Re: [PATCH 13/13] nfsd: allow layout state to be admin-revoked.

[Jeff Layton <jlayton@kernel.org>]

On Wed, 2024-01-31 at 09:13 +1100, NeilBrown wrote:
> On Tue, 30 Jan 2024, Jeff Layton wrote:
> > On Tue, 2024-01-30 at 12:08 +1100, NeilBrown wrote:
> > > When there is layout state on a filesystem that is being "unlocked" that
> > > is now revoked, which involves closing the nfsd_file and releasing the
> > > vfs lease.
> > > 
> > > To avoid races, ->ls_file can now be accessed either:
> > >  - under ->fi_lock for the state's sc_file or
> > >  - under rcu_read_lock() if nfsd_file_get() is used.
> > > To support this, ->fence_client and nfsd4_cb_layout_fail() now take a
> > > second argument being the nfsd_file.
> > > 
> > > Signed-off-by: NeilBrown <neilb@suse.de>
> > > ---
> > >  fs/nfsd/blocklayout.c |  4 ++--
> > >  fs/nfsd/nfs4layouts.c | 43 ++++++++++++++++++++++++++++++++-----------
> > >  fs/nfsd/nfs4state.c   | 11 +++++++++--
> > >  fs/nfsd/pnfs.h        |  8 +++++++-
> > >  4 files changed, 50 insertions(+), 16 deletions(-)
> > > 
> > > diff --git a/fs/nfsd/blocklayout.c b/fs/nfsd/blocklayout.c
> > > index 46fd74d91ea9..3c040c81c77d 100644
> > > --- a/fs/nfsd/blocklayout.c
> > > +++ b/fs/nfsd/blocklayout.c
> > > @@ -328,10 +328,10 @@ nfsd4_scsi_proc_layoutcommit(struct inode *inode,
> > >  }
> > >  
> > >  static void
> > > -nfsd4_scsi_fence_client(struct nfs4_layout_stateid *ls)
> > > +nfsd4_scsi_fence_client(struct nfs4_layout_stateid *ls, struct nfsd_file *file)
> > >  {
> > >  	struct nfs4_client *clp = ls->ls_stid.sc_client;
> > > -	struct block_device *bdev = ls->ls_file->nf_file->f_path.mnt->mnt_sb->s_bdev;
> > > +	struct block_device *bdev = file->nf_file->f_path.mnt->mnt_sb->s_bdev;
> > >  
> > >  	bdev->bd_disk->fops->pr_ops->pr_preempt(bdev, NFSD_MDS_PR_KEY,
> > >  			nfsd4_scsi_pr_key(clp), 0, true);
> > > diff --git a/fs/nfsd/nfs4layouts.c b/fs/nfsd/nfs4layouts.c
> > > index 857b822450b4..1cfd61db2472 100644
> > > --- a/fs/nfsd/nfs4layouts.c
> > > +++ b/fs/nfsd/nfs4layouts.c
> > > @@ -152,6 +152,23 @@ void nfsd4_setup_layout_type(struct svc_export *exp)
> > >  #endif
> > >  }
> > >  
> > > +void nfsd4_close_layout(struct nfs4_layout_stateid *ls)
> > > +{
> > > +	struct nfsd_file *fl;
> > > +
> > > +	spin_lock(&ls->ls_stid.sc_file->fi_lock);
> > > +	fl = ls->ls_file;
> > > +	ls->ls_file = NULL;
> > > +	spin_unlock(&ls->ls_stid.sc_file->fi_lock);
> > > +
> > > +	if (fl) {
> > > +		if (!nfsd4_layout_ops[ls->ls_layout_type]->disable_recalls)
> > > +			vfs_setlease(fl->nf_file, F_UNLCK, NULL,
> > > +				     (void **)&ls);
> > > +		nfsd_file_put(fl);
