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UPSTREAM: mm/damon/dbgfs: export kdamond pid to the user space

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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.

Link: https://lkml.kernel.org/r/20210716081449.22187-9-sj38.park@gmail.com
Signed-off-by: SeongJae Park <sjpark@amazon.de>
Reviewed-by: Fernand Sieber <sieberf@amazon.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Amit Shah <amit@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Brendan Higgins <brendanhiggins@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: David Woodhouse <dwmw@amazon.com>
Cc: Fan Du <fan.du@intel.com>
Cc: Greg Kroah-Hartman <greg@kroah.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Joe Perches <joe@perches.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Leonard Foerster <foersleo@amazon.de>
Cc: Marco Elver <elver@google.com>
Cc: Markus Boehme <markubo@amazon.de>
Cc: Maximilian Heyne <mheyne@amazon.de>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

(cherry picked from commit 429538e85410c3ae12719ec42b89ab873ed6d47b)

Bug: 228223814
Signed-off-by: Hailong Tu <tuhailong@oppo.com>
Change-Id: I32d41776a1850ed189b2759194061004ca8a83cf
This commit is contained in:
SeongJae Park 2021-09-07 19:56:57 -07:00 committed by Hailong Tu
parent c10dc7808e
commit 562b676ce9
1 changed files with 35 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

37
mm/damon/dbgfs.c
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@ -239,6 +239,32 @@ 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;
@ -258,10 +284,17 @@ 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++)