Re: [PATCH 1/6] nfsd: prepare for supporting admin-revocation of state

[Chuck Lever III <chuck.lever@oracle.com>]

> On Nov 2, 2023, at 1:24 PM, Jeff Layton <jlayton@kernel.org> wrote:
> 
> On Fri, 2023-11-03 at 07:03 +1100, NeilBrown wrote:
>> On Thu, 02 Nov 2023, Jeff Layton wrote:
>>> On Wed, 2023-11-01 at 11:57 +1100, NeilBrown wrote:
>>>> The NFSv4 protocol allows state to be revoked by the admin and has error
>>>> codes which allow this to be communicated to the client.
>>>> 
>>>> This patch
>>>> - introduces 3 new state-id types for revoked open, lock, and
>>>>   delegation state.  This requires the bitmask to be 'short',
>>>>   not 'char'
>>>> - reports NFS4ERR_ADMIN_REVOKED when these are accessed
>>>> - introduces a per-client counter of these states and returns
>>>>   SEQ4_STATUS_ADMIN_STATE_REVOKED when the counter is not zero.
>>>>   Decrement this when freeing any admin-revoked state.
>>>> - introduces stub code to find all interesting states for a given
>>>>   superblock so they can be revoked via the 'unlock_filesystem'
>>>>   file in /proc/fs/nfsd/
>>>>   No actual states are handled yet.
>>>> 
>>>> Signed-off-by: NeilBrown <neilb@suse.de>
>>>> ---
>>>> fs/nfsd/nfs4layouts.c |  2 +-
>>>> fs/nfsd/nfs4state.c   | 93 +++++++++++++++++++++++++++++++++++++++----
>>>> fs/nfsd/nfsctl.c      |  1 +
>>>> fs/nfsd/nfsd.h        |  1 +
>>>> fs/nfsd/state.h       | 35 +++++++++++-----
>>>> fs/nfsd/trace.h       |  8 +++-
>>>> 6 files changed, 120 insertions(+), 20 deletions(-)
>>>> 
>>>> diff --git a/fs/nfsd/nfs4layouts.c b/fs/nfsd/nfs4layouts.c
>>>> index 5e8096bc5eaa..09d0363bfbc4 100644
>>>> --- a/fs/nfsd/nfs4layouts.c
>>>> +++ b/fs/nfsd/nfs4layouts.c
>>>> @@ -269,7 +269,7 @@ nfsd4_preprocess_layout_stateid(struct svc_rqst *rqstp,
>>>> {
>>>> struct nfs4_layout_stateid *ls;
>>>> struct nfs4_stid *stid;
>>>> - unsigned char typemask = NFS4_LAYOUT_STID;
>>>> + unsigned short typemask = NFS4_LAYOUT_STID;
>>>> __be32 status;
>>>> 
>>>> if (create)
>>>> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
>>>> index 65fd5510323a..f3ba53a16105 100644
>>>> --- a/fs/nfsd/nfs4state.c
>>>> +++ b/fs/nfsd/nfs4state.c
>>>> @@ -1202,6 +1202,13 @@ alloc_init_deleg(struct nfs4_client *clp, struct nfs4_file *fp,
>>>> return NULL;
>>>> }
>>>> 
>>>> +void nfs4_unhash_stid(struct nfs4_stid *s)
>>>> +{
>>>> + if (s->sc_type & NFS4_ALL_ADMIN_REVOKED_STIDS)
>>>> + atomic_dec(&s->sc_client->cl_admin_revoked);
>>>> + s->sc_type = 0;
>>>> +}
>>>> +
>>>> void
>>>> nfs4_put_stid(struct nfs4_stid *s)
>>>> {
>>>> @@ -1215,6 +1222,7 @@ nfs4_put_stid(struct nfs4_stid *s)
>>>> return;
>>>> }
