+ ref_tracker-have-callers-pass-output-function-to-pr_ostream.patch added to mm-nonmm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

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The patch titled
     Subject: ref_tracker: have callers pass output function to pr_ostream()
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     ref_tracker-have-callers-pass-output-function-to-pr_ostream.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/ref_tracker-have-callers-pass-output-function-to-pr_ostream.patch

This patch will later appear in the mm-nonmm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Jeff Layton <jlayton@kernel.org>
Subject: ref_tracker: have callers pass output function to pr_ostream()
Date: Tue, 03 Jun 2025 07:27:14 -0400

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.

Link: https://lkml.kernel.org/r/20250603-reftrack-dbgfs-v13-3-7b2a425019d8@kernel.org
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Cc: Dave Airlie <airlied@gmail.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Eric Dumaze <edumazet@google.com>
Cc: Jakub Kacinski <kuba@kernel.org>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Jonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Krzysztof Karas <krzysztof.karas@intel.com>
Cc: Kuniyuki Iwashima <kuniyu@amazon.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Qasim Ijaz <qasdev00@gmail.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Simon Horman <horms@kernel.org>
Cc: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Cc: Thomas Zimemrmann <tzimmermann@suse.de>
Cc: Tvrtko Ursulin <tursulin@ursulin.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/ref_tracker.h |    2 +
 lib/ref_tracker.c           |   52 ++++++++++++++++++++++++----------
 2 files changed, 39 insertions(+), 15 deletions(-)

--- a/include/linux/ref_tracker.h~ref_tracker-have-callers-pass-output-function-to-pr_ostream
+++ a/include/linux/ref_tracker.h
@@ -6,6 +6,8 @@
 #include <linux/spinlock.h>
 #include <linux/stackdepot.h>
 
+#define __ostream_printf __printf(2, 3)
+
 struct ref_tracker;
 
 struct ref_tracker_dir {
--- a/lib/ref_tracker.c~ref_tracker-have-callers-pass-output-function-to-pr_ostream
+++ a/lib/ref_tracker.c
@@ -63,21 +63,38 @@ ref_tracker_get_stats(struct ref_tracker
 }
 
 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);
+	if (ret > 0)
+		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
@@ -96,8 +113,8 @@ __ref_tracker_dir_pr_ostream(struct ref_
 
 	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;
 	}
 
@@ -107,14 +124,15 @@ __ref_tracker_dir_pr_ostream(struct ref_
 		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);
 
@@ -124,7 +142,8 @@ __ref_tracker_dir_pr_ostream(struct ref_
 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);
 }
@@ -143,7 +162,10 @@ 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);
_

Patches currently in -mm which might be from jlayton@kernel.org are

ref_tracker-dont-use-%pk-in-pr_ostream-output.patch
ref_tracker-add-a-top-level-debugfs-directory-for-ref_tracker.patch
ref_tracker-have-callers-pass-output-function-to-pr_ostream.patch
ref_tracker-add-a-static-classname-string-to-each-ref_tracker_dir.patch
ref_tracker-allow-pr_ostream-to-print-directly-to-a-seq_file.patch
ref_tracker-automatically-register-a-file-in-debugfs-for-a-ref_tracker_dir.patch
ref_tracker-add-a-way-to-create-a-symlink-to-the-ref_tracker_dir-debugfs-file.patch
net-add-symlinks-to-ref_tracker_dir-for-netns.patch
ref_tracker-eliminate-the-ref_tracker_dir-name-field.patch