[PATCH 28/28] honor r/w changes at do_remount() time

Dave Hansen
2006-08-01T23:58:38Z

Originally from: Herbert Poetzl <herbert@13thfloor.at>

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 <haveblue@us.ibm.com>
---

lxc-dave/fs/namespace.c | 24 ++++++++++++++++++++++--
lxc-dave/fs/open.c | 2 +-
2 files changed, 23 insertions(+), 3 deletions(-)

diff -puN fs/namespace.c~C-D8-actually-add-flags fs/namespace.c
--- lxc/fs/namespace.c~C-D8-actually-add-flags 2006-08-01 16:35:26.000000000 -0700
+++ lxc-dave/fs/namespace.c 2006-08-01 16:35:34.000000000 -0700
@@ -391,7 +391,7 @@ 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");
+ 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);
@@ -1014,6 +1014,23 @@ 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
@@ -1035,7 +1052,10 @@ 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 (!(sb->s_flags & MS_RDONLY))
mnt_flags |= MNT_SB_WRITABLE;
if (!err)
diff -puN fs/open.c~C-D8-actually-add-flags fs/open.c
--- lxc/fs/open.c~C-D8-actually-add-flags 2006-08-01 16:35:30.000000000 -0700
+++ lxc-dave/fs/open.c 2006-08-01 16:35:34.000000000 -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:
_