>>>> idr_remove(&clp->cl_stateids, s->sc_stateid.si_opaque.so_id);
>>>> + nfs4_unhash_stid(s);
>>>> nfs4_free_cpntf_statelist(clp->net, s);
>>>> spin_unlock(&clp->cl_lock);
>>>> s->sc_free(s);
>>>> @@ -1265,11 +1273,6 @@ static void destroy_unhashed_deleg(struct nfs4_delegation *dp)
>>>> nfs4_put_stid(&dp->dl_stid);
>>>> }
>>>> 
>>>> -void nfs4_unhash_stid(struct nfs4_stid *s)
>>>> -{
>>>> - s->sc_type = 0;
>>>> -}
>>>> -
>>>> /**
>>>>  * nfs4_delegation_exists - Discover if this delegation already exists
>>>>  * @clp:     a pointer to the nfs4_client we're granting a delegation to
>>>> @@ -1536,6 +1539,7 @@ static void put_ol_stateid_locked(struct nfs4_ol_stateid *stp,
>>>> }
>>>> 
>>>> idr_remove(&clp->cl_stateids, s->sc_stateid.si_opaque.so_id);
>>>> + nfs4_unhash_stid(s);
>>>> list_add(&stp->st_locks, reaplist);
>>>> }
>>>> 
>>>> @@ -1680,6 +1684,53 @@ static void release_openowner(struct nfs4_openowner *oo)
>>>> nfs4_put_stateowner(&oo->oo_owner);
>>>> }
>>>> 
>>>> +static struct nfs4_stid *find_one_sb_stid(struct nfs4_client *clp,
>>>> +   struct super_block *sb,
>>>> +   unsigned short sc_types)
>>>> +{
>>>> + unsigned long id, tmp;
>>>> + struct nfs4_stid *stid;
>>>> +
>>>> + spin_lock(&clp->cl_lock);
>>>> + idr_for_each_entry_ul(&clp->cl_stateids, stid, tmp, id)
>>>> + if ((stid->sc_type & sc_types) &&
>>>> +     stid->sc_file->fi_inode->i_sb == sb) {
>>>> + refcount_inc(&stid->sc_count);
>>>> + break;
>>>> + }
>>>> + spin_unlock(&clp->cl_lock);
>>>> + return stid;
>>>> +}
>>>> +
>>>> +void nfsd4_revoke_states(struct net *net, struct super_block *sb)
>>>> +{
>>>> + struct nfsd_net *nn = net_generic(net, nfsd_net_id);
>>>> + unsigned int idhashval;
>>>> + unsigned short sc_types;
>>>> +
>>>> + sc_types = 0;
>>>> +
>>>> + spin_lock(&nn->client_lock);
>>>> + for (idhashval = 0; idhashval < CLIENT_HASH_MASK; idhashval++) {
>>>> + struct list_head *head = &nn->conf_id_hashtbl[idhashval];
>>>> + struct nfs4_client *clp;
>>>> + retry:
>>>> + list_for_each_entry(clp, head, cl_idhash) {
>>>> + struct nfs4_stid *stid = find_one_sb_stid(clp, sb,
>>>> +   sc_types);
>>>> + if (stid) {
>>>> + spin_unlock(&nn->client_lock);
>>>> + switch (stid->sc_type) {
>>>> + }
>>>> + nfs4_put_stid(stid);
>>>> + spin_lock(&nn->client_lock);
>>>> + goto retry;
>>>> + }
>>>> + }
>>>> + }
>>>> + spin_unlock(&nn->client_lock);
>>>> +}
>>>> +
>>>> static inline int
>>>> hash_sessionid(struct nfs4_sessionid *sessionid)
>>>> {
>>>> @@ -2465,7 +2516,8 @@ find_stateid_locked(struct nfs4_client *cl, stateid_t *t)
>>>> }
>>>> 
>>>> static struct nfs4_stid *
>>>> -find_stateid_by_type(struct nfs4_client *cl, stateid_t *t, char typemask)
