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From:   Chuck Lever III <chuck.lever@oracle.com>
To:     Neil Brown <neilb@suse.de>
CC:     Al Viro <viro@zeniv.linux.org.uk>, Daire Byrne <daire@dneg.com>,
        Trond Myklebust <trond.myklebust@hammerspace.com>,
        Linux NFS Mailing List <linux-nfs@vger.kernel.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 11/12] nfsd: use (un)lock_inode instead of fh_(un)lock
Thread-Topic: [PATCH 11/12] nfsd: use (un)lock_inode instead of fh_(un)lock
Thread-Index: AQHYf3xf15U4Wz2DJE6TlDfjf90TK61espYA
Date:   Fri, 24 Jun 2022 14:43:34 +0000
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> On Jun 13, 2022, at 7:18 PM, NeilBrown <neilb@suse.de> wrote:
>=20
> Except for the xattr changes, these callers don't need to save pre/post
> attrs, so use a simple lock/unlock.
>=20
> For the xattr changes, make the saving of pre/post explicit rather than
> requiring a comment.
>=20
> Also many fh_unlock() are not needed.

This patch does three different (though related) things. I prefer to
instead see three patches:

- One that changes the xattr code, as described
- One that cleans up unneeded fh_unlock calls, with an explanation of
  why that is safe to do
- One that replaces fh_lock() with inode_lock (or inode_lock_nested,
  see below).


> Signed-off-by: NeilBrown <neilb@suse.de>
> ---
> fs/nfsd/nfs2acl.c   |    6 +++---
> fs/nfsd/nfs3acl.c   |    4 ++--
> fs/nfsd/nfs3proc.c  |    4 ----
> fs/nfsd/nfs4acl.c   |    7 +++----
> fs/nfsd/nfs4proc.c  |    2 --
> fs/nfsd/nfs4state.c |    8 ++++----
> fs/nfsd/nfsfh.c     |    1 -
> fs/nfsd/nfsfh.h     |    8 --------
> fs/nfsd/vfs.c       |   26 ++++++++++++--------------
> 9 files changed, 24 insertions(+), 42 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);

fh_lock() uses inode_lock_nested(). If the above hunk is the
correct substitution, the patch description should explain why
that is correct. Otherwise, shall we use inode_lock_nested()
here too?

Likewise throughout.


