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/blk-mq-debugfs.c b/block/blk-mq-debugfs.c
new file mode 100644
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);
+}