From nobody Sun Oct 5 00:07:11 2025 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 38C7E2EBDD5 for ; Tue, 12 Aug 2025 10:46:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754995576; cv=none; b=kVi3vimJmUNTeCy2MVXlqo9QVfaEnwHLlvM3llxI7uuslnKANsWBvKl1j3T+PFeOYMenhKLVW5iuVhxlmxHfpVdgfgZ6e6NyTup2i6fyk3UpR0ltg+BoYkbKBA0VzfJmFNAQTaTA83T2gkfWp+RkdtpNo5oyMHbs0CL4dyZEmfE= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754995576; c=relaxed/simple; bh=zsUoYfmrwBZufVYd2oSJFDKq0MGsmEWxFkUupdw1aGI=; h=Message-ID:Date:From:To:Cc:Subject:References:MIME-Version: Content-Type; b=lMN2Q0Ry6YG/uTZvgb9lDFjucIh7S1y3lwVp6H/G/Og9ePMFohuGBJVIcjqNO0JVNatSGQOBQNyYBOb1j+JNEH8yNkyDxmULNiJIEALSdyf09Mg+7ixidwkZWWKH+8JLxgSAYX4s8HR5brVvMxKgocn5jcPYCprUoPhA1ZSfxRw= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=jidkELdJ; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="jidkELdJ" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=Content-Type:MIME-Version:References: Subject:Cc:To:From:Date:Message-ID:Sender:Reply-To:Content-Transfer-Encoding: Content-ID:Content-Description:In-Reply-To; bh=vH3yePd5DKCVSO1Y/zfCgO448JmB78RevnyS2SQs/eI=; b=jidkELdJqhmcWelCr6GAeNRiln KoG1RQHgfe9N3+rujY9rU0s+6UrY5BHueu5MYqJtZyWenhNvA0eo/AzckxcjcE5ALqBgeZrQqJpxN mcc8FQGZ/tMiVJp/yrvEvXCHeCecBO7oYdwwBeyoFhRVL7bAfqOEP2ZQLuhwxXO1/9wjcElhQLSCJ jOVjF9A/4ggMm33cZNxM7mJOFfer1PbdDOHHgzt3DZogkcqGIinG62G/6NwwrvPP0clhwAQsD+6oW 9Vfde9OVXAj0ko0Xhc4cwTFn2YdDtjo3afSnSetMbVNn4y88bXD7Sp82UTN+aNPDEK0OHPL4ES4RO YQ1SYtgw==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.98.2 #2 (Red Hat Linux)) id 1ulmWB-0000000FmkA-21YP; Tue, 12 Aug 2025 10:46:11 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 0) id BB4F9302E5F; Tue, 12 Aug 2025 12:46:09 +0200 (CEST) Message-ID: <20250812104019.722214699@infradead.org> User-Agent: quilt/0.68 Date: Tue, 12 Aug 2025 12:39:10 +0200 From: Peter Zijlstra To: tglx@linutronix.de Cc: linux-kernel@vger.kernel.org, peterz@infradead.org, torvalds@linuxfoundation.org, mingo@kernel.org, namhyung@kernel.org, acme@redhat.com, kees@kernel.org Subject: [PATCH v3 12/15] perf: Split out the RB allocation References: <20250812103858.234850285@infradead.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Move the RB buffer allocation branch into its own function. Originally-by: Thomas Gleixner Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Lorenzo Stoakes --- kernel/events/core.c | 145 +++++++++++++++++++++++++---------------------= ----- 1 file changed, 73 insertions(+), 72 deletions(-) --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -6970,6 +6970,75 @@ static void perf_mmap_account(struct vm_ atomic64_add(extra, &vma->vm_mm->pinned_vm); } =20 +static int perf_mmap_rb(struct vm_area_struct *vma, struct perf_event *eve= nt, + unsigned long nr_pages) +{ + long extra =3D 0, user_extra =3D nr_pages; + struct perf_buffer *rb; + int rb_flags =3D 0; + + nr_pages -=3D 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 !=3D 0 && !is_power_of_2(nr_pages)) + return -EINVAL; + + WARN_ON_ONCE(event->ctx->parent_ctx); + + if (event->rb) { + if (data_page_nr(event->rb) !