linux-kernel - [PATCH AUTOSEL 5.10 20/25] PM: wakeup: simplify the output logic of pm_show

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Date:   Thu,  3 Feb 2022 15:34:41 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Lee Jones <lee.jones@...aro.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Sasha Levin <sashal@...nel.org>, rafael@...nel.org,
        pavel@....cz, len.brown@...el.com, linux-pm@...r.kernel.org
Subject: [PATCH AUTOSEL 5.10 20/25] PM: wakeup: simplify the output logic of pm_show_wakelocks()

From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

[ Upstream commit c9d967b2ce40d71e968eb839f36c936b8a9cf1ea ]

The buffer handling in pm_show_wakelocks() is tricky, and hopefully
correct.  Ensure it really is correct by using sysfs_emit_at() which
handles all of the tricky string handling logic in a PAGE_SIZE buffer
for us automatically as this is a sysfs file being read from.

Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Reviewed-by: Lee Jones <lee.jones@...aro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 kernel/power/wakelock.c | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/kernel/power/wakelock.c b/kernel/power/wakelock.c
index 105df4dfc7839..52571dcad768b 100644
--- a/kernel/power/wakelock.c
+++ b/kernel/power/wakelock.c
@@ -39,23 +39,20 @@ ssize_t pm_show_wakelocks(char *buf, bool show_active)
 {
 	struct rb_node *node;
 	struct wakelock *wl;
-	char *str = buf;
-	char *end = buf + PAGE_SIZE;
+	int len = 0;
 
 	mutex_lock(&wakelocks_lock);
 
 	for (node = rb_first(&wakelocks_tree); node; node = rb_next(node)) {
 		wl = rb_entry(node, struct wakelock, node);
 		if (wl->ws->active == show_active)
-			str += scnprintf(str, end - str, "%s ", wl->name);
+			len += sysfs_emit_at(buf, len, "%s ", wl->name);
 	}
-	if (str > buf)
-		str--;
 
-	str += scnprintf(str, end - str, "\n");
+	len += sysfs_emit_at(buf, len, "\n");
 
 	mutex_unlock(&wakelocks_lock);
-	return (str - buf);
+	return len;
 }
 
 #if CONFIG_PM_WAKELOCKS_LIMIT > 0
-- 
2.34.1