> > > +	}
> > > +}
> > > +
> > >  static void
> > >  nfsd4_free_layout_stateid(struct nfs4_stid *stid)
> > >  {
> > > @@ -169,9 +186,7 @@ nfsd4_free_layout_stateid(struct nfs4_stid *stid)
> > >  	list_del_init(&ls->ls_perfile);
> > >  	spin_unlock(&fp->fi_lock);
> > >  
> > > -	if (!nfsd4_layout_ops[ls->ls_layout_type]->disable_recalls)
> > > -		vfs_setlease(ls->ls_file->nf_file, F_UNLCK, NULL, (void **)&ls);
> > > -	nfsd_file_put(ls->ls_file);
> > > +	nfsd4_close_layout(ls);
> > >  
> > >  	if (ls->ls_recalled)
> > >  		atomic_dec(&ls->ls_stid.sc_file->fi_lo_recalls);
> > > @@ -605,7 +620,7 @@ nfsd4_return_all_file_layouts(struct nfs4_client *clp, struct nfs4_file *fp)
> > >  }
> > >  
> > >  static void
> > > -nfsd4_cb_layout_fail(struct nfs4_layout_stateid *ls)
> > > +nfsd4_cb_layout_fail(struct nfs4_layout_stateid *ls, struct nfsd_file *file)
> > >  {
> > >  	struct nfs4_client *clp = ls->ls_stid.sc_client;
> > >  	char addr_str[INET6_ADDRSTRLEN];
> > > @@ -627,7 +642,7 @@ nfsd4_cb_layout_fail(struct nfs4_layout_stateid *ls)
> > >  
> > >  	argv[0] = (char *)nfsd_recall_failed;
> > >  	argv[1] = addr_str;
> > > -	argv[2] = ls->ls_file->nf_file->f_path.mnt->mnt_sb->s_id;
> > > +	argv[2] = file->nf_file->f_path.mnt->mnt_sb->s_id;
> > >  	argv[3] = NULL;
> > >  
> > >  	error = call_usermodehelper(nfsd_recall_failed, argv, envp,
> > > @@ -657,6 +672,7 @@ nfsd4_cb_layout_done(struct nfsd4_callback *cb, struct rpc_task *task)
> > >  	struct nfsd_net *nn;
> > >  	ktime_t now, cutoff;
> > >  	const struct nfsd4_layout_ops *ops;
> > > +	struct nfsd_file *fl;
> > >  
> > >  	trace_nfsd_cb_layout_done(&ls->ls_stid.sc_stateid, task);
> > >  	switch (task->tk_status) {
> > > @@ -688,12 +704,17 @@ nfsd4_cb_layout_done(struct nfsd4_callback *cb, struct rpc_task *task)
> > >  		 * Unknown error or non-responding client, we'll need to fence.
> > >  		 */
> > >  		trace_nfsd_layout_recall_fail(&ls->ls_stid.sc_stateid);
> > > -
> > > -		ops = nfsd4_layout_ops[ls->ls_layout_type];
> > > -		if (ops->fence_client)
> > > -			ops->fence_client(ls);
> > > -		else
> > > -			nfsd4_cb_layout_fail(ls);
> > > +		rcu_read_lock();
> > > +		fl = nfsd_file_get(ls->ls_file);
> > > +		rcu_read_unlock();
> > 
> > I'm still wondering about the rcu_read_lock above. It's probably
> > harmless, but it seems unnecessary since you already hold a reference to
> > "ls". Is there a reason for it?
> 
> I replied !
> 
> https://lore.kernel.org/linux-nfs/170657686307.21664.13889535187781187364@noble.neil.brown.name/
> 
> See nfsd4_close_layout().  A ref on ls doesn't guarantee a ref on
> ls->ls_file any more.
> 
> 

