentry *ctx_dir;
+       char name[20];
+       int i;
+
+       snprintf(name, sizeof(name), "cpu%u", ctx->cpu);
+       ctx_dir = debugfs_create_dir(name, hctx_dir);
+       if (!ctx_dir)
+               return -ENOMEM;
+
+       for (i = 0; i < ARRAY_SIZE(blk_mq_debugfs_ctx_attrs); i++) {
+               const struct blk_mq_debugfs_attr *attr;
+
+               attr = &blk_mq_debugfs_ctx_attrs[i];
+               if (!debugfs_create_file(attr->name, attr->mode, ctx_dir, ctx,
+                                        attr->fops))
+                       return -ENOMEM;
+       }
+
+       return 0;
+}
+
+static int blk_mq_debugfs_register_hctx(struct request_queue *q,
+                                       struct blk_mq_hw_ctx *hctx)
+{
+       struct blk_mq_ctx *ctx;
+       struct dentry *hctx_dir;
+       char name[20];
+       int i;
+
+       snprintf(name, sizeof(name), "%u", hctx->queue_num);
+       hctx_dir = debugfs_create_dir(name, q->mq_debugfs_dir);
+       if (!hctx_dir)
+               return -ENOMEM;
+
+       for (i = 0; i < ARRAY_SIZE(blk_mq_debugfs_hctx_attrs); i++) {
+               const struct blk_mq_debugfs_attr *attr;
+
+               attr = &blk_mq_debugfs_hctx_attrs[i];
+               if (!debugfs_create_file(attr->name, attr->mode, hctx_dir, hctx,
+                                        attr->fops))
+                       return -ENOMEM;
+       }
+
+       hctx_for_each_ctx(hctx, ctx, i) {
+               if (blk_mq_debugfs_register_ctx(q, ctx, hctx_dir))
+                       return -ENOMEM;
+       }
+
+       return 0;
+}
+
+int blk_mq_debugfs_register_hctxs(struct request_queue *q)
+{
+       struct blk_mq_hw_ctx *hctx;
+       int i;
+
+       if (!q->debugfs_dir)
+               return -ENOENT;
+
+       q->mq_debugfs_dir = debugfs_create_dir("mq", q->debugfs_dir);
+       if (!q->mq_debugfs_dir)
+               goto err;
+
+       queue_for_each_hw_ctx(q, hctx, i) {
+               if (blk_mq_debugfs_register_hctx(q, hctx))
+                       goto err;
+       }
+
+       return 0;
+
+err:
+       blk_mq_debugfs_unregister_hctxs(q);
+       return -ENOMEM;
+}
+
+void blk_mq_debugfs_unregister_hctxs(struct request_queue *q)
+{
+       debugfs_remove_recursive(q->mq_debugfs_dir);
+       q->mq_debugfs_dir = NULL;
+}
+
+void blk_mq_debugfs_init(void)
+{
+       block_debugfs_root = debugfs_create_dir("block", NULL);
+}

diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c
index 2caecaa98e40bb57dd3c0f43e8f75e3fab7b3701..91b93ca1c1e0ece279191a611a1256f88727798d 100644 (file)
--- a/block/blk-mq-sysfs.c
+++ b/block/blk-mq-sysfs.c
@@ -468,6 +468,8 @@ static void __blk_mq_unregister_dev(struct device *dev, struct request_queue *q)
                kobject_put(&hctx->kobj);
        }
 
+       blk_mq_debugfs_unregister(q);
+
        kobject_uevent(&q->mq_kobj, KOBJ_REMOVE);
        kobject_del(&q->mq_kobj);
        kobject_put(&q->mq_kobj);
@@ -517,6 +519,8 @@ int blk_mq_register_dev(struct device *dev, struct request_queue *q)
 
        kobject_uevent(&q->mq_kobj, KOBJ_ADD);
 
+       blk_mq_debugfs_register(q, kobject_name(&dev->kobj));
+
        queue_for_each_hw_ctx(q, hctx, i) {
                ret = blk_mq_register_hctx(hctx);
                if (ret)
@@ -542,6 +546,8 @@ void blk_mq_sysfs_unregister(struct request_queue *q)
        if (!q->mq_sysfs_init_done)
                return;
 
+       blk_mq_debugfs_unregister_hctxs(q);
+
        queue_for_each_hw_ctx(q, hctx, i)
                blk_mq_unregister_hctx(hctx);
 }
@@ -554,6 +560,8 @@ int blk_mq_sysfs_register(struct request_queue *q)
        if (!q->mq_sysfs_init_done)
                return ret;
 
+       blk_mq_debugfs_register_hctxs(q);
+
        queue_for_each_hw_ctx(q, hctx, i) {
                ret = blk_mq_register_hctx(hctx);
                if (ret)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 84d13b5cafd066f6697eae559b7ee1220c58c349..ede835c2b08baa0fc8f1ded85ac877c73dd2b5df 100644 (file)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2799,6 +2799,8 @@ void blk_mq_enable_hotplug(void)
 
 static int __init blk_mq_init(void)
 {
+       blk_mq_debugfs_init();
+
        cpuhp_setup_state_multi(CPUHP_BLK_MQ_DEAD, "block/mq:dead", NULL,
                                blk_mq_hctx_notify_dead);
 

diff --git a/block/blk-mq.h b/block/blk-mq.h
index 0c7c034d9ddde2e7a211326b36762b9612af0ec2..6c24b901acd764e0c614830884cc91af88b109fd 100644 (file)
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -78,6 +78,39 @@ extern int blk_mq_sysfs_register(struct request_queue *q);
 extern void blk_mq_sysfs_unregister(struct request_queue *q);
 extern void blk_mq_hctx_kobj_init(struct blk_mq_hw_ctx *hctx);
 
+/*
+ * debugfs helpers
+ */
+#ifdef CONFIG_DEBUG_FS
+void blk_mq_debugfs_init(void);
+int blk_mq_debugfs_register(struct request_queue *q, const char *name);
+void blk_mq_debugfs_unregister(struct request_queue *q);
+int blk_mq_debugfs_register_hctxs(struct request_queue *q);
+void blk_mq_debugfs_unregister_hctxs(struct request_queue *q);
+#else
+static inline void blk_mq_debugfs_init(void)
+{
+}
+
+int blk_mq_debugfs_register(struct request_queue *q, const char *name);
+{
+       return 0;
+}
+
+void blk_mq_debugfs_unregister(struct request_queue *q)
+{
+}
+
+int blk_mq_debugfs_register_hctxs(struct request_queue *q)
+{
+       return 0;
+}
+
+void blk_mq_debugfs_unregister_hctxs(struct request_queue *q)
+{
+}
+#endif
+
 extern void blk_mq_rq_timed_out(struct request *req, bool reserved);
 
 void blk_mq_release(struct request_queue *q);

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 25564857f5f8de216c7cef8ed77b1f3c6c57075b..0ee283f3cffe7657cb58bcb65c6c56050f49a570 100644 (file)
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -571,6 +571,11 @@ struct request_queue {
        struct list_head        tag_set_list;
        struct bio_set          *bio_split;
 
+#ifdef CONFIG_DEBUG_FS
+       struct dentry           *debugfs_dir;
+       struct dentry           *mq_debugfs_dir;
+#endif
+
        bool                    mq_sysfs_init_done;
 };