linux-kernel - [PATCH v34 08/13] mm/damon/dbgfs: Export kdamond pid to the user space

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Fri, 16 Jul 2021 08:14:44 +0000
From:   SeongJae Park <sj38.park@...il.com>
To:     akpm@...ux-foundation.org
Cc:     SeongJae Park <sjpark@...zon.de>, Jonathan.Cameron@...wei.com,
        acme@...nel.org, alexander.shishkin@...ux.intel.com,
        amit@...nel.org, benh@...nel.crashing.org,
        brendanhiggins@...gle.com, corbet@....net, david@...hat.com,
        dwmw@...zon.com, elver@...gle.com, fan.du@...el.com,
        foersleo@...zon.de, greg@...ah.com, gthelen@...gle.com,
        guoju.fgj@...baba-inc.com, jgowans@...zon.com, joe@...ches.com,
        mgorman@...e.de, mheyne@...zon.de, minchan@...nel.org,
        mingo@...hat.com, namhyung@...nel.org, peterz@...radead.org,
        riel@...riel.com, rientjes@...gle.com, rostedt@...dmis.org,
        rppt@...nel.org, shakeelb@...gle.com, shuah@...nel.org,
        sieberf@...zon.com, sj38.park@...il.com, snu@...le79.org,
        vbabka@...e.cz, vdavydov.dev@...il.com, zgf574564920@...il.com,
        linux-damon@...zon.com, linux-mm@...ck.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v34 08/13] mm/damon/dbgfs: Export kdamond pid to the user space

From: SeongJae Park <sjpark@...zon.de>

For CPU usage accounting, knowing pid of the monitoring thread could be
helpful.  For example, users could use cpuaccount cgroups with the pid.

This commit therefore exports the pid of currently running monitoring
thread to the user space via 'kdamond_pid' file in the debugfs
directory.

Signed-off-by: SeongJae Park <sjpark@...zon.de>
Reviewed-by: Fernand Sieber <sieberf@...zon.com>
---
 mm/damon/dbgfs.c | 37 +++++++++++++++++++++++++++++++++++--
 1 file changed, 35 insertions(+), 2 deletions(-)

diff --git a/mm/damon/dbgfs.c b/mm/damon/dbgfs.c
index 322f624710d7..bd9bc6ede40e 100644
--- a/mm/damon/dbgfs.c
+++ b/mm/damon/dbgfs.c
@@ -237,6 +237,32 @@ static ssize_t dbgfs_target_ids_write(struct file *file,
 	return ret;
 }
 
+static ssize_t dbgfs_kdamond_pid_read(struct file *file,
+		char __user *buf, size_t count, loff_t *ppos)
+{
+	struct damon_ctx *ctx = file->private_data;
+	char *kbuf;
+	ssize_t len;
+
+	kbuf = kmalloc(count, GFP_KERNEL);
+	if (!kbuf)
+		return -ENOMEM;
+
+	mutex_lock(&ctx->kdamond_lock);
+	if (ctx->kdamond)
+		len = scnprintf(kbuf, count, "%d\n", ctx->kdamond->pid);
+	else
+		len = scnprintf(kbuf, count, "none\n");
+	mutex_unlock(&ctx->kdamond_lock);
+	if (!len)
+		goto out;
+	len = simple_read_from_buffer(buf, count, ppos, kbuf, len);
+
+out:
+	kfree(kbuf);
+	return len;
+}
+
 static int damon_dbgfs_open(struct inode *inode, struct file *file)
 {
 	file->private_data = inode->i_private;
@@ -256,10 +282,17 @@ static const struct file_operations target_ids_fops = {
 	.write = dbgfs_target_ids_write,
 };
 
+static const struct file_operations kdamond_pid_fops = {
+	.open = damon_dbgfs_open,
+	.read = dbgfs_kdamond_pid_read,
+};
+
 static void dbgfs_fill_ctx_dir(struct dentry *dir, struct damon_ctx *ctx)
 {
-	const char * const file_names[] = {"attrs", "target_ids"};
-	const struct file_operations *fops[] = {&attrs_fops, &target_ids_fops};
+	const char * const file_names[] = {"attrs", "target_ids",
+		"kdamond_pid"};
+	const struct file_operations *fops[] = {&attrs_fops, &target_ids_fops,
+		&kdamond_pid_fops};
 	int i;
 
 	for (i = 0; i < ARRAY_SIZE(file_names); i++)
-- 
2.17.1