> 	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/nfs3proc.c b/fs/nfsd/nfs3proc.c
> index d85b110d58dd..7bb07c7e6ee8 100644
> --- a/fs/nfsd/nfs3proc.c
> +++ b/fs/nfsd/nfs3proc.c
> @@ -374,7 +374,6 @@ nfsd3_proc_mkdir(struct svc_rqst *rqstp)
> 	fh_init(&resp->fh, NFS3_FHSIZE);
> 	resp->status =3D nfsd_create(rqstp, &resp->dirfh, argp->name, argp->len,
> 				   &argp->attrs, S_IFDIR, 0, &resp->fh);
> -	fh_unlock(&resp->dirfh);
> 	return rpc_success;
> }
>=20
> @@ -449,7 +448,6 @@ nfsd3_proc_mknod(struct svc_rqst *rqstp)
> 	type =3D nfs3_ftypes[argp->ftype];
> 	resp->status =3D nfsd_create(rqstp, &resp->dirfh, argp->name, argp->len,
> 				   &argp->attrs, type, rdev, &resp->fh);
> -	fh_unlock(&resp->dirfh);
> out:
> 	return rpc_success;
> }
> @@ -472,7 +470,6 @@ nfsd3_proc_remove(struct svc_rqst *rqstp)
> 	fh_copy(&resp->fh, &argp->fh);
> 	resp->status =3D nfsd_unlink(rqstp, &resp->fh, -S_IFDIR,
> 				   argp->name, argp->len);
> -	fh_unlock(&resp->fh);
> 	return rpc_success;
> }
>=20
> @@ -493,7 +490,6 @@ nfsd3_proc_rmdir(struct svc_rqst *rqstp)
> 	fh_copy(&resp->fh, &argp->fh);
> 	resp->status =3D nfsd_unlink(rqstp, &resp->fh, S_IFDIR,
> 				   argp->name, argp->len);
> -	fh_unlock(&resp->fh);
> 	return rpc_success;
> }
>=20
> diff --git a/fs/nfsd/nfs4acl.c b/fs/nfsd/nfs4acl.c
> index eaa3a0cf38f1..7bcc6dc0f762 100644
> --- a/fs/nfsd/nfs4acl.c
> +++ b/fs/nfsd/nfs4acl.c
> @@ -779,19 +779,18 @@ 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/nfs4proc.c b/fs/nfsd/nfs4proc.c
> index 79434e29b63f..d6defaf5a77a 100644
> --- a/fs/nfsd/nfs4proc.c
> +++ b/fs/nfsd/nfs4proc.c
> @@ -860,7 +860,6 @@ nfsd4_create(struct svc_rqst *rqstp, struct nfsd4_com=
pound_state *cstate,
> 		do_set_nfs4_acl(rqstp, &resfh, create->cr_acl,
> 				create->cr_bmval);
>=20
> -	fh_unlock(&cstate->current_fh);
> 	set_change_info(&create->cr_cinfo, &cstate->current_fh);
> 	fh_dup2(&cstate->current_fh, &resfh);
> out:
> @@ -1040,7 +1039,6 @@ nfsd4_remove(struct svc_rqst *rqstp, struct nfsd4_c=
ompound_state *cstate,
> 	status =3D nfsd_unlink(rqstp, &cstate->current_fh, 0,
> 			     remove->rm_name, remove->rm_namelen);
> 	if (!status) {
> -		fh_unlock(&cstate->current_fh);
> 		set_change_info(&remove->rm_cinfo, &cstate->current_fh);
> 	}
> 	return status;
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index 9409a0dc1b76..cb664c61b546 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -7321,21 +7321,21 @@ 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;
> 	__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/nfsfh.c b/fs/nfsd/nfsfh.c
> index a50db688c60d..ae270e4f921f 100644
> --- a/fs/nfsd/nfsfh.c
> +++ b/fs/nfsd/nfsfh.c
> @@ -685,7 +685,6 @@ fh_put(struct svc_fh *fhp)
> 	struct dentry * dentry =3D fhp->fh_dentry;
> 	struct svc_export * exp =3D fhp->fh_export;
> 	if (dentry) {
> -		fh_unlock(fhp);
> 		fhp->fh_dentry =3D NULL;
> 		dput(dentry);
> 		fh_clear_pre_post_attrs(fhp);
> diff --git a/fs/nfsd/nfsfh.h b/fs/nfsd/nfsfh.h
> index ecc57fd3fd67..c5061cdb1016 100644
> --- a/fs/nfsd/nfsfh.h
> +++ b/fs/nfsd/nfsfh.h
> @@ -323,14 +323,6 @@ static inline u64 nfsd4_change_attribute(struct ksta=
t *stat,
> extern void fh_fill_pre_attrs(struct svc_fh *fhp, bool atomic);
> extern void fh_fill_post_attrs(struct svc_fh *fhp);
>=20
> -
> -/*
> - * Lock a file handle/inode
> - * NOTE: both fh_lock and fh_unlock are done "by hand" in
> - * vfs.c:nfsd_rename as it needs to grab 2 i_mutex's at once
> - * so, any changes here should be reflected there.
> - */
> -
> static inline void
> fh_lock_nested(struct svc_fh *fhp, unsigned int subclass)
> {
> diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
> index 4c2e431100ba..f2f4868618bb 100644
> --- a/fs/nfsd/vfs.c
> +++ b/fs/nfsd/vfs.c
> @@ -253,7 +253,6 @@ nfsd_lookup_dentry(struct svc_rqst *rqstp, struct svc=
_fh *fhp,
>  * returned. Otherwise the covered directory is returned.
>  * NOTE: this mountpoint crossing is not supported properly by all
>  *   clients and is explicitly disallowed for NFSv3
> - *      NeilBrown <neilb@cse.unsw.edu.au>
>  */
> __be32
> nfsd_lookup(struct svc_rqst *rqstp, struct svc_fh *fhp, const char *name,
> @@ -434,7 +433,7 @@ 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:
> @@ -470,7 +469,7 @@ 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:
> @@ -2123,12 +2122,8 @@ 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)
> @@ -2144,12 +2139,14 @@ 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, true);
>=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);
> @@ -2169,12 +2166,13 @@ 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, true);
>=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