From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f45.google.com ([209.85.218.45]:33422 "EHLO mail-oi0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755146AbcFQDMb (ORCPT ); Thu, 16 Jun 2016 23:12:31 -0400 Received: by mail-oi0-f45.google.com with SMTP id u201so99110802oie.0 for ; Thu, 16 Jun 2016 20:12:30 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20160616083807.GB7409@1wt.eu> References: <20160615235047.GA14480@ZenIV.linux.org.uk> <20160616054525.GA6803@1wt.eu> <20160616065738.GA7154@1wt.eu> <20160616070821.GB14480@ZenIV.linux.org.uk> <20160616072557.GA7336@1wt.eu> <20160616080229.GC14480@ZenIV.linux.org.uk> <20160616082038.GA7409@1wt.eu> <20160616083807.GB7409@1wt.eu> From: Andy Lutomirski Date: Thu, 16 Jun 2016 20:12:08 -0700 Message-ID: Subject: Re: [PATCH v2 1/2] fs: Improve and simplify copy_mount_options To: Willy Tarreau Cc: Al Viro , Linus Torvalds , Andy Lutomirski , Linux FS Devel , Stephen Rothwell , Andrew Morton , stable Content-Type: text/plain; charset=UTF-8 Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Thu, Jun 16, 2016 at 1:38 AM, Willy Tarreau wrote: > On Thu, Jun 16, 2016 at 10:20:38AM +0200, Willy Tarreau wrote: >> However if the initial point was to avoid reading extra >> pages most of the time, we could possibly consider that the string >> copy is an optimization for the case where we have the information >> available. Thus if !fstype || !(type->fs_flags & FS_BINARY_MOUNTDATA) >> then we use copy_mount_options() otherwise we use copy_mount_string(). >> It will only leave the full page copy for mount --bind or -o remount >> then. > > For example like this (not compile-tested either) : I like this approach. Al, is this okay with you? --Andy > > diff --git a/fs/compat.c b/fs/compat.c > index be6e48b..6407d40 100644 > --- a/fs/compat.c > +++ b/fs/compat.c > @@ -795,18 +795,26 @@ COMPAT_SYSCALL_DEFINE5(mount, const char __user *, dev_name, > void *options; > char *kernel_dev; > int retval; > + bool use_str = false; > + struct file_system_type *fstype; > > kernel_type = copy_mount_string(type); > retval = PTR_ERR(kernel_type); > if (IS_ERR(kernel_type)) > goto out; > > + if (kernel_type && (fstype = get_fs_type(kernel_type)) { > + if (!(fstype->fs_flags & FS_BINARY_MOUNTDATA)) > + use_str = true; > + put_filesystem(fstype); > + } > + > kernel_dev = copy_mount_string(dev_name); > retval = PTR_ERR(kernel_dev); > if (IS_ERR(kernel_dev)) > goto out1; > > - options = copy_mount_options(data); > + options = use_str ? copy_mount_string(data) : copy_mount_options(data); > retval = PTR_ERR(options); > if (IS_ERR(options)) > goto out2; > diff --git a/fs/namespace.c b/fs/namespace.c > index 4fb1691..f14089d 100644 > --- a/fs/namespace.c > +++ b/fs/namespace.c > @@ -2906,18 +2906,26 @@ SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name, > char *kernel_type; > char *kernel_dev; > void *options; > + bool use_str = false; > + struct file_system_type *fstype; > > kernel_type = copy_mount_string(type); > ret = PTR_ERR(kernel_type); > if (IS_ERR(kernel_type)) > goto out_type; > > + if (kernel_type && (fstype = get_fs_type(kernel_type)) { > + if (!(fstype->fs_flags & FS_BINARY_MOUNTDATA)) > + use_str = true; > + put_filesystem(fstype); > + } > + > kernel_dev = copy_mount_string(dev_name); > ret = PTR_ERR(kernel_dev); > if (IS_ERR(kernel_dev)) > goto out_dev; > > - options = copy_mount_options(data); > + options = use_str ? copy_mount_string(data) : copy_mount_options(data); > ret = PTR_ERR(options); > if (IS_ERR(options)) > goto out_data; -- Andy Lutomirski AMA Capital Management, LLC