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From:   Chuck Lever III <chuck.lever@oracle.com>
To:     Neil Brown <neilb@suse.de>
CC:     Jeff Layton <jlayton@kernel.org>,
        Linux NFS Mailing List <linux-nfs@vger.kernel.org>
Subject: Re: [PATCH 7/8] NFSD: use (un)lock_inode instead of fh_(un)lock for
 file operations
Thread-Topic: [PATCH 7/8] NFSD: use (un)lock_inode instead of fh_(un)lock for
 file operations
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Date:   Wed, 6 Jul 2022 16:30:12 +0000
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> On Jul 6, 2022, at 12:18 AM, NeilBrown <neilb@suse.de> wrote:
>=20
> When locking a file to access ACLs and xattrs etc, use explicit locking
> with inode_lock() instead of fh_lock().  This means that the calls to
> fh_fill_pre/post_attr() are also explicit which improves readability and
> allows us to place them only where they are needed.  Only the xattr
> calls need pre/post information.
>=20
> When locking a file we don't need I_MUTEX_PARENT as the file is not a
> parent of anything, so we can use inode_lock() directly rather than the
> inode_lock_nested() call that fh_lock() uses.
>=20
> Signed-off-by: NeilBrown <neilb@suse.de>
> ---
> fs/nfsd/nfs2acl.c   |    6 +++---
> fs/nfsd/nfs3acl.c   |    4 ++--
> fs/nfsd/nfs4acl.c   |    7 +++----
> fs/nfsd/nfs4state.c |    8 ++++----
> fs/nfsd/vfs.c       |   25 ++++++++++++-------------
> 5 files changed, 24 insertions(+), 26 deletions(-)
>=20
> diff --git a/fs/nfsd/nfs2acl.c b/fs/nfsd/nfs2acl.c
> index b5760801d377..9edd3c1a30fb 100644
> --- a/fs/nfsd/nfs2acl.c
> +++ b/fs/nfsd/nfs2acl.c
> @@ -111,7 +111,7 @@ static __be32 nfsacld_proc_setacl(struct svc_rqst *rq=
stp)
> 	if (error)
> 		goto out_errno;
>=20
> -	fh_lock(fh);
> +	inode_lock(inode);
>=20
> 	error =3D set_posix_acl(&init_user_ns, inode, ACL_TYPE_ACCESS,
> 			      argp->acl_access);
> @@ -122,7 +122,7 @@ static __be32 nfsacld_proc_setacl(struct svc_rqst *rq=
stp)
> 	if (error)
> 		goto out_drop_lock;
>=20
> -	fh_unlock(fh);
> +	inode_unlock(inode);
>=20
> 	fh_drop_write(fh);
>=20
> @@ -136,7 +136,7 @@ static __be32 nfsacld_proc_setacl(struct svc_rqst *rq=
stp)
> 	return rpc_success;
>=20
> out_drop_lock:
> -	fh_unlock(fh);
> +	inode_unlock(inode);
> 	fh_drop_write(fh);
> out_errno:
> 	resp->status =3D nfserrno(error);
> diff --git a/fs/nfsd/nfs3acl.c b/fs/nfsd/nfs3acl.c
> index 35b2ebda14da..9446c6743664 100644
> --- a/fs/nfsd/nfs3acl.c
> +++ b/fs/nfsd/nfs3acl.c
> @@ -101,7 +101,7 @@ static __be32 nfsd3_proc_setacl(struct svc_rqst *rqst=
p)
> 	if (error)
> 		goto out_errno;
>=20
> -	fh_lock(fh);
> +	inode_lock(inode);
>=20
> 	error =3D set_posix_acl(&init_user_ns, inode, ACL_TYPE_ACCESS,
> 			      argp->acl_access);
> @@ -111,7 +111,7 @@ static __be32 nfsd3_proc_setacl(struct svc_rqst *rqst=
p)
> 			      argp->acl_default);
>=20
> out_drop_lock:
> -	fh_unlock(fh);
> +	inode_unlock(inode);
> 	fh_drop_write(fh);
> out_errno:
> 	resp->status =3D nfserrno(error);
> diff --git a/fs/nfsd/nfs4acl.c b/fs/nfsd/nfs4acl.c
> index 5c9b7e01e8ca..a33cacf62ea0 100644
> --- a/fs/nfsd/nfs4acl.c
> +++ b/fs/nfsd/nfs4acl.c
> @@ -781,19 +781,18 @@ nfsd4_set_nfs4_acl(struct svc_rqst *rqstp, struct s=
vc_fh *fhp,
> 	if (host_error < 0)
> 		goto out_nfserr;
>=20
> -	fh_lock(fhp);
> +	inode_lock(inode);
>=20
> 	host_error =3D set_posix_acl(&init_user_ns, inode, ACL_TYPE_ACCESS, pacl=
);
> 	if (host_error < 0)
> 		goto out_drop_lock;
>=20
> -	if (S_ISDIR(inode->i_mode)) {
> +	if (S_ISDIR(inode->i_mode))
> 		host_error =3D set_posix_acl(&init_user_ns, inode,
> 					   ACL_TYPE_DEFAULT, dpacl);
> -	}
>=20
> out_drop_lock:
> -	fh_unlock(fhp);
> +	inode_unlock(inode);
>=20
> 	posix_acl_release(pacl);
> 	posix_acl_release(dpacl);
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index 9d1a3e131c49..307317ba9aff 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -7322,21 +7322,21 @@ nfsd4_lock(struct svc_rqst *rqstp, struct nfsd4_c=
ompound_state *cstate,
> static __be32 nfsd_test_lock(struct svc_rqst *rqstp, struct svc_fh *fhp, =
struct file_lock *lock)
> {
> 	struct nfsd_file *nf;
> +	struct inode *inode =3D fhp->fh_dentry->d_inode;

I don't think this is correct.

nfsd_file_acquire() calls fh_verify(), which can updated fhp->fh_dentry.
Anyway, is it guaranteed that fh_dentry is not NULL here?