Hmmm... I never received that reply.

The answer makes sense though, thanks. You can add my Reviewed-by to
13/13 as well.

Cheers,

> > 
> > > +		if (fl) {
> > > +			ops = nfsd4_layout_ops[ls->ls_layout_type];
> > > +			if (ops->fence_client)
> > > +				ops->fence_client(ls, fl);
> > > +			else
> > > +				nfsd4_cb_layout_fail(ls, fl);
> > > +			nfsd_file_put(fl);
> > > +		}
> > >  		return 1;
> > >  	case -NFS4ERR_NOMATCHING_LAYOUT:
> > >  		trace_nfsd_layout_recall_done(&ls->ls_stid.sc_stateid);
> > > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> > > index fe21af8dfc68..a66d66b9f769 100644
> > > --- a/fs/nfsd/nfs4state.c
> > > +++ b/fs/nfsd/nfs4state.c
> > > @@ -1721,7 +1721,7 @@ void nfsd4_revoke_states(struct net *net, struct super_block *sb)
> > >  	unsigned int idhashval;
> > >  	unsigned int sc_types;
> > >  
> > > -	sc_types = SC_TYPE_OPEN | SC_TYPE_LOCK | SC_TYPE_DELEG;
> > > +	sc_types = SC_TYPE_OPEN | SC_TYPE_LOCK | SC_TYPE_DELEG | SC_TYPE_LAYOUT;
> > >  
> > >  	spin_lock(&nn->client_lock);
> > >  	for (idhashval = 0; idhashval < CLIENT_HASH_MASK; idhashval++) {
> > > @@ -1734,6 +1734,7 @@ void nfsd4_revoke_states(struct net *net, struct super_block *sb)
> > >  			if (stid) {
> > >  				struct nfs4_ol_stateid *stp;
> > >  				struct nfs4_delegation *dp;
> > > +				struct nfs4_layout_stateid *ls;
> > >  
> > >  				spin_unlock(&nn->client_lock);
> > >  				switch (stid->sc_type) {
> > > @@ -1789,6 +1790,10 @@ void nfsd4_revoke_states(struct net *net, struct super_block *sb)
> > >  					if (dp)
> > >  						revoke_delegation(dp);
> > >  					break;
> > > +				case SC_TYPE_LAYOUT:
> > > +					ls = layoutstateid(stid);
> > > +					nfsd4_close_layout(ls);
> > > +					break;
> > >  				}
> > >  				nfs4_put_stid(stid);
> > >  				spin_lock(&nn->client_lock);
> > > @@ -2868,7 +2873,6 @@ static int nfs4_show_layout(struct seq_file *s, struct nfs4_stid *st)
> > >  	struct nfsd_file *file;
> > >  
> > >  	ls = container_of(st, struct nfs4_layout_stateid, ls_stid);
> > > -	file = ls->ls_file;
> > >  
> > >  	seq_puts(s, "- ");
> > >  	nfs4_show_stateid(s, &st->sc_stateid);
> > > @@ -2876,12 +2880,15 @@ static int nfs4_show_layout(struct seq_file *s, struct nfs4_stid *st)
> > >  
> > >  	/* XXX: What else would be useful? */
> > >  
> > > +	spin_lock(&ls->ls_stid.sc_file->fi_lock);
> > > +	file = ls->ls_file;
> > >  	if (file) {
> > >  		seq_puts(s, ", ");
> > >  		nfs4_show_superblock(s, file);
> > >  		seq_puts(s, ", ");
> > >  		nfs4_show_fname(s, file);
> > >  	}
> > > +	spin_unlock(&ls->ls_stid.sc_file->fi_lock);
> > >  	if (st->sc_status & SC_STATUS_ADMIN_REVOKED)
> > >  		seq_puts(s, ", admin-revoked");
> > >  	seq_puts(s, " }\n");
> > > diff --git a/fs/nfsd/pnfs.h b/fs/nfsd/pnfs.h
> > > index de1e0dfed06a..925817f66917 100644
> > > --- a/fs/nfsd/pnfs.h
> > > +++ b/fs/nfsd/pnfs.h
> > > @@ -37,7 +37,8 @@ struct nfsd4_layout_ops {
> > >  	__be32 (*proc_layoutcommit)(struct inode *inode,
> > >  			struct nfsd4_layoutcommit *lcp);
> > >  
> > > -	void (*fence_client)(struct nfs4_layout_stateid *ls);
> > > +	void (*fence_client)(struct nfs4_layout_stateid *ls,
> > > +			     struct nfsd_file *file);
> > >  };
> > >  
> > >  extern const struct nfsd4_layout_ops *nfsd4_layout_ops[];
> > > @@ -72,11 +73,13 @@ void nfsd4_setup_layout_type(struct svc_export *exp);
> > >  void nfsd4_return_all_client_layouts(struct nfs4_client *);
> > >  void nfsd4_return_all_file_layouts(struct nfs4_client *clp,
> > >  		struct nfs4_file *fp);
> > > +void nfsd4_close_layout(struct nfs4_layout_stateid *ls);
> > >  int nfsd4_init_pnfs(void);
> > >  void nfsd4_exit_pnfs(void);
> > >  #else
> > >  struct nfs4_client;
> > >  struct nfs4_file;
> > > +struct nfs4_layout_stateid;
> > >  
> > >  static inline void nfsd4_setup_layout_type(struct svc_export *exp)
> > >  {
> > > @@ -89,6 +92,9 @@ static inline void nfsd4_return_all_file_layouts(struct nfs4_client *clp,
> > >  		struct nfs4_file *fp)
> > >  {
> > >  }
> > > +static inline void nfsd4_close_layout(struct nfs4_layout_stateid *ls)
> > > +{
> > > +}
> > >  static inline void nfsd4_exit_pnfs(void)
> > >  {
> > >  }
> > 
> > -- 
> > Jeff Layton <jlayton@kernel.org>
> > 
> > 
> 

-- 
Jeff Layton <jlayton@kernel.org>