=3D nr_pages) + return -EINVAL; + + if (atomic_inc_not_zero(&event->rb->mmap_count)) { + /* + * Success -- managed to mmap() the same buffer + * multiple times. + */ + perf_mmap_account(vma, user_extra, extra); + atomic_inc(&event->mmap_count); + return 0; + } + + /* + * Raced against perf_mmap_close()'s + * atomic_dec_and_mutex_lock() remove the + * event and continue as if !event->rb + */ + ring_buffer_attach(event, NULL); + } + + if (!perf_mmap_calc_limits(vma, &user_extra, &extra)) + return -EPERM; + + if (vma->vm_flags & VM_WRITE) + rb_flags |=3D RING_BUFFER_WRITABLE; + + rb =3D rb_alloc(nr_pages, + event->attr.watermark ? event->attr.wakeup_watermark : 0, + event->cpu, rb_flags); + + if (!rb) + return -ENOMEM; + + atomic_set(&rb->mmap_count, 1); + rb->mmap_user =3D get_current_user(); + rb->mmap_locked =3D extra; + + ring_buffer_attach(event, rb); + + perf_event_update_time(event); + perf_event_init_userpage(event); + perf_event_update_userpage(event); + + perf_mmap_account(vma, user_extra, extra); + atomic_inc(&event->mmap_count); + + return 0; +} + static int perf_mmap_aux(struct vm_area_struct *vma, struct perf_event *ev= ent, unsigned long nr_pages) { @@ -7050,10 +7119,8 @@ static int perf_mmap(struct file *file, { struct perf_event *event =3D file->private_data; unsigned long vma_size, nr_pages; - long user_extra =3D 0, extra =3D 0; - struct perf_buffer *rb =3D NULL; - int ret, flags =3D 0; mapped_f mapped; + int ret; =20 /* * Don't allow mmap() of inherited per-task counters. This would @@ -7079,8 +7146,6 @@ static int perf_mmap(struct file *file, if (vma_size !=3D PAGE_SIZE * nr_pages) return -EINVAL; =20 - user_extra =3D nr_pages; - mutex_lock(&event->mmap_mutex); ret =3D -EINVAL; =20 @@ -7094,74 +7159,10 @@ static int perf_mmap(struct file *file, goto unlock; } =20 - if (vma->vm_pgoff =3D=3D 0) { - nr_pages -=3D 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 !=3D 0 && !is_power_of_2(nr_pages)) - goto unlock; - - WARN_ON_ONCE(event->ctx->parent_ctx); - - if (event->rb) { - if (data_page_nr(event->rb) !=3D nr_pages) - goto unlock; - - if (atomic_inc_not_zero(&event->rb->mmap_count)) { - /* - * Success -- managed to mmap() the same buffer - * multiple times. - */ - ret =3D 0; - perf_mmap_account(vma, user_extra, extra); - atomic_inc(&event->mmap_count); - goto unlock; - } - - /* - * Raced against perf_mmap_close()'s - * atomic_dec_and_mutex_lock() remove the - * event and continue as if !event->rb - */ - ring_buffer_attach(event, NULL); - } - - if (!perf_mmap_calc_limits(vma, &user_extra, &extra)) { - ret =3D -EPERM; - goto unlock; - } - - if (vma->vm_flags & VM_WRITE) - flags |=3D RING_BUFFER_WRITABLE; - - rb =3D rb_alloc(nr_pages, - event->attr.watermark ? event->attr.wakeup_watermark : 0, - event->cpu, flags); - - if (!rb) { - ret =3D -ENOMEM; - goto unlock; - } - - atomic_set(&rb->mmap_count, 1); - rb->mmap_user =3D get_current_user(); - rb->mmap_locked =3D extra; - - ring_buffer_attach(event, rb); - - perf_event_update_time(event); - perf_event_init_userpage(event); - perf_event_update_userpage(event); - ret =3D 0; - - perf_mmap_account(vma, user_extra, extra); - atomic_inc(&event->mmap_count); - } else { + if (vma->vm_pgoff =3D=3D 0) + ret =3D perf_mmap_rb(vma, event, nr_pages); + else ret =3D perf_mmap_aux(vma, event, nr_pages); - } =20 unlock: mutex_unlock(&event->mmap_mutex);