From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Hansen Subject: [RFC][PATCH 20/20] honor r/w changes at do_remount() time Date: Fri, 16 Jun 2006 16:12:28 -0700 Message-ID: <20060616231228.2107A2EE@localhost.localdomain> References: <20060616231213.D4C5D6AF@localhost.localdomain> Cc: linux-fsdevel@vger.kernel.org, herbert@13thfloor.at, viro@ftp.linux.org.uk, Dave Hansen Return-path: Received: from e35.co.us.ibm.com ([32.97.110.153]:12960 "EHLO e35.co.us.ibm.com") by vger.kernel.org with ESMTP id S932121AbWFPXMd (ORCPT ); Fri, 16 Jun 2006 19:12:33 -0400 To: linux-kernel@vger.kernel.org In-Reply-To: <20060616231213.D4C5D6AF@localhost.localdomain> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org Originally from: Herbert Poetzl This is the core of the read-only bind mount patch set. Note that this does _not_ add a "ro" option directly to the bind mount operation. If you require such a mount, you must first do the bind, then follow it up with a 'mount -o remount,ro' operation. Signed-off-by: Dave Hansen --- lxc-dave/fs/namespace.c | 27 +++++++++++++++++++++++++-- lxc-dave/fs/open.c | 2 +- lxc-dave/include/linux/mount.h | 1 - 3 files changed, 26 insertions(+), 4 deletions(-) diff -puN fs/namespace.c~C-D8-actually-add-flags fs/namespace.c --- lxc/fs/namespace.c~C-D8-actually-add-flags 2006-06-16 15:58:12.000000000 -0700 +++ lxc-dave/fs/namespace.c 2006-06-16 15:58:12.000000000 -0700 @@ -378,7 +378,10 @@ static int show_vfsmnt(struct seq_file * seq_path(m, mnt, mnt->mnt_root, " \t\n\\"); seq_putc(m, ' '); mangle(m, mnt->mnt_sb->s_type->name); - seq_puts(m, mnt->mnt_sb->s_flags & MS_RDONLY ? " ro" : " rw"); + if ((mnt->mnt_sb->s_flags & MS_RDONLY) || __mnt_is_readonly(mnt)) + seq_puts(m, " ro"); + else + seq_puts(m, " rw"); for (fs_infop = fs_info; fs_infop->flag; fs_infop++) { if (mnt->mnt_sb->s_flags & fs_infop->flag) seq_puts(m, fs_infop->str); @@ -947,6 +950,23 @@ out: return err; } +static int change_mount_flags(struct vfsmount *mnt, int ms_flags) +{ + int error = 0; + int readonly_request = 0; + + if (ms_flags & MS_RDONLY) + readonly_request = 1; + if (readonly_request == __mnt_is_readonly(mnt)) + return 0; + + if (readonly_request) + error = mnt_make_readonly(mnt); + else + __mnt_make_writable(mnt); + return error; +} + /* * change filesystem flags. dir should be a physical root of filesystem. * If you've mounted a non-root directory somewhere and want to do remount @@ -968,7 +988,10 @@ static int do_remount(struct nameidata * return -EINVAL; down_write(&sb->s_umount); - err = do_remount_sb(sb, flags, data, 0); + if (flags & MS_BIND) + err = change_mount_flags(nd->mnt, flags); + else + err = do_remount_sb(sb, flags, data, 0); if (!err) nd->mnt->mnt_flags = mnt_flags; up_write(&sb->s_umount); diff -puN fs/open.c~C-D8-actually-add-flags fs/open.c --- lxc/fs/open.c~C-D8-actually-add-flags 2006-06-16 15:58:12.000000000 -0700 +++ lxc-dave/fs/open.c 2006-06-16 15:58:12.000000000 -0700 @@ -546,7 +546,7 @@ asmlinkage long sys_faccessat(int dfd, c special_file(nd.dentry->d_inode->i_mode)) goto out_path_release; - if(IS_RDONLY(nd.dentry->d_inode)) + if(__mnt_is_readonly(nd.mnt) || IS_RDONLY(nd.dentry->d_inode)) res = -EROFS; out_path_release: diff -puN include/linux/mount.h~C-D8-actually-add-flags include/linux/mount.h --- lxc/include/linux/mount.h~C-D8-actually-add-flags 2006-06-16 15:58:12.000000000 -0700 +++ lxc-dave/include/linux/mount.h 2006-06-16 15:58:12.000000000 -0700 @@ -87,7 +87,6 @@ static inline void __mnt_make_writable(s WARN_ON(atomic_read(&mnt->mnt_writers)); atomic_inc(&mnt->mnt_writers); } - static inline int __mnt_is_readonly(struct vfsmount *mnt) { return (atomic_read(&mnt->mnt_writers) == 0); _