Commit b5ca3e83 authored by Xin Hao's avatar Xin Hao Committed by Linus Torvalds
Browse files

mm/damon/dbgfs: add adaptive_targets list check before enable monitor_on 

When the ctx->adaptive_targets list is empty, I did some test on
monitor_on interface like this.

    # cat /sys/kernel/debug/damon/target_ids
    #
    # echo on > /sys/kernel/debug/damon/monitor_on
    # damon: kdamond (5390) starts

Though the ctx->adaptive_targets list is empty, but the kthread_run
still be called, and the kdamond.x thread still be created, this is
meaningless.

So there adds a judgment in 'dbgfs_monitor_on_write', if the
ctx->adaptive_targets list is empty, return -EINVAL.

Link: https://lkml.kernel.org/r/0a60a6e8ec9d71989e0848a4dc3311996ca3b5d4.1634720326.git.xhao@linux.alibaba.com


Signed-off-by: default avatarXin Hao <xhao@linux.alibaba.com>
Reviewed-by: default avatarSeongJae Park <sj@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent a460a360

include/linux/damon.h

+1 −0
Original line number Diff line number Diff line
@@ -440,6 +440,7 @@ void damon_destroy_scheme(struct damos *s); 


struct damon_target *damon_new_target(unsigned long id);

void damon_add_target(struct damon_ctx *ctx, struct damon_target *t);

bool damon_targets_empty(struct damon_ctx *ctx);

void damon_free_target(struct damon_target *t);

void damon_destroy_target(struct damon_target *t);

unsigned int damon_nr_regions(struct damon_target *t);

mm/damon/core.c

+5 −0
Original line number Diff line number Diff line
@@ -180,6 +180,11 @@ void damon_add_target(struct damon_ctx *ctx, struct damon_target *t) 
	list_add_tail(&t->list, &ctx->adaptive_targets);

}



bool damon_targets_empty(struct damon_ctx *ctx)

{

	return list_empty(&ctx->adaptive_targets);

}



static void damon_del_target(struct damon_target *t)

{

	list_del(&t->list);

mm/damon/dbgfs.c

+12 −3
Original line number Diff line number Diff line
@@ -878,12 +878,21 @@ static ssize_t dbgfs_monitor_on_write(struct file *file, 
		return -EINVAL;

	}



	if (!strncmp(kbuf, "on", count))

	if (!strncmp(kbuf, "on", count)) {

		int i;



		for (i = 0; i < dbgfs_nr_ctxs; i++) {

			if (damon_targets_empty(dbgfs_ctxs[i])) {

				kfree(kbuf);

				return -EINVAL;

			}

		}

		ret = damon_start(dbgfs_ctxs, dbgfs_nr_ctxs);

	else if (!strncmp(kbuf, "off", count))

	} else if (!strncmp(kbuf, "off", count)) {

		ret = damon_stop(dbgfs_ctxs, dbgfs_nr_ctxs);

	else

	} else {

		ret = -EINVAL;

	}



	if (!ret)

		ret = count;