It would be more defensive to set @inode /after/ the call to
nfsd_file_acquire().


> 	__be32 err;
>=20
> 	err =3D nfsd_file_acquire(rqstp, fhp, NFSD_MAY_READ, &nf);
> 	if (err)
> 		return err;
> -	fh_lock(fhp); /* to block new leases till after test_lock: */
> -	err =3D nfserrno(nfsd_open_break_lease(fhp->fh_dentry->d_inode,
> -							NFSD_MAY_READ));
> +	inode_lock(inode); /* to block new leases till after test_lock: */
> +	err =3D nfserrno(nfsd_open_break_lease(inode, NFSD_MAY_READ));
> 	if (err)
> 		goto out;
> 	lock->fl_file =3D nf->nf_file;
> 	err =3D nfserrno(vfs_test_lock(nf->nf_file, lock));
> 	lock->fl_file =3D NULL;
> out:
> -	fh_unlock(fhp);
> +	inode_unlock(inode);
> 	nfsd_file_put(nf);
> 	return err;
> }
> diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
> index 2ca748aa83bb..2526615285ca 100644
> --- a/fs/nfsd/vfs.c
> +++ b/fs/nfsd/vfs.c
> @@ -444,7 +444,7 @@ nfsd_setattr(struct svc_rqst *rqstp, struct svc_fh *f=
hp, struct iattr *iap,
> 			return err;
> 	}
>=20
> -	fh_lock(fhp);
> +	inode_lock(inode);
> 	if (size_change) {
> 		/*
> 		 * RFC5661, Section 18.30.4:
> @@ -480,7 +480,7 @@ nfsd_setattr(struct svc_rqst *rqstp, struct svc_fh *f=
hp, struct iattr *iap,
> 	host_err =3D notify_change(&init_user_ns, dentry, iap, NULL);
>=20
> out_unlock:
> -	fh_unlock(fhp);
> +	inode_unlock(inode);
> 	if (size_change)
> 		put_write_access(inode);
> out:
> @@ -2196,12 +2196,8 @@ nfsd_listxattr(struct svc_rqst *rqstp, struct svc_=
fh *fhp, char **bufp,
> }
>=20
> /*
> - * Removexattr and setxattr need to call fh_lock to both lock the inode
> - * and set the change attribute. Since the top-level vfs_removexattr
> - * and vfs_setxattr calls already do their own inode_lock calls, call
> - * the _locked variant. Pass in a NULL pointer for delegated_inode,
> - * and let the client deal with NFS4ERR_DELAY (same as with e.g.
> - * setattr and remove).
> + * Pass in a NULL pointer for delegated_inode, and let the client deal
> + * with NFS4ERR_DELAY (same as with e.g.  setattr and remove).
>  */
> __be32
> nfsd_removexattr(struct svc_rqst *rqstp, struct svc_fh *fhp, char *name)
> @@ -2217,12 +2213,14 @@ nfsd_removexattr(struct svc_rqst *rqstp, struct s=
vc_fh *fhp, char *name)
> 	if (ret)
> 		return nfserrno(ret);
>=20
> -	fh_lock(fhp);
> +	inode_lock(fhp->fh_dentry->d_inode);
> +	fh_fill_pre_attrs(fhp);
>=20
> 	ret =3D __vfs_removexattr_locked(&init_user_ns, fhp->fh_dentry,
> 				       name, NULL);
>=20
> -	fh_unlock(fhp);
> +	fh_fill_post_attrs(fhp);
> +	inode_unlock(fhp->fh_dentry->d_inode);
> 	fh_drop_write(fhp);
>=20
> 	return nfsd_xattr_errno(ret);
> @@ -2242,12 +2240,13 @@ nfsd_setxattr(struct svc_rqst *rqstp, struct svc_=
fh *fhp, char *name,
> 	ret =3D fh_want_write(fhp);
> 	if (ret)
> 		return nfserrno(ret);
> -	fh_lock(fhp);
> +	inode_lock(fhp->fh_dentry->d_inode);
> +	fh_fill_pre_attrs(fhp);
>=20
> 	ret =3D __vfs_setxattr_locked(&init_user_ns, fhp->fh_dentry, name, buf,
> 				    len, flags, NULL);
> -
> -	fh_unlock(fhp);
> +	fh_fill_post_attrs(fhp);
> +	inode_unlock(fhp->fh_dentry->d_inode);
> 	fh_drop_write(fhp);
>=20
> 	return nfsd_xattr_errno(ret);
>=20
>=20

--
Chuck Lever