[tip: perf/core] perf: Make RB allocation branch self sufficient

[tip-bot2 for Peter Zijlstra]

The following commit has been merged into the perf/core branch of tip:

Commit-ID:     191759e5ea9f6995171ed2ffcc41a2377f946a3a
Gitweb:        https://git.kernel.org/tip/191759e5ea9f6995171ed2ffcc41a2377f946a3a
Author:        Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate:    Tue, 12 Aug 2025 12:39:09 +02:00
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Fri, 15 Aug 2025 13:13:01 +02:00

perf: Make RB allocation branch self sufficient

Ensure @rb usage doesn't extend out of the branch block.

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20250812104019.605285302@xxxxxxxxxxxxx
---
 kernel/events/core.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index e76afd9..875c27b 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -7116,8 +7116,6 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
 				 * multiple times.
 				 */
 				ret = 0;
-				/* We need the rb to map pages. */
-				rb = event->rb;
 				perf_mmap_account(vma, user_extra, extra);
 				atomic_inc(&event->mmap_count);
 				goto unlock;
@@ -7136,8 +7134,6 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
 			goto unlock;
 		}
 
-		WARN_ON(!rb && event->rb);
-
 		if (vma->vm_flags & VM_WRITE)
 			flags |= RING_BUFFER_WRITABLE;
 
@@ -7190,7 +7186,7 @@ unlock:
 	 * full cleanup in this case and therefore does not invoke
 	 * vmops::close().
 	 */
-	ret = map_range(rb, vma);
+	ret = map_range(event->rb, vma);
 	if (ret)
 		perf_mmap_close(vma);