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Message-ID: <b1b3e12dc335dcadbf038e87a33529e0fe711230.camel@kernel.org>
Subject: Re: [PATCH 1/4  v3] nfsd: perform all find_openstateowner_str calls
 in the one place.
From: Jeff Layton <jlayton@kernel.org>
To: NeilBrown <neilb@suse.de>, Chuck Lever <chuck.lever@oracle.com>
Cc: linux-nfs@vger.kernel.org, Olga Kornievskaia <kolga@netapp.com>, Dai Ngo
	 <Dai.Ngo@oracle.com>, Tom Talpey <tom@talpey.com>
Date: Mon, 11 Mar 2024 07:34:22 -0400
In-Reply-To: <171010907730.13576.5751778995820664441@noble.neil.brown.name>
References: <171010907730.13576.5751778995820664441@noble.neil.brown.name>
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On Mon, 2024-03-11 at 09:17 +1100, NeilBrown wrote:
> Currently find_openstateowner_str lookups are done both in
> nfsd4_process_open1() and alloc_init_open_stateowner() - the latter
> possibly being a surprise based on its name.
>=20
> It would be easier to follow, and more conformant to common patterns, if
> the lookup was all in the one place.
>=20
> So replace alloc_init_open_stateowner() with
> find_or_alloc_open_stateowner() and use the latter in
> nfsd4_process_open1() without any calls to find_openstateowner_str().
>=20
> This means all finds are find_openstateowner_str_locked() and
> find_openstateowner_str() is no longer needed.  So discard
> find_openstateowner_str() and rename find_openstateowner_str_locked() to
> find_openstateowner_str().
>=20
> Signed-off-by: NeilBrown <neilb@suse.de>
> ---
>=20
> The previous version of this patch could deadlock on ->cl_lcok as it
> called release_openowner() while holding that lock.
> This version doesn't.
>=20
> Subsequent patch in the original series should be unchanged.  If needed
> I can resent them all after -rc1 is out.
>=20
>  fs/nfsd/nfs4state.c | 93 +++++++++++++++++++--------------------------
>  1 file changed, 40 insertions(+), 53 deletions(-)
>=20
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index ee9aa4843443..3e144b1a1386 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -541,7 +541,7 @@ same_owner_str(struct nfs4_stateowner *sop, struct xd=
r_netobj *owner)
>  }
> =20
>  static struct nfs4_openowner *
> -find_openstateowner_str_locked(unsigned int hashval, struct nfsd4_open *=
open,
> +find_openstateowner_str(unsigned int hashval, struct nfsd4_open *open,
>  			struct nfs4_client *clp)
>  {
>  	struct nfs4_stateowner *so;
> @@ -558,18 +558,6 @@ find_openstateowner_str_locked(unsigned int hashval,=
 struct nfsd4_open *open,
>  	return NULL;
>  }
> =20
> -static struct nfs4_openowner *
> -find_openstateowner_str(unsigned int hashval, struct nfsd4_open *open,
> -			struct nfs4_client *clp)
> -{
> -	struct nfs4_openowner *oo;
> -
> -	spin_lock(&clp->cl_lock);
> -	oo =3D find_openstateowner_str_locked(hashval, open, clp);
> -	spin_unlock(&clp->cl_lock);
> -	return oo;
> -}
> -
>  static inline u32
>  opaque_hashval(const void *ptr, int nbytes)
>  {
> @@ -4855,34 +4843,46 @@ nfsd4_find_and_lock_existing_open(struct nfs4_fil=
e *fp, struct nfsd4_open *open)
>  }
> =20
>  static struct nfs4_openowner *
> -alloc_init_open_stateowner(unsigned int strhashval, struct nfsd4_open *o=