>>>> +find_stateid_by_type(struct nfs4_client *cl, stateid_t *t,
>>>> +      unsigned short typemask)
>>>> {
>>>> struct nfs4_stid *s;
>>>> 
>>>> @@ -2549,6 +2601,8 @@ static int client_info_show(struct seq_file *m, void *v)
>>>> }
>>>> seq_printf(m, "callback state: %s\n", cb_state2str(clp->cl_cb_state));
>>>> seq_printf(m, "callback address: %pISpc\n", &clp->cl_cb_conn.cb_addr);
>>>> + seq_printf(m, "admin-revoked states: %d\n",
>>>> +    atomic_read(&clp->cl_admin_revoked));
>>>> drop_client(clp);
>>>> 
>>>> return 0;
>>>> @@ -4108,6 +4162,8 @@ nfsd4_sequence(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
>>>> }
>>>> if (!list_empty(&clp->cl_revoked))
>>>> seq->status_flags |= SEQ4_STATUS_RECALLABLE_STATE_REVOKED;
>>>> + if (atomic_read(&clp->cl_admin_revoked))
>>>> + seq->status_flags |= SEQ4_STATUS_ADMIN_STATE_REVOKED;
>>>> out_no_session:
>>>> if (conn)
>>>> free_conn(conn);
>>>> @@ -5200,6 +5256,11 @@ nfs4_check_deleg(struct nfs4_client *cl, struct nfsd4_open *open,
>>>> status = nfserr_deleg_revoked;
>>>> goto out;
>>>> }
>>>> + if (deleg->dl_stid.sc_type == NFS4_ADMIN_REVOKED_DELEG_STID) {
>>>> + nfs4_put_stid(&deleg->dl_stid);
>>>> + status = nfserr_admin_revoked;
>>>> + goto out;
>>>> + }
>>>> flags = share_access_to_flags(open->op_share_access);
>>>> status = nfs4_check_delegmode(deleg, flags);
>>>> if (status) {
>>>> @@ -6478,6 +6539,11 @@ static __be32 nfsd4_validate_stateid(struct nfs4_client *cl, stateid_t *stateid)
>>>> case NFS4_REVOKED_DELEG_STID:
>>>> status = nfserr_deleg_revoked;
>>>> break;
>>>> + case NFS4_ADMIN_REVOKED_STID:
>>>> + case NFS4_ADMIN_REVOKED_LOCK_STID:
>>>> + case NFS4_ADMIN_REVOKED_DELEG_STID:
>>>> + status = nfserr_admin_revoked;
>>>> + break;
>>>> case NFS4_OPEN_STID:
>>>> case NFS4_LOCK_STID:
>>>> status = nfsd4_check_openowner_confirmed(openlockstateid(s));
>>>> @@ -6496,7 +6562,7 @@ static __be32 nfsd4_validate_stateid(struct nfs4_client *cl, stateid_t *stateid)
>>>> 
>>>> __be32
>>>> nfsd4_lookup_stateid(struct nfsd4_compound_state *cstate,
>>>> -      stateid_t *stateid, unsigned char typemask,
>>>> +      stateid_t *stateid, unsigned short typemask,
>>>>      struct nfs4_stid **s, struct nfsd_net *nn)
>>>> {
>>>> __be32 status;
>>>> @@ -6512,6 +6578,13 @@ nfsd4_lookup_stateid(struct nfsd4_compound_state *cstate,
>>>> else if (typemask & NFS4_DELEG_STID)
>>>> typemask |= NFS4_REVOKED_DELEG_STID;
>>>> 
>>>> + if (typemask & NFS4_OPEN_STID)
>>>> + typemask |= NFS4_ADMIN_REVOKED_STID;
>>>> + if (typemask & NFS4_LOCK_STID)
>>>> + typemask |= NFS4_ADMIN_REVOKED_LOCK_STID;
>>>> + if (typemask & NFS4_DELEG_STID)
