linux-kernel - [PATCH 4.9 07/48] PM: wakeup: simplify the output logic of pm_show

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Date:   Mon,  7 Feb 2022 12:05:40 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Lee Jones <lee.jones@...aro.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
Subject: [PATCH 4.9 07/48] PM: wakeup: simplify the output logic of pm_show_wakelocks()

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

commit c9d967b2ce40d71e968eb839f36c936b8a9cf1ea upstream.

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.

Reviewed-by: Lee Jones <lee.jones@...aro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 kernel/power/wakelock.c |   12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

--- a/kernel/power/wakelock.c
+++ b/kernel/power/wakelock.c
@@ -38,23 +38,19 @@ ssize_t pm_show_wakelocks(char *buf, boo
 {
 	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