On Wed, Feb 01, 2023 at 02:01:18PM -0800, Bart Van Assche wrote:

On 2/1/23 13:23, Luis Chamberlain wrote:

quoted

On Wed, Feb 01, 2023 at 12:58:00PM -0800, Luis Chamberlain wrote:

quoted

On Mon, Jan 30, 2023 at 01:26:50PM -0800, Bart Van Assche wrote:

quoted

Move the code for creating the block layer debugfs root directory into
blk-mq-debugfs.c. This patch prepares for adding more debugfs
initialization code by introducing the function blk_mq_debugfs_init().

Cc: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <redacted>
Cc: Keith Busch <kbusch@kernel.org>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>

Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>

Sorry but actually a neuron triggered after this to remind me of commit
85e0cbbb8a  ("block: create the request_queue debugfs_dir on
registration") and so using the terminology on that commit, wouldn't
this not create now the root block debugfs dir for request-based block
drivers?

Hi Luis,

This patch should not change any behavior with CONFIG_DEBUG_FS=y.

Ignore CONFIG_DEBUG_FS=y. This is about blktrace which needs it for
both types of drivers.

As one can see in include/linux/debugfs.h, debugfs_create_dir() does not
create a directory with CONFIG_DEBUG_FS=n:

static inline struct dentry *debugfs_create_dir(const char *name,
						struct dentry *parent)
{
	return ERR_PTR(-ENODEV);
}

I think the only behavior change introduced by this patch is that
blk_debugfs_root remains NULL with CONFIG_DEBUG_FS=n instead of being set to
ERR_PTR(-ENODEV).

My point was commit 85e0cbbb8a made blk_debugfs_root non-null always now
when debugfs is enabled for both request-based block drivers and for
make_request block drivers (multiqueue). My reading is that with your
patch blk_debugfs_root will not be created for request-based block
drivers.

  Luis