Re: [PATCH v2 00/31] vfs: pass S_IFDIR mode to vfs_prepare_mode()

[NeilBrown]

On Tue, 30 Jun 2026, Jori Koolstra wrote:
> There is a comment in vfs_prepare_mode() that says:
> 
> Note that it's currently valid for @type to be 0 if a directory is
> created. Filesystems raise that flag individually and we need to check
> whether each filesystem can deal with receiving S_IFDIR from the vfs
> before we enforce a non-zero type.
> 
> It is useful to do this clean-up ahead of O_CREAT|O_DIRECTORY.
> Specifically, in lookup_open() we need to replace the vfs_prepare_mode()
> with something that also handles dirs. I don't really want to push the
> odd
> 
>     mode = vfs_prepare_mode(idmap, dir, mode, S_IRWXUGO | S_ISVTX, 0);
> 
> further into that code, and neither do I want this to be different from
> the regular vfs_mkdir() path. We can then also match on S_IFMT in
> may_o_create(), instead of passing a bool to signal whether we are
> creating a dir (and assuming 0 means a dir is really ugly).
> 
> It is a bit challenging to verify that passing S_IFDIR is safe, as there
> are many filesystems. Claude Opus 4.8 was used to generate the context
> for each mkdir implementation from which it can be judged whether
> passing S_IFDIR is OK. The result was then verified by hand by looking
> at how the mode argument is used in each case. To check whether all
> mkdir implementations are covered, 'rg "\.mkdir" ' was used and checked
> against the list of uses Claude found.
> 
> It is safe to do this clean-up except that three filesystems (fuse,
> cifs, and coda) forward the mkdir @mode unchanged to something outside
> the kernel. Mask S_IFDIR back out in coda_mkdir(), fuse_mkdir() and
> cifs_mkdir() so that what is sent outside the kernel is unchanged.
> Their maintainers can drop the mask once they have confirmed it is safe.
> For the other filesystems redundant S_IFDIR OR'ing is dropped.

This all looks good to me - thanks.
Reviewed-by: NeilBrown <neil@xxxxxxxxxx>

NeilBrown


> 
> Jori Koolstra (31):
>   vfs: pass S_IFDIR mode to vfs_prepare_mode()
>   9p: drop redundant S_IFDIR from mkdir
>   affs: drop redundant S_IFDIR from mkdir
>   afs: drop redundant S_IFDIR from mkdir
>   autofs: drop redundant S_IFDIR from mkdir
>   btrfs: drop redundant S_IFDIR from mkdir
>   ceph: drop redundant S_IFDIR from mkdir
>   ext2: drop redundant S_IFDIR from mkdir
>   ext4: drop redundant S_IFDIR from mkdir
>   f2fs: drop redundant S_IFDIR from mkdir
>   gfs2: drop redundant S_IFDIR from mkdir
>   hfs: drop redundant S_IFDIR from mkdir
>   hfsplus: drop redundant S_IFDIR from mkdir
>   hpfs: drop redundant S_IFDIR from mkdir
>   hugetlbfs: drop redundant S_IFDIR from mkdir
>   jffs2: drop redundant S_IFDIR from mkdir
>   jfs: drop redundant S_IFDIR from mkdir
>   minix: drop redundant S_IFDIR from mkdir
>   nilfs2: drop redundant S_IFDIR from mkdir
>   ntfs3: drop redundant S_IFDIR from mkdir
>   ocfs2: drop redundant S_IFDIR from mkdir
>   ocfs2: dlmfs: drop redundant S_IFDIR from mkdir
>   omfs: drop redundant S_IFDIR from mkdir
>   orangefs: drop redundant S_IFDIR from mkdir
>   ramfs: drop redundant S_IFDIR from mkdir
>   udf: drop redundant S_IFDIR from mkdir
>   ufs: drop redundant S_IFDIR from mkdir
>   nfs: drop redundant S_IFDIR from mkdir
>   ubifs: drop redundant S_IFDIR from mkdir
>   xfs: drop redundant S_IFDIR from mkdir
>   ntfs: drop redundant S_IFDIR from mkdir
> 
>  fs/9p/vfs_inode.c      | 2 +-
>  fs/9p/vfs_inode_dotl.c | 1 -
>  fs/affs/namei.c        | 2 +-
>  fs/afs/dir.c           | 2 +-
>  fs/autofs/root.c       | 2 +-
>  fs/btrfs/inode.c       | 2 +-
>  fs/ceph/dir.c          | 1 -
>  fs/coda/dir.c          | 7 ++++++-
>  fs/ext2/namei.c        | 2 +-
>  fs/ext4/namei.c        | 2 +-
>  fs/f2fs/namei.c        | 2 +-
>  fs/fuse/dir.c          | 8 ++++++++
>  fs/gfs2/inode.c        | 2 +-
>  fs/hfs/dir.c           | 2 +-
>  fs/hfsplus/dir.c       | 2 +-
>  fs/hpfs/namei.c        | 4 ++--
>  fs/hugetlbfs/inode.c   | 2 +-
>  fs/jffs2/dir.c         | 2 --
>  fs/jfs/namei.c         | 2 +-
>  fs/minix/namei.c       | 2 +-
>  fs/namei.c             | 7 +------
>  fs/nfs/dir.c           | 2 +-
>  fs/nilfs2/namei.c      | 2 +-
>  fs/ntfs/namei.c        | 2 +-
>  fs/ntfs3/namei.c       | 2 +-
>  fs/ocfs2/dlmfs/dlmfs.c | 2 +-
>  fs/ocfs2/namei.c       | 2 +-
>  fs/omfs/dir.c          | 2 +-
>  fs/orangefs/namei.c    | 2 +-
>  fs/ramfs/inode.c       | 2 +-
>  fs/smb/client/inode.c  | 7 +++++++
>  fs/ubifs/dir.c         | 2 +-
>  fs/udf/namei.c         | 2 +-
>  fs/ufs/namei.c         | 2 +-
>  fs/xfs/xfs_iops.c      | 2 +-
>  35 files changed, 51 insertions(+), 40 deletions(-)
> 
> 
> base-commit: dc59e4fea9d83f03bad6bddf3fa2e52491777482
> -- 
> 2.54.0
> 
>