From nobody Sun Feb 8 11:44:54 2026 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.16]) (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 CFA0117591; Sat, 13 Jul 2024 02:13:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.16 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720836803; cv=none; b=HlMFGVagxDNIw1K2R0GLeMcONdlkl6i3kuuqWu3ZnD46Ruz6kvInXiVt2ABwzj3TZK9fabwj8vaAU3+EiJNcfm6cmHGRG7a/ZYmbcrTlpNySMac42r2vkg6WZazTPFGTHyPTUN/0EucahfgvAm4Eu+lOKHNzrqeMjwJDq43uFEg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720836803; c=relaxed/simple; bh=vbUi5zKMqImT3C+nksSqGjIBCDKIitAH3vpPg8VR/+w=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Tzaxc6B/haPXc5u8Sc8cqm3cfU1zwHv88bj1MbksRuXGkXdvYEFK/vH8so7QJZy9OFS3d9DqxfEfMU21ZpkDtBRY8KpyNKsIxQ4hDaPp+46PBlaeGEv3Lx5FtCasiSCaAAV1W5qKSbbSu9aPRVKwTpttdkJNRWLX2skTmeYYj64= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=QAI3Fh5R; arc=none smtp.client-ip=192.198.163.16 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="QAI3Fh5R" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1720836801; x=1752372801; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=vbUi5zKMqImT3C+nksSqGjIBCDKIitAH3vpPg8VR/+w=; b=QAI3Fh5RKOMuFodzxY3Aug6gPo7SZJO3+PMxmqCmc05W//RkQB8qdwgE F9+Eg0USu/qOwwknBQvvBwf+XvuFQmJXqiolC/pxIDdIU0EPhxxrT1aD5 mk9Ar2QZruaHgQxIDgXpFB7MbLjJoPRPqQQkb6pUQiFtxcLmJz0Z1Csat QovvD/NlTkVZsFlgVGD8jqIt43UvoVkUPIYoFQM90BW5GZsBs/ZugnMuK HFK5974C4SWdAMBvfEPnPSE8xfJc5h2Fjf2iMpiqNy3kZLTq2eXyRjI23 +e1MDqkSlamM9tYljjvIW8DXxnvPXvaC8nC8J8ipWW1fXpkHuPegppdbd Q==; X-CSE-ConnectionGUID: R1B9IaOfTg6H90wwVMRtPw== X-CSE-MsgGUID: +qwlZq1ISLuutiEfHo5lQw== X-IronPort-AV: E=McAfee;i="6700,10204,11131"; a="12531269" X-IronPort-AV: E=Sophos;i="6.09,204,1716274800"; d="scan'208";a="12531269" Received: from fmviesa005.fm.intel.com ([10.60.135.145]) by fmvoesa110.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 Jul 2024 19:13:21 -0700 X-CSE-ConnectionGUID: vADG1FrCSluLzH3d1BXzFA== X-CSE-MsgGUID: WOQ7wzXJTy6laTIRgMJ1Cg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.09,204,1716274800"; d="scan'208";a="53449891" Received: from linux-pnp-server-16.sh.intel.com ([10.239.177.152]) by fmviesa005.fm.intel.com with ESMTP; 12 Jul 2024 19:13:19 -0700 From: Yu Ma To: viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz, mjguzik@gmail.com, edumazet@google.com Cc: yu.ma@intel.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, pan.deng@intel.com, tianyou.li@intel.com, tim.c.chen@intel.com, tim.c.chen@linux.intel.com Subject: [PATCH v4 1/3] fs/file.c: remove sanity_check and add likely/unlikely in alloc_fd() Date: Fri, 12 Jul 2024 22:39:15 -0400 Message-ID: <20240713023917.3967269-2-yu.ma@intel.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240713023917.3967269-1-yu.ma@intel.com> References: <20240614163416.728752-1-yu.ma@intel.com> <20240713023917.3967269-1-yu.ma@intel.com> 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" alloc_fd() has a sanity check inside to make sure the struct file mapping t= o the allocated fd is NULL. Remove this sanity check since it can be assured by exisitng zero initilization and NULL set when recycling fd. Meanwhile, add likely/unlikely and expand_file() call avoidance to reduce the work under file_lock. Reviewed-by: Tim Chen Signed-off-by: Yu Ma Reviewed-by: Jan Kara --- fs/file.c | 33 ++++++++++++++------------------- 1 file changed, 14 insertions(+), 19 deletions(-) diff --git a/fs/file.c b/fs/file.c index a3b72aa64f11..e1b9d6df7941 100644 --- a/fs/file.c +++ b/fs/file.c @@ -515,7 +515,7 @@ static int alloc_fd(unsigned start, unsigned end, unsig= ned flags) if (fd < files->next_fd) fd =3D files->next_fd; =20 - if (fd < fdt->max_fds) + if (likely(fd < fdt->max_fds)) fd =3D find_next_fd(fdt, fd); =20 /* @@ -523,19 +523,21 @@ static int alloc_fd(unsigned start, unsigned end, uns= igned flags) * will limit the total number of files that can be opened. */ error =3D -EMFILE; - if (fd >=3D end) + if (unlikely(fd >=3D end)) goto out; =20 - error =3D expand_files(files, fd); - if (error < 0) - goto out; + if (unlikely(fd >=3D fdt->max_fds)) { + error =3D expand_files(files, fd); + if (error < 0) + goto out; =20 - /* - * If we needed to expand the fs array we - * might have blocked - try again. - */ - if (error) - goto repeat; + /* + * If we needed to expand the fs array we + * might have blocked - try again. + */ + if (error) + goto repeat; + } =20 if (start <=3D files->next_fd) files->next_fd =3D fd + 1; @@ -546,13 +548,6 @@ static int alloc_fd(unsigned start, unsigned end, unsi= gned flags) else __clear_close_on_exec(fd, fdt); error =3D fd; -#if 1 - /* Sanity check */ - if (rcu_access_pointer(fdt->fd[fd]) !=3D NULL) { - printk(KERN_WARNING "alloc_fd: slot %d not NULL!\n", fd); - rcu_assign_pointer(fdt->fd[fd], NULL); - } -#endif =20 out: spin_unlock(&files->file_lock); @@ -618,7 +613,7 @@ void fd_install(unsigned int fd, struct file *file) rcu_read_unlock_sched(); spin_lock(&files->file_lock); fdt =3D files_fdtable(files); - BUG_ON(fdt->fd[fd] !=3D NULL); + WARN_ON(fdt->fd[fd] !=3D NULL); rcu_assign_pointer(fdt->fd[fd], file); spin_unlock(&files->file_lock); return; --=20 2.43.0