linux-kernel - [PATCH v3 04/15] perf: Move perf_mmap_calc_limits() into both rb and aux branches

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Message-ID: <20250812104018.781244099@infradead.org>
Date: Tue, 12 Aug 2025 12:39:02 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: tglx@...utronix.de
Cc: linux-kernel@...r.kernel.org,
 peterz@...radead.org,
 torvalds@...uxfoundation.org,
 mingo@...nel.org,
 namhyung@...nel.org,
 acme@...hat.com,
 kees@...nel.org
Subject: [PATCH v3 04/15] perf: Move perf_mmap_calc_limits() into both rb and aux branches

  if (cond) {
    A;
  } else {
    B;
  }
  C;

into

  if (cond) {
    A;
    C;
  } else {
    B;
    C;
  }

Suggested-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 kernel/events/core.c |   26 ++++++++++++++++++--------
 1 file changed, 18 insertions(+), 8 deletions(-)

--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -7054,6 +7054,16 @@ static int perf_mmap(struct file *file,
 			ring_buffer_attach(event, NULL);
 		}
 
+		if (!perf_mmap_calc_limits(vma, &user_extra, &extra)) {
+			ret = -EPERM;
+			goto unlock;
+		}
+
+		WARN_ON(!rb && event->rb);
+
+		if (vma->vm_flags & VM_WRITE)
+			flags |= RING_BUFFER_WRITABLE;
+
 	} else {
 		/*
 		 * AUX area mapping: if rb->aux_nr_pages != 0, it's already
@@ -7100,17 +7110,17 @@ static int perf_mmap(struct file *file,
 			ret = 0;
 			goto unlock;
 		}
-	}
 
-	if (!perf_mmap_calc_limits(vma, &user_extra, &extra)) {
-		ret = -EPERM;
-		goto unlock;
-	}
+		if (!perf_mmap_calc_limits(vma, &user_extra, &extra)) {
+			ret = -EPERM;
+			goto unlock;
+		}
 
-	WARN_ON(!rb && event->rb);
+		WARN_ON(!rb && event->rb);
 
-	if (vma->vm_flags & VM_WRITE)
-		flags |= RING_BUFFER_WRITABLE;
+		if (vma->vm_flags & VM_WRITE)
+			flags |= RING_BUFFER_WRITABLE;
+	}
 
 	if (!rb) {
 		rb = rb_alloc(nr_pages,