[RFC PATCH 05/11] NFSD: add NFS4 reexport support for SETACL nfs4_acl passthru

[Mike Snitzer <snitzer@kernel.org>]

From: Mike Snitzer <snitzer@hammerspace.com>

Allow NFSD's 4.1 reexport of a 4.2 mount to perform SETACL by passing
thru nfs4_acl that was decoded from 4.1 client directly to 4.2
client.

Update nfsd4_decode_acl() to save the ACL's payload off to an xdr_buf
in the nfs4_acl. But only do the work to decode that ACL payload into
pages stored in the nfs4_acl, via nfsd4_decode_nfs4_acl_passthru(), if
the exported filesystem supports nfs4_acl passthru (like NFSv4 client
does).

Signed-off-by: Mike Snitzer <snitzer@hammerspace.com>
---
 fs/nfsd/nfs4proc.c | 27 +++++++++++++++++++++------
 fs/nfsd/nfs4xdr.c  | 43 ++++++++++++++++++++++++++++++++++++++++++-
 fs/nfsd/xdr4.h     |  2 ++
 3 files changed, 65 insertions(+), 7 deletions(-)

diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index 9a21e94a4215..796954a24cde 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -1219,6 +1219,7 @@ nfsd4_setattr(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 	};
 	bool save_no_wcc, deleg_attrs;
 	struct nfs4_stid *st = NULL;
+	struct dentry *dentry;
 	struct inode *inode;
 	__be32 status = nfs_ok;
 	int err;
@@ -1276,12 +1277,14 @@ nfsd4_setattr(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 		goto out;
 	}
 
-	inode = cstate->current_fh.fh_dentry->d_inode;
-	status = nfsd4_acl_to_attr(S_ISDIR(inode->i_mode) ? NF4DIR : NF4REG,
-				   setattr->sa_acl, &attrs);
-
-	if (status)
-		goto out;
+	dentry = cstate->current_fh.fh_dentry;
+	inode = dentry->d_inode;
+	if (IS_POSIXACL(inode)) {
+		status = nfsd4_acl_to_attr(S_ISDIR(inode->i_mode) ? NF4DIR : NF4REG,
+					   setattr->sa_acl, &attrs);
+		if (status)
+			goto out;
+	}
 	save_no_wcc = cstate->current_fh.fh_no_wcc;
 	cstate->current_fh.fh_no_wcc = true;
 	status = nfsd_setattr(rqstp, &cstate->current_fh, &attrs, NULL);
@@ -1292,6 +1295,18 @@ nfsd4_setattr(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 		status = nfserrno(attrs.na_dpaclerr);
 	if (!status)
 		status = nfserrno(attrs.na_paclerr);
+	if (!status && !IS_POSIXACL(inode) && setattr->sa_acl &&
+	    exportfs_may_passthru_nfs4acl(dentry->d_sb->s_export_op)) {
+		const struct export_operations *ops = dentry->d_sb->s_export_op;
+		if (likely(ops->setacl)) {
+			status = nfsd4_decode_nfs4_acl_passthru(rqstp->rq_argp,
+					setattr->sa_bmval, &setattr->sa_acl);
+			if (status)
+				goto out;
+			status = nfserrno(ops->setacl(inode, setattr->sa_acl));
+		} else
+			status = nfserr_attrnotsupp;
+	}
 out:
 	fh_drop_write(&cstate->current_fh);
 out_err:
diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index cacdd6285e90..f14c2fb45142 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -287,6 +287,45 @@ nfsd4_decode_bitmap4(struct nfsd4_compoundargs *argp, u32 *bmval, u32 bmlen)
 	return status == -EBADMSG ? nfserr_bad_xdr : nfs_ok;
 }
 
+__be32 nfsd4_decode_nfs4_acl_passthru(struct nfsd4_compoundargs *argp,
+				      u32 *bmval, struct nfs4_acl **acl)
+{
+	u32 acl_len = (*acl)->payload.len;
+	unsigned int pgbase, num_pages;
+	struct xdr_stream xdr;
+	__be32 status = nfs_ok;
+	void *p;
+
+	xdr_init_decode(&xdr, &(*acl)->payload,
+			(*acl)->payload.head[0].iov_base, NULL);
+
+	p = xdr_inline_decode(&xdr, acl_len);
+	if (p == NULL) {
+		status = nfserr_bad_xdr;
+		goto out;
+	}
+
+	pgbase = (unsigned long)p & ~PAGE_MASK;
+	num_pages = DIV_ROUND_UP(pgbase + acl_len, PAGE_SIZE);
+
+	*acl = svcxdr_tmpalloc(argp, (sizeof(struct nfs4_acl) +
+				      num_pages * sizeof(struct page *)));
+	if (*acl == NULL) {
+		status = nfserr_jukebox;
+		goto out;
+	}
+
+	(*acl)->type = NFS4ACL_ACL;
+	(*acl)->len = acl_len;
+	(*acl)->pgbase = pgbase;
+
+	for (int i = 0; i < num_pages; i++)
+		(*acl)->pages[i] = virt_to_page(p + (i << PAGE_SHIFT));
+out:
+	xdr_finish_decode(&xdr);
+	return status;
+}
+
 static __be32
 nfsd4_decode_nfsace4(struct xdr_stream *xdr, struct svc_rqst *rqstp,
 		     struct nfs4_ace *ace)
@@ -325,7 +364,7 @@ nfsd4_decode_acl(struct nfsd4_compoundargs *argp, struct nfs4_acl **acl,
 		 u32 acl_len)
 {
 
-	struct xdr_buf payload;
+	struct xdr_buf payload, saved_payload;
 	struct xdr_stream xdr;
 	struct nfs4_ace *ace;
 	__be32 status = nfs_ok;
@@ -333,6 +372,7 @@ nfsd4_decode_acl(struct nfsd4_compoundargs *argp, struct nfs4_acl **acl,
 
 	if (!xdr_stream_subsegment(argp->xdr, &payload, acl_len))
 		return nfserr_bad_xdr;
+	memcpy(&saved_payload, &payload, sizeof(struct xdr_buf));
 
 	xdr_init_decode(&xdr, &payload, payload.head[0].iov_base, NULL);
 
@@ -356,6 +396,7 @@ nfsd4_decode_acl(struct nfsd4_compoundargs *argp, struct nfs4_acl **acl,
 		status = nfserr_jukebox;
 		goto out;
 	}
+	memcpy(&(*acl)->payload, &saved_payload, sizeof(struct xdr_buf));
 
 	(*acl)->naces = count;
 	for (ace = (*acl)->aces; ace < (*acl)->aces + count; ace++) {
diff --git a/fs/nfsd/xdr4.h b/fs/nfsd/xdr4.h
index 417e9ad9fbb3..d3561ce76a12 100644
--- a/fs/nfsd/xdr4.h
+++ b/fs/nfsd/xdr4.h
@@ -1011,6 +1011,8 @@ extern __be32 nfsd4_test_stateid(struct svc_rqst *rqstp,
 extern __be32 nfsd4_free_stateid(struct svc_rqst *rqstp,
 		struct nfsd4_compound_state *, union nfsd4_op_u *);
 extern void nfsd4_bump_seqid(struct nfsd4_compound_state *, __be32 nfserr);
+__be32 nfsd4_decode_nfs4_acl_passthru(struct nfsd4_compoundargs *,
+		u32 *bmval, struct nfs4_acl **acl);
 
 enum nfsd4_op_flags {
 	ALLOWED_WITHOUT_FH = 1 << 0,    /* No current filehandle required */
-- 
2.44.0