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Message-ID: <20250812104019.494205648@infradead.org>
Date: Tue, 12 Aug 2025 12:39:08 +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 10/15] perf: Split out the AUX buffer allocation
Move the AUX buffer allocation branch into its own function.
Originally-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
kernel/events/core.c | 144 +++++++++++++++++++++++++++------------------------
1 file changed, 77 insertions(+), 67 deletions(-)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -6970,6 +6970,82 @@ static void perf_mmap_account(struct vm_
atomic64_add(extra, &vma->vm_mm->pinned_vm);
}
+static int perf_mmap_aux(struct vm_area_struct *vma, struct perf_event *event,
+ unsigned long nr_pages)
+{
+ long extra = 0, user_extra = nr_pages;
+ u64 aux_offset, aux_size;
+ struct perf_buffer *rb;
+ int ret, rb_flags = 0;
+
+ rb = event->rb;
+ if (!rb)
+ return -EINVAL;
+
+ guard(mutex)(&rb->aux_mutex);
+
+ /*
+ * AUX area mapping: if rb->aux_nr_pages != 0, it's already
+ * mapped, all subsequent mappings should have the same size
+ * and offset. Must be above the normal perf buffer.
+ */
+ aux_offset = READ_ONCE(rb->user_page->aux_offset);
+ aux_size = READ_ONCE(rb->user_page->aux_size);
+
+ if (aux_offset < perf_data_size(rb) + PAGE_SIZE)
+ return -EINVAL;
+
+ if (aux_offset != vma->vm_pgoff << PAGE_SHIFT)
+ return -EINVAL;
+
+ /* already mapped with a different offset */
+ if (rb_has_aux(rb) && rb->aux_pgoff != vma->vm_pgoff)
+ return -EINVAL;
+
+ if (aux_size != nr_pages * PAGE_SIZE)
+ return -EINVAL;
+
+ /* already mapped with a different size */
+ if (rb_has_aux(rb) && rb->aux_nr_pages != nr_pages)
+ return -EINVAL;
+
+ if (!is_power_of_2(nr_pages))
+ return -EINVAL;
+
+ if (!atomic_inc_not_zero(&rb->mmap_count))
+ return -EINVAL;
+
+ if (rb_has_aux(rb)) {
+ atomic_inc(&rb->aux_mmap_count);
+
+ } else {
+ if (!perf_mmap_calc_limits(vma, &user_extra, &extra)) {
+ atomic_dec(&rb->mmap_count);
+ return -EPERM;
+ }
+
+ WARN_ON(!rb && event->rb);
+
+ if (vma->vm_flags & VM_WRITE)
+ rb_flags |= RING_BUFFER_WRITABLE;
+
+ ret = rb_alloc_aux(rb, event, vma->vm_pgoff, nr_pages,
+ event->attr.aux_watermark, rb_flags);
+ if (ret) {
+ atomic_dec(&rb->mmap_count);
+ return ret;
+ }
+
+ atomic_set(&rb->aux_mmap_count, 1);
+ rb->aux_mmap_locked = extra;
+ }
+
+ perf_mmap_account(vma, user_extra, extra);
+ atomic_inc(&event->mmap_count);
+
+ return 0;
+}
+
static int perf_mmap(struct file *file, struct vm_area_struct *vma)
{
struct perf_event *event = file->private_data;
@@ -7087,73 +7163,7 @@ static int perf_mmap(struct file *file,
perf_mmap_account(vma, user_extra, extra);
atomic_inc(&event->mmap_count);
} else {
- /*
- * AUX area mapping: if rb->aux_nr_pages != 0, it's already
- * mapped, all subsequent mappings should have the same size
- * and offset. Must be above the normal perf buffer.
- */
- u64 aux_offset, aux_size;
-
- rb = event->rb;
- if (!rb)
- goto unlock;
-
- guard(mutex)(&rb->aux_mutex);
-
- aux_offset = READ_ONCE(rb->user_page->aux_offset);
- aux_size = READ_ONCE(rb->user_page->aux_size);
-
- if (aux_offset < perf_data_size(rb) + PAGE_SIZE)
- goto unlock;
-
- if (aux_offset != vma->vm_pgoff << PAGE_SHIFT)
- goto unlock;
-
- /* already mapped with a different offset */
- if (rb_has_aux(rb) && rb->aux_pgoff != vma->vm_pgoff)
- goto unlock;
-
- if (aux_size != nr_pages * PAGE_SIZE)
- goto unlock;
-
- /* already mapped with a different size */
- if (rb_has_aux(rb) && rb->aux_nr_pages != nr_pages)
- goto unlock;
-
- if (!is_power_of_2(nr_pages))
- goto unlock;
-
- if (!atomic_inc_not_zero(&rb->mmap_count))
- goto unlock;
-
- if (rb_has_aux(rb)) {
- atomic_inc(&rb->aux_mmap_count);
- ret = 0;
-
- } else {
- if (!perf_mmap_calc_limits(vma, &user_extra, &extra)) {
- ret = -EPERM;
- atomic_dec(&rb->mmap_count);
- goto unlock;
- }
-
- WARN_ON(!rb && event->rb);
-
- if (vma->vm_flags & VM_WRITE)
- flags |= RING_BUFFER_WRITABLE;
-
- ret = rb_alloc_aux(rb, event, vma->vm_pgoff, nr_pages,
- event->attr.aux_watermark, flags);
- if (ret) {
- atomic_dec(&rb->mmap_count);
- goto unlock;
- }
-
- atomic_set(&rb->aux_mmap_count, 1);
- rb->aux_mmap_locked = extra;
- }
- perf_mmap_account(vma, user_extra, extra);
- atomic_inc(&event->mmap_count);
+ ret = perf_mmap_aux(vma, event, nr_pages);
}
unlock:
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