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From: Amir Goldstein <amir73il@gmail.com>
Date: Thu, 4 Jan 2024 09:46:07 +0200
Message-ID: <CAOQ4uxhKVaL3gvwrURSWFSBf2HH6vg0qwM1LVPkmQLfnvTPrdw@mail.gmail.com>
Subject: Re: [PATCH v2 2/2] fs: Create a generic is_dot_dotdot() utility
To: Jeff Layton <jlayton@kernel.org>
Cc: Chuck Lever <cel@kernel.org>, Chuck Lever <chuck.lever@oracle.com>, 
	linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org, 
	trondmy@hammerspace.com, viro@zeniv.linux.org.uk, brauner@kernel.org
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On Wed, Jan 3, 2024 at 9:08=E2=80=AFPM Jeff Layton <jlayton@kernel.org> wro=
te:
>
> On Wed, 2024-01-03 at 10:19 -0500, Chuck Lever wrote:
> > From: Chuck Lever <chuck.lever@oracle.com>
> >
> > De-duplicate the same functionality in several places by hoisting
> > the is_dot_dotdot() function into linux/fs.h.
> >
> > Suggested-by: Amir Goldstein <amir73il@gmail.com>
> > Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
> > ---
> >  fs/crypto/fname.c    |    8 +-------
> >  fs/ecryptfs/crypto.c |   10 ----------
> >  fs/exportfs/expfs.c  |    4 +---
> >  fs/f2fs/f2fs.h       |   11 -----------
> >  include/linux/fs.h   |    9 +++++++++
> >  5 files changed, 11 insertions(+), 31 deletions(-)
> >
> > diff --git a/fs/crypto/fname.c b/fs/crypto/fname.c
> > index 7b3fc189593a..0ad52fbe51c9 100644
> > --- a/fs/crypto/fname.c
> > +++ b/fs/crypto/fname.c
> > @@ -74,13 +74,7 @@ struct fscrypt_nokey_name {
> >
> >  static inline bool fscrypt_is_dot_dotdot(const struct qstr *str)
> >  {
> > -     if (str->len =3D=3D 1 && str->name[0] =3D=3D '.')
> > -             return true;
> > -
> > -     if (str->len =3D=3D 2 && str->name[0] =3D=3D '.' && str->name[1] =
=3D=3D '.')
> > -             return true;
> > -
> > -     return false;
> > +     return is_dot_dotdot(str->name, str->len);
> >  }
> >
> >  /**
> > diff --git a/fs/ecryptfs/crypto.c b/fs/ecryptfs/crypto.c
> > index 03bd55069d86..2fe0f3af1a08 100644
> > --- a/fs/ecryptfs/crypto.c
> > +++ b/fs/ecryptfs/crypto.c
> > @@ -1949,16 +1949,6 @@ int ecryptfs_encrypt_and_encode_filename(
> >       return rc;
> >  }
> >
> > -static bool is_dot_dotdot(const char *name, size_t name_size)
> > -{
> > -     if (name_size =3D=3D 1 && name[0] =3D=3D '.')
> > -             return true;
> > -     else if (name_size =3D=3D 2 && name[0] =3D=3D '.' && name[1] =3D=
=3D '.')
> > -             return true;
> > -
> > -     return false;
> > -}
> > -
> >  /**
> >   * ecryptfs_decode_and_decrypt_filename - converts the encoded cipher =
text name to decoded plaintext
> >   * @plaintext_name: The plaintext name
> > diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c
> > index 84af58eaf2ca..07ea3d62b298 100644
> > --- a/fs/exportfs/expfs.c
> > +++ b/fs/exportfs/expfs.c
> > @@ -255,9 +255,7 @@ static bool filldir_one(struct dir_context *ctx, co=
nst char *name, int len,
> >               container_of(ctx, struct getdents_callback, ctx);
> >
> >       buf->sequence++;
> > -     /* Ignore the '.' and '..' entries */
> > -     if ((len > 2 || name[0] !=3D '.' || (len =3D=3D 2 && name[1] !=3D=
 '.')) &&
> > -         buf->ino =3D=3D ino && len <=3D NAME_MAX) {
> > +     if (buf->ino =3D=3D ino && len <=3D NAME_MAX && !is_dot_dotdot(na=
me, len)) {
> >               memcpy(buf->name, name, len);
> >               buf->name[len] =3D '\0';
> >               buf->found =3D 1;
> > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> > index 9043cedfa12b..322a3b8a3533 100644
> > --- a/fs/f2fs/f2fs.h
> > +++ b/fs/f2fs/f2fs.h
> > @@ -3368,17 +3368,6 @@ static inline bool f2fs_cp_error(struct f2fs_sb_=
info *sbi)
> >       return is_set_ckpt_flags(sbi, CP_ERROR_FLAG);
> >  }
> >
> > -static inline bool is_dot_dotdot(const u8 *name, size_t len)
> > -{
> > -     if (len =3D=3D 1 && name[0] =3D=3D '.')
> > -             return true;
> > -
> > -     if (len =3D=3D 2 && name[0] =3D=3D '.' && name[1] =3D=3D '.')
> > -             return true;
> > -
> > -     return false;
> > -}
> > -
> >  static inline void *f2fs_kmalloc(struct f2fs_sb_info *sbi,
> >                                       size_t size, gfp_t flags)
> >  {
> > diff --git a/include/linux/fs.h b/include/linux/fs.h
> > index 98b7a7a8c42e..179eea797c22 100644
> > --- a/include/linux/fs.h
> > +++ b/include/linux/fs.h
> > @@ -2846,6 +2846,15 @@ extern bool path_is_under(const struct path *, c=
onst struct path *);
> >
> >  extern char *file_path(struct file *, char *, int);
> >
> > +static inline bool is_dot_dotdot(const char *name, size_t len)
> > +{
> > +     if (len =3D=3D 1 && name[0] =3D=3D '.')
> > +             return true;
> > +     if (len =3D=3D 2 && name[0] =3D=3D '.' && name[1] =3D=3D '.')
> > +             return true;
> > +     return false;
> > +}
> > +
> >  #include <linux/err.h>
> >
> >  /* needed for stackable file system support */
> >
> >
>
> Looks good to me. I took a quick look to see if there were other open-
> coded versions, but I didn't see any.
>

The outstanding open-coded version that wasn't deduped is in
lookup_one_common(), which is the version that Trond used and
mentioned in his patch.

It is also a slightly more "efficient" version, but I have no idea if
that really matters.

In any case, having lookup_one_common() and get_name() use
the same helper is clearly prefered, because the check in lookup_one()
is the declared reason for the get_name() patch.

Thanks,
Amir.