Commit 95487837 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

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: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Reviewed-by: default avatarRavi Bangoria <ravi.bangoria@amd.com>
Link: https://lore.kernel.org/r/20241104135519.095904637@infradead.org
parent c5b96789

kernel/events/core.c

+36 −39
Original line number Diff line number Diff line
@@ -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);



	/*