>>>> + typemask |= NFS4_ADMIN_REVOKED_DELEG_STID;
>>>> +
>>>> if (ZERO_STATEID(stateid) || ONE_STATEID(stateid) ||
>>>> CLOSE_STATEID(stateid))
>>>> return nfserr_bad_stateid;
>>>> @@ -6532,6 +6605,10 @@ nfsd4_lookup_stateid(struct nfsd4_compound_state *cstate,
>>>> return nfserr_deleg_revoked;
>>>> return nfserr_bad_stateid;
>>>> }
>>>> + if (stid->sc_type & NFS4_ALL_ADMIN_REVOKED_STIDS) {
>>>> + nfs4_put_stid(stid);
>>>> + return nfserr_admin_revoked;
>>>> + }
>>>> *s = stid;
>>>> return nfs_ok;
>>>> }
>>>> @@ -6899,7 +6976,7 @@ static __be32 nfs4_seqid_op_checks(struct nfsd4_compound_state *cstate, stateid_
>>>>  */
>>>> static __be32
>>>> nfs4_preprocess_seqid_op(struct nfsd4_compound_state *cstate, u32 seqid,
>>>> -  stateid_t *stateid, char typemask,
>>>> +  stateid_t *stateid, unsigned short typemask,
>>>>  struct nfs4_ol_stateid **stpp,
>>>>  struct nfsd_net *nn)
>>>> {
>>>> diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
>>>> index 739ed5bf71cd..50368eec86b0 100644
>>>> --- a/fs/nfsd/nfsctl.c
>>>> +++ b/fs/nfsd/nfsctl.c
>>>> @@ -281,6 +281,7 @@ static ssize_t write_unlock_fs(struct file *file, char *buf, size_t size)
>>>>  * 3.  Is that directory the root of an exported file system?
>>>>  */
>>>> error = nlmsvc_unlock_all_by_sb(path.dentry->d_sb);
>>>> + nfsd4_revoke_states(netns(file), path.dentry->d_sb);
>>>> 
>>>> path_put(&path);
>>>> return error;
>>>> diff --git a/fs/nfsd/nfsd.h b/fs/nfsd/nfsd.h
>>>> index f5ff42f41ee7..d46203eac3c8 100644
>>>> --- a/fs/nfsd/nfsd.h
>>>> +++ b/fs/nfsd/nfsd.h
>>>> @@ -280,6 +280,7 @@ void nfsd_lockd_shutdown(void);
>>>> #define nfserr_no_grace cpu_to_be32(NFSERR_NO_GRACE)
>>>> #define nfserr_reclaim_bad cpu_to_be32(NFSERR_RECLAIM_BAD)
>>>> #define nfserr_badname cpu_to_be32(NFSERR_BADNAME)
>>>> +#define nfserr_admin_revoked cpu_to_be32(NFS4ERR_ADMIN_REVOKED)
>>>> #define nfserr_cb_path_down cpu_to_be32(NFSERR_CB_PATH_DOWN)
>>>> #define nfserr_locked cpu_to_be32(NFSERR_LOCKED)
>>>> #define nfserr_wrongsec cpu_to_be32(NFSERR_WRONGSEC)
>>>> diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h
>>>> index f96eaa8e9413..3af5ab55c978 100644
>>>> --- a/fs/nfsd/state.h
>>>> +++ b/fs/nfsd/state.h
>>>> @@ -88,17 +88,23 @@ struct nfsd4_callback_ops {
>>>>  */
>>>> struct nfs4_stid {
>>>> refcount_t sc_count;
>>>> -#define NFS4_OPEN_STID 1
>>>> -#define NFS4_LOCK_STID 2
>>>> -#define NFS4_DELEG_STID 4
>>>> + struct list_head sc_cp_list;
>>>> + unsigned short sc_type;
>>> 
>>> Should we just go ahead and make this a full 32-bit word? We seem to
>>> keep adding flags to this field, and I doubt we're saving anything by
>>> making this a short.
