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Subject[PATCH V4 2/2] mm/damon/dbgfs: Add adaptive_targets list check before enable monitor_on
Date
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.

Signed-off-by: Xin Hao <xhao@linux.alibaba.com>
---
include/linux/damon.h | 1 +
mm/damon/core.c | 5 +++++
mm/damon/dbgfs.c | 15 ++++++++++++---
3 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index 715dadd21f7c..4fce5f1f6dad 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -316,6 +316,7 @@ 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);
diff --git a/mm/damon/core.c b/mm/damon/core.c
index 2f6785737902..c3a1374dbe0b 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -156,6 +156,11 @@ 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);
diff --git a/mm/damon/dbgfs.c b/mm/damon/dbgfs.c
index c90988a20fa4..a02cf6bee8e8 100644
--- a/mm/damon/dbgfs.c
+++ b/mm/damon/dbgfs.c
@@ -861,12 +861,21 @@ 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;
--
2.31.0
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