From nobody Fri Feb 13 09:29:27 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5D779E7E652 for ; Wed, 27 Sep 2023 04:17:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229693AbjI0ER3 (ORCPT ); Wed, 27 Sep 2023 00:17:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41630 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229543AbjI0EQV (ORCPT ); Wed, 27 Sep 2023 00:16:21 -0400 Received: from mail-pl1-x62c.google.com (mail-pl1-x62c.google.com [IPv6:2607:f8b0:4864:20::62c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 799365245; Tue, 26 Sep 2023 17:16:35 -0700 (PDT) Received: by mail-pl1-x62c.google.com with SMTP id d9443c01a7336-1c47309a8ccso81804735ad.1; Tue, 26 Sep 2023 17:16:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1695773795; x=1696378595; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=HNJwTTZACq9yLQWS8t+PsblAtdyQNZRiQBfSWneDTAI=; b=HOyYLZvZsgGR7Yhfk2SJTVilR1RVXrnU0UrAnyOi6tmSaWCsv0I3m6YiW0uxBkPCUW gnzR4iDuK+vuTflEjZtpRpJyrCQZqkhtD5IIPP+6apTQwiyj79REQjq/U0baFiyoIyOG 8mkUBOht6cqvxtTFaZUH3uDKQ2Qq64OU8NGd4IrMWXrE4JrgwJIvV/rgZXq4RsTvt6hl oKmjJDRBtVenNaXffQJ44XQBebex7pnbwfeP+VKXvHkTQ/og/IEBNnDWHc1l0cPKaHkd 7DTwpgZIxm05ByD/nILLwjSzIaITsKmwJAnpyQCP9OfBGRcPgDQvkrW78Eh1SYLEH1y2 EnQA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1695773795; x=1696378595; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=HNJwTTZACq9yLQWS8t+PsblAtdyQNZRiQBfSWneDTAI=; b=CwwxR7t29v3HCP/awQUmXFiMx7CU9KpzOZXDfspGTHUNkkk6fR2Yw4DFI8sg7xD894 Im37PH2zVU9k4WahGoKteozhQMj20ubm3onVV/Iqe7mxSIF01BrXzYEJJXkEv3H5zolk R47q8pS+k6gzCVyPLw9MPHwV0d0sqtB0pfhr9DsfswH++fYO6LMku7KnUa1d5ngeJ8BO 3Pg1z1bSZEdtW8htX57Tr5Hu1FJqnmR7ST5K6jM9oH3S9hln+BSqRkta+A7B6n/9PEJm zNIt5jAtFJ0IHcfIVQrnYE0KAjETUjo8TW7UPehqxRwhnyZBn/uG0prg/TQf7ZUvcEnF YxYg== X-Gm-Message-State: AOJu0Ywyt9DJXRAbIdj6GGQw+4U18lk//Kc2AfimotQeVbFbaCjA00HK mBFz6ZEqwi6kmi1Myfrkswyw/NBs0o4= X-Google-Smtp-Source: AGHT+IGEoQ7+A0JA5z0kXlfyTZItPmnp0nZi0UEkm75KmkCl9l0iN9IZ6VcHDazRrrnAKZjflc6YYw== X-Received: by 2002:a17:902:d2c7:b0:1b7:f64b:379b with SMTP id n7-20020a170902d2c700b001b7f64b379bmr758925plc.17.1695773794758; Tue, 26 Sep 2023 17:16:34 -0700 (PDT) Received: from wheely.local0.net ([203.63.110.121]) by smtp.gmail.com with ESMTPSA id n5-20020a170902e54500b001b8c6890623sm11703754plf.7.2023.09.26.17.16.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 26 Sep 2023 17:16:34 -0700 (PDT) From: Nicholas Piggin To: linux-nfs@vger.kernel.org Cc: Nicholas Piggin , Trond Myklebust , Anna Schumaker , linux-kernel@vger.kernel.org Subject: [RFC PATCH] nfs: reduce stack usage of nfs_get_root Date: Wed, 27 Sep 2023 10:16:23 +1000 Message-Id: <20230927001624.750031-1-npiggin@gmail.com> X-Mailer: git-send-email 2.40.1 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Move fsinfo allocation off stack, reducing stack overhead of nfs_get_root from 304 to 192 bytes. Signed-off-by: Nicholas Piggin Reviewed-by: Benjamin Coddington --- Hi, This is motivated by a stack overflow described here: https://lore.kernel.org/netdev/20230927001308.749910-1-npiggin@gmail.com/ NFS is not really a major culprit but it seems not too hard to shrink the stack a little. Thanks, Nick fs/nfs/getroot.c | 22 ++++++++++++++-------- 1 file changed, 14 insertions(+), 8 deletions(-) diff --git a/fs/nfs/getroot.c b/fs/nfs/getroot.c index 11ff2b2e060f..6e4188c09639 100644 --- a/fs/nfs/getroot.c +++ b/fs/nfs/getroot.c @@ -68,7 +68,7 @@ int nfs_get_root(struct super_block *s, struct fs_context= *fc) { struct nfs_fs_context *ctx =3D nfs_fc2context(fc); struct nfs_server *server =3D NFS_SB(s), *clone_server; - struct nfs_fsinfo fsinfo; + struct nfs_fsinfo *fsinfo; struct dentry *root; struct inode *inode; char *name; @@ -79,19 +79,23 @@ int nfs_get_root(struct super_block *s, struct fs_conte= xt *fc) if (!name) goto out; =20 - /* get the actual root for this mount */ - fsinfo.fattr =3D nfs_alloc_fattr_with_label(server); - if (fsinfo.fattr =3D=3D NULL) + fsinfo =3D kmalloc(sizeof(*fsinfo), GFP_KERNEL); + if (!fsinfo) goto out_name; =20 - error =3D server->nfs_client->rpc_ops->getroot(server, ctx->mntfh, &fsinf= o); + /* get the actual root for this mount */ + fsinfo->fattr =3D nfs_alloc_fattr_with_label(server); + if (fsinfo->fattr =3D=3D NULL) + goto out_fsinfo; + + error =3D server->nfs_client->rpc_ops->getroot(server, ctx->mntfh, fsinfo= ); if (error < 0) { dprintk("nfs_get_root: getattr error =3D %d\n", -error); nfs_errorf(fc, "NFS: Couldn't getattr on root"); goto out_fattr; } =20 - inode =3D nfs_fhget(s, ctx->mntfh, fsinfo.fattr); + inode =3D nfs_fhget(s, ctx->mntfh, fsinfo->fattr); if (IS_ERR(inode)) { dprintk("nfs_get_root: get root inode failed\n"); error =3D PTR_ERR(inode); @@ -148,11 +152,13 @@ int nfs_get_root(struct super_block *s, struct fs_con= text *fc) !(kflags_out & SECURITY_LSM_NATIVE_LABELS)) server->caps &=3D ~NFS_CAP_SECURITY_LABEL; =20 - nfs_setsecurity(inode, fsinfo.fattr); + nfs_setsecurity(inode, fsinfo->fattr); error =3D 0; =20 out_fattr: - nfs_free_fattr(fsinfo.fattr); + nfs_free_fattr(fsinfo->fattr); +out_fsinfo: + kfree(fsinfo); out_name: kfree(name); out: --=20 2.40.1