linux-kernel - [PATCH v2 3/8] ref_tracker: have callers pass output function to pr

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Message-Id: <20250415-reftrack-dbgfs-v2-3-b18c4abd122f@kernel.org>
Date: Tue, 15 Apr 2025 14:49:41 -0400
From: Jeff Layton <jlayton@...nel.org>
To: Andrew Morton <akpm@...ux-foundation.org>, 
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
 Simon Horman <horms@...nel.org>
Cc: Kuniyuki Iwashima <kuniyu@...zon.com>, Qasim Ijaz <qasdev00@...il.com>, 
 Nathan Chancellor <nathan@...nel.org>, Andrew Lunn <andrew@...n.ch>, 
 linux-kernel@...r.kernel.org, netdev@...r.kernel.org, 
 Jeff Layton <jlayton@...nel.org>
Subject: [PATCH v2 3/8] ref_tracker: have callers pass output function to
 pr_ostream()

In a later patch, we'll be adding a 3rd mechanism for outputting
ref_tracker info via seq_file. Instead of a conditional, have the caller
set a pointer to an output function in struct ostream. As part of this,
the log prefix must be explicitly passed in, as it's too late for the
pr_fmt macro.

Signed-off-by: Jeff Layton <jlayton@...nel.org>
---
 lib/ref_tracker.c | 53 ++++++++++++++++++++++++++++++++++++++---------------
 1 file changed, 38 insertions(+), 15 deletions(-)

diff --git a/lib/ref_tracker.c b/lib/ref_tracker.c
index a66cde325920780cfe7529ea9d827d0ee943318d..b6e0a87dd75eddef4d504419c0cf398ea65c19d8 100644
--- a/lib/ref_tracker.c
+++ b/lib/ref_tracker.c
@@ -64,22 +64,40 @@ ref_tracker_get_stats(struct ref_tracker_dir *dir, unsigned int limit)
 	return stats;
 }
 
+#define __ostream_printf __printf(2, 3)
+
 struct ostream {
+	void __ostream_printf (*func)(struct ostream *stream, char *fmt, ...);
+	char *prefix;
 	char *buf;
 	int size, used;
 };
 
+static void __ostream_printf pr_ostream_log(struct ostream *stream, char *fmt, ...)
+{
+	va_list args;
+
+	va_start(args, fmt);
+	vprintk(fmt, args);
+	va_end(args);
+}
+
+static void __ostream_printf pr_ostream_buf(struct ostream *stream, char *fmt, ...)
+{
+	int ret, len = stream->size - stream->used;
+	va_list args;
+
+	va_start(args, fmt);
+	ret = vsnprintf(stream->buf + stream->used, len, fmt, args);
+	va_end(args);
+	stream->used += min(ret, len);
+}
+
 #define pr_ostream(stream, fmt, args...) \
 ({ \
 	struct ostream *_s = (stream); \
 \
-	if (!_s->buf) { \
-		pr_err(fmt, ##args); \
-	} else { \
-		int ret, len = _s->size - _s->used; \
-		ret = snprintf(_s->buf + _s->used, len, pr_fmt(fmt), ##args); \
-		_s->used += min(ret, len); \
-	} \
+	_s->func(_s, fmt, ##args); \
 })
 
 static void
@@ -98,8 +116,8 @@ __ref_tracker_dir_pr_ostream(struct ref_tracker_dir *dir,
 
 	stats = ref_tracker_get_stats(dir, display_limit);
 	if (IS_ERR(stats)) {
-		pr_ostream(s, "%s@%p: couldn't get stats, error %pe\n",
-			   dir->name, dir, stats);
+		pr_ostream(s, "%s%s@%p: couldn't get stats, error %pe\n",
+			   s->prefix, dir->name, dir, stats);
 		return;
 	}
 
@@ -109,14 +127,15 @@ __ref_tracker_dir_pr_ostream(struct ref_tracker_dir *dir,
 		stack = stats->stacks[i].stack_handle;
 		if (sbuf && !stack_depot_snprint(stack, sbuf, STACK_BUF_SIZE, 4))
 			sbuf[0] = 0;
-		pr_ostream(s, "%s@%p has %d/%d users at\n%s\n", dir->name, dir,
-			   stats->stacks[i].count, stats->total, sbuf);
+		pr_ostream(s, "%s%s@%p has %d/%d users at\n%s\n", s->prefix,
+			   dir->name, dir, stats->stacks[i].count,
+			   stats->total, sbuf);
 		skipped -= stats->stacks[i].count;
 	}
 
 	if (skipped)
-		pr_ostream(s, "%s@%p skipped reports about %d/%d users.\n",
-			   dir->name, dir, skipped, stats->total);
+		pr_ostream(s, "%s%s@%p skipped reports about %d/%d users.\n",
+			   s->prefix, dir->name, dir, skipped, stats->total);
 
 	kfree(sbuf);
 
@@ -126,7 +145,8 @@ __ref_tracker_dir_pr_ostream(struct ref_tracker_dir *dir,
 void ref_tracker_dir_print_locked(struct ref_tracker_dir *dir,
 				  unsigned int display_limit)
 {
-	struct ostream os = {};
+	struct ostream os = { .func = pr_ostream_log,
+			      .prefix = "ref_tracker: " };
 
 	__ref_tracker_dir_pr_ostream(dir, display_limit, &os);
 }
@@ -145,7 +165,10 @@ EXPORT_SYMBOL(ref_tracker_dir_print);
 
 int ref_tracker_dir_snprint(struct ref_tracker_dir *dir, char *buf, size_t size)
 {
-	struct ostream os = { .buf = buf, .size = size };
+	struct ostream os = { .func = pr_ostream_buf,
+			      .prefix = "ref_tracker: ",
+			      .buf = buf,
+			      .size = size };
 	unsigned long flags;
 
 	spin_lock_irqsave(&dir->lock, flags);

-- 
2.49.0