Commit 43df7676 authored by SeongJae Park's avatar SeongJae Park Committed by Andrew Morton
Browse files

mm/damon/core: introduce repeat mode damon_call() 

damon_call() can be useful for reading or writing DAMON internal data for
one time.  A common pattern of DAMON core usage from DAMON modules is
doing such reads and writes repeatedly, for example, to periodically
update the DAMOS stats.  To do that with damon_call(), callers should call
damon_call() repeatedly, with their own delay loop.  Each caller doing
that is repetitive.  Introduce a repeat mode damon_call().  Callers can
use the mode by setting a new field in damon_call_control.  If the mode is
turned on, damon_call() returns success immediately, and DAMON repeats
invoking the callback function inside the kdamond main loop.

Link: https://lkml.kernel.org/r/20250712195016.151108-3-sj@kernel.org


Signed-off-by: default avatarSeongJae Park <sj@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 004ded6b

include/linux/damon.h

+2 −0
Original line number Diff line number Diff line
@@ -659,6 +659,7 @@ struct damon_callback { 
 *

 * @fn:			Function to be called back.

 * @data:		Data that will be passed to @fn.

 * @repeat:		Repeat invocations.

 * @return_code:	Return code from @fn invocation.

 *

 * Control damon_call(), which requests specific kdamond to invoke a given
@@ -667,6 +668,7 @@ struct damon_callback { 
struct damon_call_control {

	int (*fn)(void *data);

	void *data;

	bool repeat;

	int return_code;

/* private: internal use only */

	/* informs if the kdamond finished handling of the request */

mm/damon/core.c

+20 −5
Original line number Diff line number Diff line
@@ -1379,8 +1379,9 @@ bool damon_is_running(struct damon_ctx *ctx) 
 *

 * Ask DAMON worker thread (kdamond) of @ctx to call a function with an

 * argument data that respectively passed via &damon_call_control->fn and

 * &damon_call_control->data of @control, and wait until the kdamond finishes

 * handling of the request.

 * &damon_call_control->data of @control.  If &damon_call_control->repeat of

 * @control is set, further wait until the kdamond finishes handling of the

 * request.  Otherwise, return as soon as the request is made.

 *

 * The kdamond executes the function with the argument in the main loop, just

 * after a sampling of the iteration is finished.  The function can hence
@@ -1392,6 +1393,7 @@ bool damon_is_running(struct damon_ctx *ctx) 
 */

int damon_call(struct damon_ctx *ctx, struct damon_call_control *control)

{

	if (!control->repeat)

		init_completion(&control->completion);

	control->canceled = false;

	INIT_LIST_HEAD(&control->list);
@@ -1401,6 +1403,8 @@ int damon_call(struct damon_ctx *ctx, struct damon_call_control *control) 
	mutex_unlock(&ctx->call_controls_lock);

	if (!damon_is_running(ctx))

		return -EINVAL;

	if (control->repeat)

		return 0;

	wait_for_completion(&control->completion);

	if (control->canceled)

		return -ECANCELED;
@@ -2429,6 +2433,7 @@ static void kdamond_usleep(unsigned long usecs) 
static void kdamond_call(struct damon_ctx *ctx, bool cancel)

{

	struct damon_call_control *control;

	LIST_HEAD(repeat_controls);

	int ret = 0;



	while (true) {
@@ -2437,7 +2442,7 @@ static void kdamond_call(struct damon_ctx *ctx, bool cancel) 
				struct damon_call_control, list);

		mutex_unlock(&ctx->call_controls_lock);

		if (!control)

			return;

			break;

		if (cancel) {

			control->canceled = true;

		} else {
@@ -2447,8 +2452,18 @@ static void kdamond_call(struct damon_ctx *ctx, bool cancel) 
		mutex_lock(&ctx->call_controls_lock);

		list_del(&control->list);

		mutex_unlock(&ctx->call_controls_lock);

		if (!control->repeat)

			complete(&control->completion);

		else

			list_add(&control->list, &repeat_controls);

	}

	control = list_first_entry_or_null(&repeat_controls,

			struct damon_call_control, list);

	if (!control || cancel)

		return;

	mutex_lock(&ctx->call_controls_lock);

	list_add_tail(&control->list, &ctx->call_controls);

	mutex_unlock(&ctx->call_controls_lock);

}



/* Returns negative error code if it's not activated but should return */