linux-ext4 - Re: [PATCH 07/31] fuse: create a per-inode flag for toggling iomap

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAJnrk1ZYp=+ho02gMAPGLsGBo3a84ScuE92xP68=1SR-ixAs+g@mail.gmail.com>
Date: Fri, 23 Jan 2026 10:05:32 -0800
From: Joanne Koong <joannelkoong@...il.com>
To: "Darrick J. Wong" <djwong@...nel.org>
Cc: miklos@...redi.hu, bernd@...ernd.com, neal@...pa.dev, 
	linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 07/31] fuse: create a per-inode flag for toggling iomap

On Thu, Jan 22, 2026 at 2:22 PM Darrick J. Wong <djwong@...nel.org> wrote:
>
> On Wed, Jan 21, 2026 at 05:13:39PM -0800, Joanne Koong wrote:
> > On Tue, Oct 28, 2025 at 5:46 PM Darrick J. Wong <djwong@...nel.org> wrote:
> > >
> > > From: Darrick J. Wong <djwong@...nel.org>
> > >
> > > Create a per-inode flag to control whether or not this inode actually
> > > uses iomap.  This is required for non-regular files because iomap
> > > doesn't apply there; and enables fuse filesystems to provide some
> > > non-iomap files if desired.
> > >
> > > Signed-off-by: "Darrick J. Wong" <djwong@...nel.org>
> >
> > The logic in this makes sense to me, left just a few comments below.
> >
> > Reviewed-by: Joanne Koong <joannelkoong@...il.com>
>
> Thanks!
>
> > > ---
> > >  fs/fuse/fuse_i.h          |   17 ++++++++++++++++
> > >  include/uapi/linux/fuse.h |    3 +++
> > >  fs/fuse/file.c            |    1 +
> > >  fs/fuse/file_iomap.c      |   49 +++++++++++++++++++++++++++++++++++++++++++++
> > >  fs/fuse/inode.c           |   26 ++++++++++++++++++------
> > >  5 files changed, 90 insertions(+), 6 deletions(-)
> > >
> > > diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> > > index f1ef77a0be05bb..42c85c19f3b13b 100644
> > > --- a/fs/fuse/file.c
> > > +++ b/fs/fuse/file.c
> > > +void fuse_iomap_init_reg_inode(struct inode *inode, unsigned attr_flags)
> > > +{
> > > +       struct fuse_conn *conn = get_fuse_conn(inode);
> > > +       struct fuse_inode *fi = get_fuse_inode(inode);
> > > +
> > > +       ASSERT(S_ISREG(inode->i_mode));
> > > +
> > > +       if (conn->iomap && (attr_flags & FUSE_ATTR_IOMAP)) {
> > > +               set_bit(FUSE_I_EXCLUSIVE, &fi->state);
> > > +               fuse_inode_set_iomap(inode);
> > > +       }
> > > +}
> > > +
> > > +void fuse_iomap_evict_inode(struct inode *inode)
> > > +{
> > > +       struct fuse_conn *conn = get_fuse_conn(inode);
> > > +       struct fuse_inode *fi = get_fuse_inode(inode);
> > > +
> > > +       if (fuse_inode_has_iomap(inode))
> >
> > If I'm understanding this correctly, a fuse inode can't have
> > FUSE_I_IOMAP set on it if conn>iomap is not enabled, correct?
>
> Correct.
>
> > Maybe it makes sense to just return if (!conn->iomap) at the very
> > beginning, to make that more clear?
>
> <shrug> fuse_inode_has_iomap only checks FUSE_I_IOMAP...
>
> > > +               fuse_inode_clear_iomap(inode);
> > > +       if (conn->iomap && fuse_inode_is_exclusive(inode))
> > > +               clear_bit(FUSE_I_EXCLUSIVE, &fi->state);
>
> ...but I wasn't going to assume that iomap is the only way that
> FUSE_I_EXCLUSIVE could get set.
>
> On the other hand, for non-regular files we set FUSE_I_EXCLUSIVE only if
> conn->iomap is nonzero *and* attr->flags contains FUSE_ATTR_IOMAP.  So
> this clearing code isn't quite the same as the setting code.
>
> I wonder if that means we should set FUSE_I_IOMAP for non-regular files?
> They don't use iomap itself, but I suppose it would be neat if "iomap
> directories" also meant that timestamps and whatnot worked in the same
> as they do for regular files.
>

That seems like a good idea to me. I think that also makes the mental
model (at least for me) simpler.

Thanks,
Joanne