Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934794AbYBOWx3 (ORCPT ); Fri, 15 Feb 2008 17:53:29 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932181AbYBOWiO (ORCPT ); Fri, 15 Feb 2008 17:38:14 -0500 Received: from e1.ny.us.ibm.com ([32.97.182.141]:36379 "EHLO e1.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932132AbYBOWiF (ORCPT ); Fri, 15 Feb 2008 17:38:05 -0500 Subject: [PATCH 29/30] r/o bind mounts: honor mount writer counts at remount To: linux-kernel@vger.kernel.org Cc: hch@lst.de, miklos@szeredi.hu, akpm@osdl.org, Dave Hansen From: Dave Hansen Date: Fri, 15 Feb 2008 14:38:00 -0800 References: <20080215223721.9E0A088A@kernel> In-Reply-To: <20080215223721.9E0A088A@kernel> Message-Id: <20080215223800.323B2B5B@kernel> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4872 Lines: 149 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: If you wish to have a r/o bind mount of /foo on bar: mount --bind /foo /bar mount -o remount,ro /bar Acked-by: Al Viro Signed-off-by: Christoph Hellwig Signed-off-by: Dave Hansen Signed-off-by: Andrew Morton --- linux-2.6.git-dave/fs/namespace.c | 50 ++++++++++++++++++++++++++----- linux-2.6.git-dave/include/linux/mount.h | 1 2 files changed, 44 insertions(+), 7 deletions(-) diff -puN fs/namespace.c~r-o-bind-mounts-honor-r-w-changes-at-do_remount-time fs/namespace.c --- linux-2.6.git/fs/namespace.c~r-o-bind-mounts-honor-r-w-changes-at-do_remount-time 2008-02-15 13:25:59.000000000 -0800 +++ linux-2.6.git-dave/fs/namespace.c 2008-02-15 13:25:59.000000000 -0800 @@ -105,7 +105,11 @@ struct vfsmount *alloc_vfsmnt(const char */ int __mnt_is_readonly(struct vfsmount *mnt) { - return (mnt->mnt_sb->s_flags & MS_RDONLY); + if (mnt->mnt_flags & MNT_READONLY) + return 1; + if (mnt->mnt_sb->s_flags & MS_RDONLY) + return 1; + return 0; } EXPORT_SYMBOL_GPL(__mnt_is_readonly); @@ -299,7 +303,7 @@ void mnt_drop_write(struct vfsmount *mnt } EXPORT_SYMBOL_GPL(mnt_drop_write); -int mnt_make_readonly(struct vfsmount *mnt) +static int mnt_make_readonly(struct vfsmount *mnt) { int ret = 0; @@ -312,15 +316,25 @@ int mnt_make_readonly(struct vfsmount *m goto out; } /* - * actually set mount's r/o flag here to make - * __mnt_is_readonly() true, which keeps anyone - * from doing a successful mnt_want_write(). + * nobody can do a successful mnt_want_write() with all + * of the counts in MNT_DENIED_WRITE and the locks held. */ + spin_lock(&vfsmount_lock); + if (!ret) + mnt->mnt_flags |= MNT_READONLY; + spin_unlock(&vfsmount_lock); out: unlock_mnt_writers(); return ret; } +static void __mnt_unmake_readonly(struct vfsmount *mnt) +{ + spin_lock(&vfsmount_lock); + mnt->mnt_flags &= ~MNT_READONLY; + spin_unlock(&vfsmount_lock); +} + int simple_set_mnt(struct vfsmount *mnt, struct super_block *sb) { mnt->mnt_sb = sb; @@ -683,7 +697,7 @@ static int show_vfsmnt(struct seq_file * seq_putc(m, '.'); mangle(m, mnt->mnt_sb->s_subtype); } - seq_puts(m, mnt->mnt_sb->s_flags & MS_RDONLY ? " ro" : " rw"); + seq_puts(m, __mnt_is_readonly(mnt) ? " ro" : " 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); @@ -1277,6 +1291,23 @@ 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_unmake_readonly(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 @@ -1299,7 +1330,10 @@ static noinline int do_remount(struct na return -EINVAL; down_write(&sb->s_umount); - err = do_remount_sb(sb, flags, data, 0); + if (flags & MS_BIND) + err = change_mount_flags(nd->path.mnt, flags); + else + err = do_remount_sb(sb, flags, data, 0); if (!err) nd->path.mnt->mnt_flags = mnt_flags; up_write(&sb->s_umount); @@ -1752,6 +1786,8 @@ long do_mount(char *dev_name, char *dir_ mnt_flags |= MNT_NODIRATIME; if (flags & MS_RELATIME) mnt_flags |= MNT_RELATIME; + if (flags & MS_RDONLY) + mnt_flags |= MNT_READONLY; flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT); diff -puN include/linux/mount.h~r-o-bind-mounts-honor-r-w-changes-at-do_remount-time include/linux/mount.h --- linux-2.6.git/include/linux/mount.h~r-o-bind-mounts-honor-r-w-changes-at-do_remount-time 2008-02-15 13:25:59.000000000 -0800 +++ linux-2.6.git-dave/include/linux/mount.h 2008-02-15 13:25:59.000000000 -0800 @@ -29,6 +29,7 @@ struct mnt_namespace; #define MNT_NOATIME 0x08 #define MNT_NODIRATIME 0x10 #define MNT_RELATIME 0x20 +#define MNT_READONLY 0x40 /* does the user want this to be r/o? */ #define MNT_SHRINKABLE 0x100 #define MNT_IMBALANCED_WRITE_COUNT 0x200 /* just for debugging */ _ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/