perf/core: Simplify the perf_mmap() control flow

Identity-transform:

	if (c) {
		X1;
	} else {
		Y;
		goto l;
	}

	X2;
  l:

into the simpler:

	if (c) {
		X1;
		X2;
	} else {
		Y;
	}

[ mingo: Forward ported it ]

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Ravi Bangoria <ravi.bangoria@amd.com>
Link: https://lore.kernel.org/r/20241104135519.095904637@infradead.org

diff --git a/kernel/events/core.c b/kernel/events/core.c
index ab4e497087daf3b6d99e2423d73e023e6c40bcaf..d1b04c8508810d86f5f79261b60dec68389c82e5 100644 (file)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -6701,6 +6701,42 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
 
        if (vma->vm_pgoff == 0) {
                nr_pages = (vma_size / PAGE_SIZE) - 1;
+
+               /*
+                * If we have rb pages ensure they're a power-of-two number, so we
+                * can do bitmasks instead of modulo.
+                */
+               if (nr_pages != 0 && !is_power_of_2(nr_pages))
+                       return -EINVAL;
+
+               if (vma_size != PAGE_SIZE * (1 + nr_pages))
+                       return -EINVAL;
+
+               WARN_ON_ONCE(event->ctx->parent_ctx);
+again:
+               mutex_lock(&event->mmap_mutex);
+               if (event->rb) {
+                       if (data_page_nr(event->rb) != nr_pages) {
+                               ret = -EINVAL;
+                               goto unlock;
+                       }
+
+                       if (!atomic_inc_not_zero(&event->rb->mmap_count)) {
+                               /*
+                                * Raced against perf_mmap_close(); remove the
+                                * event and try again.
+                                */
+                               ring_buffer_attach(event, NULL);
+                               mutex_unlock(&event->mmap_mutex);
+                               goto again;
+                       }
+
+                       /* We need the rb to map pages. */
+                       rb = event->rb;
+                       goto unlock;
+               }
+
+               user_extra = nr_pages + 1;
        } else {
                /*
                 * AUX area mapping: if rb->aux_nr_pages != 0, it's already
@@ -6760,47 +6796,8 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
 
                atomic_set(&rb->aux_mmap_count, 1);
                user_extra = nr_pages;
-
-               goto accounting;
-       }
-
-       /*
-        * If we have rb pages ensure they're a power-of-two number, so we
-        * can do bitmasks instead of modulo.
-        */
-       if (nr_pages != 0 && !is_power_of_2(nr_pages))
-               return -EINVAL;
-
-       if (vma_size != PAGE_SIZE * (1 + nr_pages))
-               return -EINVAL;
-
-       WARN_ON_ONCE(event->ctx->parent_ctx);
-again:
-       mutex_lock(&event->mmap_mutex);
-       if (event->rb) {
-               if (data_page_nr(event->rb) != nr_pages) {
-                       ret = -EINVAL;
-                       goto unlock;
-               }
-
-               if (!atomic_inc_not_zero(&event->rb->mmap_count)) {
-                       /*
-                        * Raced against perf_mmap_close(); remove the
-                        * event and try again.
-                        */
-                       ring_buffer_attach(event, NULL);
-                       mutex_unlock(&event->mmap_mutex);
-                       goto again;
-               }
-
-               /* We need the rb to map pages. */
-               rb = event->rb;
-               goto unlock;
        }
 
-       user_extra = nr_pages + 1;
-
-accounting:
        user_lock_limit = sysctl_perf_event_mlock >> (PAGE_SHIFT - 10);
 
        /*