On Tue, 2013-02-12 at 17:07 -0500, J. Bruce Fields wrote:
> On Fri, Feb 08, 2013 at 07:39:14AM -0500, Steve Dickson wrote:
> > From: David Quigley <dpquigl@xxxxxxxxxxxxxxx>
> >
> > In order to mimic the way that NFSv4 ACLs are implemented we have created a
> > structure to be used to pass label data up and down the call chain. This patch
> > adds the new structure and new members to the required NFSv4 call structures.
> >
> > Signed-off-by: Matthew N. Dodd <Matthew.Dodd@xxxxxxxxxx>
> > Signed-off-by: Miguel Rodel Felipe <Rodel_FM@xxxxxxxxxxxxxxxxx>
> > Signed-off-by: Phua Eu Gene <PHUA_Eu_Gene@xxxxxxxxxxxxxxxxx>
> > Signed-off-by: Khin Mi Mi Aung <Mi_Mi_AUNG@xxxxxxxxxxxxxxxxx>
> > ---
> > fs/nfs/inode.c | 33 +++++++++++++++++++++++++++++++++
> > include/linux/nfs4.h | 7 +++++++
> > include/linux/nfs_fs.h | 17 +++++++++++++++++
> > include/linux/nfs_xdr.h | 21 +++++++++++++++++++++
> > include/uapi/linux/nfs4.h | 2 +-
> > 5 files changed, 79 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
> > index ebeb94c..8d5f01b 100644
> > --- a/fs/nfs/inode.c
> > +++ b/fs/nfs/inode.c
> > @@ -255,6 +255,39 @@ nfs_init_locked(struct inode *inode, void *opaque)
> > return 0;
> > }
> >
> > +#ifdef CONFIG_NFS_V4_SECURITY_LABEL
> > +struct nfs4_label *nfs4_label_alloc(struct nfs_server *server, gfp_t flags)
> > +{
> > + struct nfs4_label *label = NULL;
> > +
> > + if (!(server->caps & NFS_CAP_SECURITY_LABEL))
> > + return label;
> > +
> > + label = kzalloc(NFS4_MAXLABELLEN, flags);
> > + if (label == NULL)
> > + return ERR_PTR(-ENOMEM);
> > +
> > + label->label = (char *)(label + 1);
> > + label->len = NFS4_MAXLABELLEN;
>
> If you're expecting to be able to store up to NFS4_MAXLABELLEN of data
> after the end of the struct, then you want:
>
> label = kzalloc(sizeof(struct nfs4_label) + NFS4_MAXLABELLEN, flags);
Sigh... No.
I keep telling Steve that the 'label' needs to be defined as an array,
not a pointer. Having it be a pointer gives rise to a completely
unnecessary extra indirection (the CPU first needs to look up the
content of 'label->label', then dereference that pointer)...
IOW: we should just be defining struct nfs4_label as
struct nfs4_label {
.... lots of definitions ...
char label[NFS4_MAXLABELLEN];
};
in which case the above allocation becomes a trivial
label = kzalloc(sizeof(*label), flags);
> > +
> > + return label;
> > +}
> > +EXPORT_SYMBOL_GPL(nfs4_label_alloc);
> > +
> > +void nfs4_label_init(struct nfs4_label *label)
> > +{
> > + if (label && label->label) {
> > + /* 0 is the null format meaning that the data is not
> > + to be translated */
> > + label->lfs = 0;
> > + label->pi = 0;
> > + label->len = NFS4_MAXLABELLEN;
>
> This logic seems a little odd to me; why would we pass NULL to this?
> Why would we skip the other initialization in the !label->label case?
> Why is NFS4_MAXLABELLEN the default? (And wasn't that just set in
> nfs4_label_alloc?)
>
> But OK maybe I need to read the rest of the patches.
>
> > + }
> > + return;
> > +}
> > +EXPORT_SYMBOL_GPL(nfs4_label_init);
> > +#endif
>
> > diff --git a/include/uapi/linux/nfs4.h b/include/uapi/linux/nfs4.h
> > index 788128e..b8014a2 100644
> > --- a/include/uapi/linux/nfs4.h
> > +++ b/include/uapi/linux/nfs4.h
> > @@ -25,7 +25,7 @@
> > #define NFS4_MAXNAMLEN NAME_MAX
> > #define NFS4_OPAQUE_LIMIT 1024
> > #define NFS4_MAX_SESSIONID_LEN 16
> > -
> > +#define NFS4_MAXLABELLEN (4095 - offsetof(struct nfs4_label , label))
>
> The way you've defined things, that should be just
>
> (4095 - sizeof(struct nfs4_label))
No. See above. If the 'label' field is an array, then the offsetof() is
100% correct.
> (Is there typically some more alloc overhead that would push this
> allocation over 4k? I don't know well enough how the allocator(s) work
> to answer that.)
>
> --b.
>
> > #define NFS4_ACCESS_READ 0x0001
> > #define NFS4_ACCESS_LOOKUP 0x0002
> > #define NFS4_ACCESS_MODIFY 0x0004
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