On Mon, 2016-08-08 at 15:53 -0400, J. Bruce Fields wrote:
> On Mon, Aug 08, 2016 at 12:14:36PM -0400, Chuck Lever wrote:
> >
> >
> > >
> > > On Aug 8, 2016, at 9:19 AM, Jeff Layton <jlayton@xxxxxxxxxx>
> > > wrote:
> > >
> > > On Sun, 2016-08-07 at 18:22 -0400, Jeff Layton wrote:
> > > >
> > > > On Sun, 2016-08-07 at 14:53 -0400, Chuck Lever wrote:
> > > > >
> > > > >
> > > > > When running LTP's nfslock01 test, the Linux client can send
> > > > > a LOCK
> > > > > and a FREE_STATEID request at the same time. The LOCK uses
> > > > > the same
> > > > > lockowner as the stateid sent in the FREE_STATEID request.
> > > > >
> > > > > The outcome is:
> > > > >
> > > > > Frame 115025 C FREE_STATEID stateid 2/A
> > > > > Frame 115026 C LOCK offset 672128 len 64
> > > > > Frame 115029 R FREE_STATEID NFS4_OK
> > > > > Frame 115030 R LOCK stateid 3/A
> > >
> > > Oh, to be clear here -- I assume this a lk_is_new lock (with an
> > > open
> > > stateid in it). Right?
> >
> > Opcode: LOCK (12)
> > locktype: WRITEW_LT (4)
> > reclaim?: No
> > offset: 672000
> > length: 64
> > new lock owner?: Yes
> > seqid: 0x00000000
> > stateid
> > [StateID Hash: 0x6f7e]
> > seqid: 0x00000002
> > Data: a95169579501000007000000
> > lock_seqid: 0x00000000
> > Owner
> > clientid: 0xa951695795010000
> > Data: <DATA>
> > length: 20
> > contents: <DATA>
> >
> > The first appearance of that stateid is in an earlier OPEN reply:
> >
> > Opcode: OPEN (18)
> > Status: NFS4_OK (0)
> > stateid
> > [StateID Hash: 0x6f7e]
> > seqid: 0x00000002
> > Data: a95169579501000007000000
> > change_info
> > Atomic: No
> > changeid (before): 0
> > changeid (after): 0
> > result flags: 0x00000004, locktype posix
> > .... .... .... .... .... .... .... ..0. = confirm:
> > False
> > .... .... .... .... .... .... .... .1.. = locktype
> > posix: True
> > .... .... .... .... .... .... .... 0... = preserve
> > unlinked: False
> > .... .... .... .... .... .... ..0. .... = may
> > notify lock: False
> > Delegation Type: OPEN_DELEGATE_NONE (0)
>
> Oh, the client behavior makes more sense, then.
>
> Still, did we establish for certain that the client isn't required to
> serialize here?
>
> We'd want it fixed either way, but it'd be nice to know.
>
> --b.
>
I don't _think_ it is, since we aren't using a LOCK stateid at this
point. There's really nothing to serialize this against, other than
pending FREE_STATEID calls. I don't think we'd want to serialize LOCK
and FREE_STATEID though as that would prevent the client from lazily
freeing them. I think this is probably a better option.
> >
> >
> > >
> > > >
> > > > >
> > > > > Frame 115034 C WRITE stateid 0/A offset 672128 len 64
> > > > > Frame 115038 R WRITE NFS4ERR_BAD_STATEID
> > > > >
> > > > > In other words, the server returns stateid A in a successful
> > > > > LOCK
> > > > > reply, but it has already released it. Subsequent uses of the
> > > > > stateid fail.
> > > > >
> > > > > To address this, protect the generation check in
> > > > > nfsd4_free_stateid
> > > > > with the st_mutex. This should guarantee that only one of two
> > > > > outcomes occurs: either LOCK returns a fresh valid stateid,
> > > > > or
> > > > > FREE_STATEID returns NFS4ERR_LOCKS_HELD.
> > > > >
> > > > > Reported-by: Alexey Kodanev <alexey.kodanev@xxxxxxxxxx>
> > > > > Fix-suggested-by: Jeff Layton <jlayton@xxxxxxxxxx>
> > > > > Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
> > > > > ---
> > > > > fs/nfsd/nfs4state.c | 19 ++++++++++++-------
> > > > > 1 file changed, 12 insertions(+), 7 deletions(-)
> > > > >
> > > > > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> > > > > index b921123..07dc1aa 100644
> > > > > --- a/fs/nfsd/nfs4state.c
> > > > > +++ b/fs/nfsd/nfs4state.c
> > > > > @@ -4911,19 +4911,20 @@ nfsd4_free_stateid(struct svc_rqst
> > > > > *rqstp,
> > > > > struct nfsd4_compound_state *cstate,
> > > > > ret = nfserr_locks_held;
> > > > > break;
> > > > > case NFS4_LOCK_STID:
> > > > > + atomic_inc(&s->sc_count);
> > > > > + spin_unlock(&cl->cl_lock);
> > > > > + stp = openlockstateid(s);
> > > > > + mutex_lock(&stp->st_mutex);
> > > > > ret = check_stateid_generation(stateid, &s-
> > > > > >
> > > > > >
> > > > > > sc_stateid, 1);
> > > > > if (ret)
> > > > > - break;
> > > > > - stp = openlockstateid(s);
> > > > > + goto out_mutex_unlock;
> > > > > ret = nfserr_locks_held;
> > > > > if (check_for_locks(stp->st_stid.sc_file,
> > > > > lockowner(stp-
> > > > > >
> > > > > > st_stateowner)))
> > > > > - break;
> > > > > - WARN_ON(!unhash_lock_stateid(stp));
> > > > > - spin_unlock(&cl->cl_lock);
> > > > > - nfs4_put_stid(s);
> > > > > + goto out_mutex_unlock;
> > > > > + release_lock_stateid(stp);
> > > > > ret = nfs_ok;
> > > > > - goto out;
> > > > > + goto out_mutex_unlock;
> > > > > case NFS4_REVOKED_DELEG_STID:
> > > > > dp = delegstateid(s);
> > > > > list_del_init(&dp->dl_recall_lru);
> > > > > @@ -4937,6 +4938,10 @@ out_unlock:
> > > > > spin_unlock(&cl->cl_lock);
> > > > > out:
> > > > > return ret;
> > > > > +out_mutex_unlock:
> > > > > + mutex_unlock(&stp->st_mutex);
> > > > > + nfs4_put_stid(s);
> > > > > + goto out;
> > > > > }
> > > > >
> > > > > static inline int
> > > > >
> > > > >
> > > >
> > > > Looks good to me.