>>> 
>>>> +#define NFS4_OPEN_STID BIT(0)
>>>> +#define NFS4_LOCK_STID BIT(1)
>>>> +#define NFS4_DELEG_STID BIT(2)
>>>> /* For an open stateid kept around *only* to process close replays: */
>>>> -#define NFS4_CLOSED_STID 8
>>>> +#define NFS4_CLOSED_STID BIT(3)
>>>> /* For a deleg stateid kept around only to process free_stateid's: */
>>>> -#define NFS4_REVOKED_DELEG_STID 16
>>>> -#define NFS4_CLOSED_DELEG_STID 32
>>>> -#define NFS4_LAYOUT_STID 64
>>>> - struct list_head sc_cp_list;
>>>> - unsigned char sc_type;
>>>> +#define NFS4_REVOKED_DELEG_STID BIT(4)
>>>> +#define NFS4_CLOSED_DELEG_STID BIT(5)
>>>> +#define NFS4_LAYOUT_STID BIT(6)
>>>> +#define NFS4_ADMIN_REVOKED_STID BIT(7)
>>>> +#define NFS4_ADMIN_REVOKED_LOCK_STID BIT(8)
>>>> +#define NFS4_ADMIN_REVOKED_DELEG_STID BIT(9)
>>>> +#define NFS4_ALL_ADMIN_REVOKED_STIDS (NFS4_ADMIN_REVOKED_STID | \
>>>> +      NFS4_ADMIN_REVOKED_LOCK_STID | \
>>>> +      NFS4_ADMIN_REVOKED_DELEG_STID)
>>> 
>>> Not a specific criticism of these patches, since this problem preexists
>>> them, but I really dislike the way that sc_type is used as a bitmask,
>>> but also sort of like an enum. In some cases, we test for specific flags
>>> in the mask, and in other cases (e.g. states_show), we treat them as
>>> discrete values to feed it to a switch().
>>> 
>>> Personally, I'd find this less confusing if we just treat this as a set
>>> of flags full-stop. We could leave the low-order bits to show the real
>>> type (open, lock, deleg, etc.) and just mask off the high-order bits
>>> when we need to feed it to a switch statement.
>>> 
>>> For instance above, we're adding 3 new NFS4_ADMIN_REVOKED values, but we
>>> could (in theory) just have a flag in there that says NFS4_ADMIN_REVOKED
>>> and leave the old type bit in place instead of changing it to a new
>>> discrete sc_type value.
>> 
>> I agree.
>> Bits might be:
>>    OPEN
>>    LOCK
>>    DELEG
>>    LAYOUT
>>    CLOSED (combines with OPEN or DELEG)
>>    REVOKED (combines with DELEG)
>>    ADMIN_REVOKED (combined with OPEN, LOCK, DELEG.  Sets REVOKED when
>>                   with DELEG)
>> 
>> so we could go back to a char :-)  Probably sensible to use unsigned int
>> though.
>> 
> 
> Yeah, a u32 would be best I think. It'll just fill an existing hole on
> my box (x86_64), according to pahole:
> 
> unsigned char              sc_type;              /*    24     1 */
> 
> /* XXX 3 bytes hole, try to pack */
> 
>> For updates the rule would be that bits can be set but never cleared so
>> you don't need locking to read unless you care about a bit that can be
>> changed.
>> 
> 
> Probably for the low order OPEN/LOCK/DELEG bits, the rule should be that
> they never change. We can never convert from one to another since they
> come out of different slabcaches. It's probably worthwhile to leave a
> few low order bits carved out for new types in the future too. e.g.
> directory delegations...
> 
> Maybe we should rename the field too? How about "sc_mode" since this is
> starting to resemble the i_mode field in some ways (type and permissions
> squashed together).

In that case, two separate u16 fields might be better.


--
Chuck Lever