pen,
> -			   struct nfsd4_compound_state *cstate)
> +find_or_alloc_open_stateowner(unsigned int strhashval, struct nfsd4_open=
 *open,
> +			      struct nfsd4_compound_state *cstate)
>  {
>  	struct nfs4_client *clp =3D cstate->clp;
> -	struct nfs4_openowner *oo, *ret;
> +	struct nfs4_openowner *oo, *new =3D NULL;
> =20
> -	oo =3D alloc_stateowner(openowner_slab, &open->op_owner, clp);
> -	if (!oo)
> -		return NULL;
> -	oo->oo_owner.so_ops =3D &openowner_ops;
> -	oo->oo_owner.so_is_open_owner =3D 1;
> -	oo->oo_owner.so_seqid =3D open->op_seqid;
> -	oo->oo_flags =3D 0;
> -	if (nfsd4_has_session(cstate))
> -		oo->oo_flags |=3D NFS4_OO_CONFIRMED;
> -	oo->oo_time =3D 0;
> -	oo->oo_last_closed_stid =3D NULL;
> -	INIT_LIST_HEAD(&oo->oo_close_lru);
> +retry:
>  	spin_lock(&clp->cl_lock);
> -	ret =3D find_openstateowner_str_locked(strhashval, open, clp);
> -	if (ret =3D=3D NULL) {
> -		hash_openowner(oo, clp, strhashval);
> -		ret =3D oo;
> -	} else
> -		nfs4_free_stateowner(&oo->oo_owner);
> -
> +	oo =3D find_openstateowner_str(strhashval, open, clp);
> +	if (!oo && new) {
> +		hash_openowner(new, clp, strhashval);
> +		spin_unlock(&clp->cl_lock);
> +		return new;
> +	}
>  	spin_unlock(&clp->cl_lock);
> -	return ret;
> +
> +	if (oo && !(oo->oo_flags & NFS4_OO_CONFIRMED)) {
> +		/* Replace unconfirmed owners without checking for replay. */
> +		release_openowner(oo);
> +		oo =3D NULL;
> +	}
> +	if (oo) {
> +		if (new)
> +			nfs4_free_stateowner(&new->oo_owner);
> +		return oo;
> +	}
> +
> +	new =3D alloc_stateowner(openowner_slab, &open->op_owner, clp);
> +	if (!new)
> +		return NULL;
> +	new->oo_owner.so_ops =3D &openowner_ops;
> +	new->oo_owner.so_is_open_owner =3D 1;
> +	new->oo_owner.so_seqid =3D open->op_seqid;
> +	new->oo_flags =3D 0;
> +	if (nfsd4_has_session(cstate))
> +		new->oo_flags |=3D NFS4_OO_CONFIRMED;
> +	new->oo_time =3D 0;
> +	new->oo_last_closed_stid =3D NULL;
> +	INIT_LIST_HEAD(&new->oo_close_lru);
> +	goto retry;
>  }
> =20
>  static struct nfs4_ol_stateid *
> @@ -5331,27 +5331,14 @@ nfsd4_process_open1(struct nfsd4_compound_state *=
cstate,
>  	clp =3D cstate->clp;
> =20
>  	strhashval =3D ownerstr_hashval(&open->op_owner);
> -	oo =3D find_openstateowner_str(strhashval, open, clp);
> +	oo =3D find_or_alloc_open_stateowner(strhashval, open, cstate);
>  	open->op_openowner =3D oo;
> -	if (!oo) {
> -		goto new_owner;
> -	}
> -	if (!(oo->oo_flags & NFS4_OO_CONFIRMED)) {
> -		/* Replace unconfirmed owners without checking for replay. */
> -		release_openowner(oo);
> -		open->op_openowner =3D NULL;
> -		goto new_owner;
> -	}
> +	if (!oo)
> +		return nfserr_jukebox;
>  	status =3D nfsd4_check_seqid(cstate, &oo->oo_owner, open->op_seqid);
>  	if (status)
>  		return status;
> -	goto alloc_stateid;
> -new_owner:
> -	oo =3D alloc_init_open_stateowner(strhashval, open, cstate);
> -	if (oo =3D=3D NULL)
> -		return nfserr_jukebox;
> -	open->op_openowner =3D oo;
> -alloc_stateid:
> +
>  	open->op_stp =3D nfs4_alloc_open_stateid(clp);
>  	if (!open->op_stp)
>  		return nfserr_jukebox;

Bonus: this makes the spinlocking in nfsd4_process_open1 simpler too.

Reviewed-by: Jeff Layton <jlayton@kernel.org>