> > > >
> > > > Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
> > >
> > > Hmm...I think this is not a complete fix though. We also need
> > > something
> > > like this patch:
> >
> > OK, I'll create a series and add this patch.
> >
> >
> > >
> > > --------------[snip]---------------
> > >
> > > [PATCH] nfsd: don't return an already-unhashed lock stateid after
> > > taking mutex
> > >
> > > nfsd4_lock will take the st_mutex before working with the stateid
> > > it
> > > gets, but between the time when we drop the cl_lock and take the
> > > mutex,
> > > the stateid could become unhashed (a'la FREE_STATEID). If that
> > > happens
> > > the lock stateid returned to the client will be forgotten.
> > >
> > > Fix this by first moving the st_mutex acquisition into
> > > lookup_or_create_lock_state. Then, have it check to see if the
> > > lock
> > > stateid is still hashed after taking the mutex. If it's not, then
> > > put
> > > the stateid and try the find/create again.
> > >
> > > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
> > > ---
> > > fs/nfsd/nfs4state.c | 25 ++++++++++++++++++++-----
> > > 1 file changed, 20 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> > > index 5d6a28af0f42..1235b1661703 100644
> > > --- a/fs/nfsd/nfs4state.c
> > > +++ b/fs/nfsd/nfs4state.c
> > > @@ -5653,7 +5653,7 @@ static __be32
> > > lookup_or_create_lock_state(struct nfsd4_compound_state *cstate,
> > > struct nfs4_ol_stateid *ost,
> > > struct nfsd4_lock *lock,
> > > - struct nfs4_ol_stateid **lst, bool
> > > *new)
> > > + struct nfs4_ol_stateid **plst, bool
> > > *new)
> > > {
> > > __be32 status;
> > > struct nfs4_file *fi = ost->st_stid.sc_file;
> > > @@ -5661,7 +5661,9 @@ lookup_or_create_lock_state(struct
> > > nfsd4_compound_state *cstate,
> > > struct nfs4_client *cl = oo->oo_owner.so_client;
> > > struct inode *inode = d_inode(cstate->current_fh.fh_dentry);
> > > struct nfs4_lockowner *lo;
> > > + struct nfs4_ol_stateid *lst;
> > > unsigned int strhashval;
> > > + bool hashed;
> > >
> > > lo = find_lockowner_str(cl, &lock->lk_new_owner);
> > > if (!lo) {
> > > @@ -5677,12 +5679,27 @@ lookup_or_create_lock_state(struct
> > > nfsd4_compound_state *cstate,
> > > goto out;
> > > }
> > >
> > > - *lst = find_or_create_lock_stateid(lo, fi, inode, ost,
> > > new);
> > > - if (*lst == NULL) {
> > > +retry:
> > > + lst = find_or_create_lock_stateid(lo, fi, inode, ost,
> > > new);
> > > + if (lst == NULL) {
> > > status = nfserr_jukebox;
> > > goto out;
> > > }
> > > +
> > > + mutex_lock(&lst->st_mutex);
> > > +
> > > + /* See if it's still hashed to avoid race with
> > > FREE_STATEID */
> > > + spin_lock(&cl->cl_lock);
> > > + hashed = list_empty(&lst->st_perfile);
> > > + spin_unlock(&cl->cl_lock);
> > > +
> > > + if (!hashed) {
> > > + mutex_unlock(&lst->st_mutex);
> > > + nfs4_put_stid(&lst->st_stid);
> > > + goto retry;
> > > + }
> > > status = nfs_ok;
> > > + *plst = lst;
> > > out:
> > > nfs4_put_stateowner(&lo->lo_owner);
> > > return status;
> > > @@ -5752,8 +5769,6 @@ nfsd4_lock(struct svc_rqst *rqstp, struct
> > > nfsd4_compound_state *cstate,
> > > goto out;
> > > status = lookup_or_create_lock_state(cstate, open_stp,
> > > lock,
> > > &lock_stp,
> > > &new);
> > > - if (status == nfs_ok)
> > > - mutex_lock(&lock_stp->st_mutex);
> > > } else {
> > > status = nfs4_preprocess_seqid_op(cstate,
> > > lock->lk_old_lock_seqid,
> > > --
> > > 2.7.4
> >
> > --
> > Chuck Lever
> >
> >
> >
> > --
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--
Jeff Layton <jlayton@xxxxxxxxxx>
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