Originally from: Herbert Poetzl This is the core of the read-only bind mount patch set. This patch introduces MNT_RDONLY and ensures that it is propagated into vfsmount->mnt_flags via do_loopback(). It then modifies inode_is_readonly() and file_readonly() to check for the flag. DESC mnt_may_-checks EDESC Originally from: Herbert Poetzl This part adds mnt_may_create() and mnt_may_unlink() checks and uses them in lookup_create(), sys_rmdir() and sys_unlink() it also adds a RDONLY check to generic_write_checks(). check with Trond Myklebust about duplicate checks Original versions: +static inline int mnt_may_create(struct vfsmount *mnt, struct inode *dir, + struct dentry *child) +{ + if (child->d_inode) + return -EEXIST; + if (IS_DEADDIR(dir)) + return -ENOENT; + if (mnt_flag_set(mnt, MNT_RDONLY)) + return -EROFS; + return 0; +} + +static inline int ent_may_unlink(struct vfsmount *mnt, struct dentry *child) +{ + if (!child->d_inode) + return -ENOENT; + if (mnt_flag_set(mnt, MNT_RDONLY)) + return -EROFS; + return 0; +} Why do we need the child and IS_DEADDDIR checks? DESC include-mount.h EDESC Signed-off-by: Dave Hansen --- lxc-dave/fs/file.c | 4 +++- lxc-dave/fs/inode.c | 2 +- lxc-dave/fs/namespace.c | 8 ++++++-- lxc-dave/include/linux/mount.h | 1 + lxc-dave/mm/filemap.c | 3 +++ 5 files changed, 14 insertions(+), 4 deletions(-) diff -puN fs/file.c~D8-actually-add-flags fs/file.c --- lxc/fs/file.c~D8-actually-add-flags 2006-05-31 12:48:55.000000000 -0700 +++ lxc-dave/fs/file.c 2006-05-31 12:48:55.000000000 -0700 @@ -12,6 +12,7 @@ #include #include #include +#include #include #include #include @@ -379,6 +380,7 @@ void __init files_defer_init(void) int file_readonly(struct file *file) { - return IS_RDONLY(file->f_dentry->d_inode); + return IS_RDONLY(file->f_dentry->d_inode) || + mnt_flag_set(file->f_vfsmnt, MNT_RDONLY); } diff -puN fs/inode.c~D8-actually-add-flags fs/inode.c --- lxc/fs/inode.c~D8-actually-add-flags 2006-05-31 12:48:55.000000000 -0700 +++ lxc-dave/fs/inode.c 2006-05-31 12:48:55.000000000 -0700 @@ -1420,5 +1420,5 @@ EXPORT_SYMBOL(init_special_inode); int inode_is_readonly(struct inode *inode, struct vfsmount *mnt) { - return IS_RDONLY(inode); + return IS_RDONLY(inode) || mnt_flag_set(mnt, MNT_RDONLY); } diff -puN fs/namespace.c~D8-actually-add-flags fs/namespace.c --- lxc/fs/namespace.c~D8-actually-add-flags 2006-05-31 12:48:55.000000000 -0700 +++ lxc-dave/fs/namespace.c 2006-05-31 12:48:55.000000000 -0700 @@ -900,7 +900,8 @@ static int do_change_type(struct nameida /* * do loopback mount. */ -static int do_loopback(struct nameidata *nd, char *old_name, int recurse) +static int do_loopback(struct nameidata *nd, char *old_name, + int recurse, int mnt_flags) { struct nameidata old_nd; struct vfsmount *mnt = NULL; @@ -938,6 +939,7 @@ static int do_loopback(struct nameidata spin_unlock(&vfsmount_lock); release_mounts(&umount_list); } + mnt->mnt_flags = mnt_flags; out: up_write(&namespace_sem); @@ -1398,6 +1400,8 @@ long do_mount(char *dev_name, char *dir_ ((char *)data_page)[PAGE_SIZE - 1] = 0; /* Separate the per-mountpoint flags */ + if (flags & MS_RDONLY) + mnt_flags |= MNT_RDONLY; if (flags & MS_NOSUID) mnt_flags |= MNT_NOSUID; if (flags & MS_NODEV) @@ -1425,7 +1429,7 @@ long do_mount(char *dev_name, char *dir_ retval = do_remount(&nd, flags & ~MS_REMOUNT, mnt_flags, data_page); else if (flags & MS_BIND) - retval = do_loopback(&nd, dev_name, flags & MS_REC); + retval = do_loopback(&nd, dev_name, flags & MS_REC, mnt_flags); else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) retval = do_change_type(&nd, flags); else if (flags & MS_MOVE) diff -puN include/linux/mount.h~D8-actually-add-flags include/linux/mount.h --- lxc/include/linux/mount.h~D8-actually-add-flags 2006-05-31 12:48:55.000000000 -0700 +++ lxc-dave/include/linux/mount.h 2006-05-31 12:48:55.000000000 -0700 @@ -22,6 +22,7 @@ #define MNT_NOEXEC 0x04 #define MNT_NOATIME 0x08 #define MNT_NODIRATIME 0x10 +#define MNT_RDONLY 0x20 #define MNT_SHRINKABLE 0x100 diff -puN mm/filemap.c~D8-actually-add-flags mm/filemap.c --- lxc/mm/filemap.c~D8-actually-add-flags 2006-05-31 12:48:55.000000000 -0700 +++ lxc-dave/mm/filemap.c 2006-05-31 12:48:55.000000000 -0700 @@ -23,6 +23,7 @@ #include #include #include +#include #include #include #include @@ -1872,6 +1873,8 @@ inline int generic_write_checks(struct f return -EINVAL; if (!isblk) { + if (mnt_flag_set(file->f_vfsmnt, MNT_RDONLY)) + return -EROFS; /* FIXME: this is for backwards compatibility with 2.4 */ if (file->f_flags & O_APPEND) *pos = i_size_read(inode); _