nfsd4: teach encoders to handle reserve_space failures

We've tried to prevent running out of space with COMPOUND_SLACK_SPACE
and special checking in those operations (getattr) whose result can vary
enormously.

However:
	- COMPOUND_SLACK_SPACE may be difficult to maintain as we add
	  more protocol.
	- BUG_ON or page faulting on failure seems overly fragile.
	- Especially in the 4.1 case, we prefer not to fail compounds
	  just because the returned result came *close* to session
	  limits.  (Though perfect enforcement here may be difficult.)
	- I'd prefer encoding to be uniform for all encoders instead of
	  having special exceptions for encoders containing, for
	  example, attributes.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>

3 files changed, 185 insertions, 66 deletions

diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index ef3952ac65b9..6a5b701961a4 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -1400,7 +1400,7 @@ encode_op:
                 }
                 if (op->status == nfserr_replay_me) {
                         op->replay = &cstate->replay_owner->so_replay;
-                        nfsd4_encode_replay(resp, op);
+                        nfsd4_encode_replay(&resp->xdr, op);
                         status = op->status = op->replay->rp_status;
                 } else {
                         nfsd4_encode_operation(resp, op);
diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 37a73c8cda61..799a90479487 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -1746,11 +1746,6 @@ static void write_cinfo(__be32 **p, struct nfsd4_change_info *c)
         }
 }
 
-#define RESERVE_SPACE(nbytes)   do {                            \
-        p = xdr_reserve_space(&resp->xdr, nbytes);              \
-        BUG_ON(!p);                                             \
-} while (0)
-
 /* Encode as an array of strings the string given with components
  * separated @sep, escaped with esc_enter and esc_exit.
  */
@@ -2737,23 +2732,29 @@ fail:
         return -EINVAL;
 }
 
-static void
-nfsd4_encode_stateid(struct nfsd4_compoundres *resp, stateid_t *sid)
+static __be32
+nfsd4_encode_stateid(struct xdr_stream *xdr, stateid_t *sid)
 {
         __be32 *p;
 
-        RESERVE_SPACE(sizeof(stateid_t));
+        p = xdr_reserve_space(xdr, sizeof(stateid_t));
+        if (!p)
+                return nfserr_resource;
         WRITE32(sid->si_generation);
         WRITEMEM(&sid->si_opaque, sizeof(stateid_opaque_t));
+        return 0;
 }
 
 static __be32
 nfsd4_encode_access(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_access *access)
 {
+        struct xdr_stream *xdr = &resp->xdr;
         __be32 *p;
 
         if (!nfserr) {
-                RESERVE_SPACE(8);
+                p = xdr_reserve_space(xdr, 8);
+                if (!p)
+                        return nfserr_resource;
                 WRITE32(access->ac_supported);
                 WRITE32(access->ac_resp_access);
         }
@@ -2762,10 +2763,13 @@ nfsd4_encode_access(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_
 
 static __be32 nfsd4_encode_bind_conn_to_session(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_bind_conn_to_session *bcts)
 {
+        struct xdr_stream *xdr = &resp->xdr;
         __be32 *p;
 
         if (!nfserr) {
-                RESERVE_SPACE(NFS4_MAX_SESSIONID_LEN + 8);
+                p = xdr_reserve_space(xdr, NFS4_MAX_SESSIONID_LEN + 8);
+                if (!p)
+                        return nfserr_resource;
                 WRITEMEM(bcts->sessionid.data, NFS4_MAX_SESSIONID_LEN);
                 WRITE32(bcts->dir);
                 /* Sorry, we do not yet support RDMA over 4.1: */
@@ -2777,8 +2781,10 @@ static __be32 nfsd4_encode_bind_conn_to_session(struct nfsd4_compoundres *resp,
 static __be32
 nfsd4_encode_close(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_close *close)
 {
+        struct xdr_stream *xdr = &resp->xdr;
+
         if (!nfserr)
-                nfsd4_encode_stateid(resp, &close->cl_stateid);
+                nfserr = nfsd4_encode_stateid(xdr, &close->cl_stateid);
 
         return nfserr;
 }
@@ -2787,10 +2793,13 @@ nfsd4_encode_close(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_c
 static __be32
 nfsd4_encode_commit(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_commit *commit)
 {
+        struct xdr_stream *xdr = &resp->xdr;
         __be32 *p;
 
         if (!nfserr) {
-                RESERVE_SPACE(NFS4_VERIFIER_SIZE);
+                p = xdr_reserve_space(xdr, NFS4_VERIFIER_SIZE);
+                if (!p)
+                        return nfserr_resource;
                 WRITEMEM(commit->co_verf.data, NFS4_VERIFIER_SIZE);
         }
         return nfserr;
@@ -2799,10 +2808,13 @@ nfsd4_encode_commit(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_
 static __be32
 nfsd4_encode_create(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_create *create)
 {
+        struct xdr_stream *xdr = &resp->xdr;
         __be32 *p;
 
         if (!nfserr) {
-                RESERVE_SPACE(32);
+                p = xdr_reserve_space(xdr, 32);
+                if (!p)
+                        return nfserr_resource;
                 write_cinfo(&p, &create->cr_cinfo);
                 WRITE32(2);
                 WRITE32(create->cr_bmval[0]);
@@ -2829,13 +2841,16 @@ nfsd4_encode_getattr(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4
 static __be32
 nfsd4_encode_getfh(struct nfsd4_compoundres *resp, __be32 nfserr, struct svc_fh **fhpp)
 {
+        struct xdr_stream *xdr = &resp->xdr;
         struct svc_fh *fhp = *fhpp;
         unsigned int len;
         __be32 *p;
 
         if (!nfserr) {
                 len = fhp->fh_handle.fh_size;
-                RESERVE_SPACE(len + 4);
+                p = xdr_reserve_space(xdr, len + 4);
+                if (!p)
+                        return nfserr_resource;
                 WRITE32(len);
                 WRITEMEM(&fhp->fh_handle.fh_base, len);
         }
@@ -2846,13 +2861,15 @@ nfsd4_encode_getfh(struct nfsd4_compoundres *resp, __be32 nfserr, struct svc_fh
 * Including all fields other than the name, a LOCK4denied structure requires
 *   8(clientid) + 4(namelen) + 8(offset) + 8(length) + 4(type) = 32 bytes.
 */
-static void
-nfsd4_encode_lock_denied(struct nfsd4_compoundres *resp, struct nfsd4_lock_denied *ld)
+static __be32
+nfsd4_encode_lock_denied(struct xdr_stream *xdr, struct nfsd4_lock_denied *ld)
 {
         struct xdr_netobj *conf = &ld->ld_owner;
         __be32 *p;
 
-        RESERVE_SPACE(32 + XDR_LEN(conf->len));
+        p = xdr_reserve_space(xdr, 32 + XDR_LEN(conf->len));
+        if (!p)
+                return nfserr_resource;
         WRITE64(ld->ld_start);
         WRITE64(ld->ld_length);
         WRITE32(ld->ld_type);
@@ -2865,15 +2882,18 @@ nfsd4_encode_lock_denied(struct nfsd4_compoundres *resp, struct nfsd4_lock_denie
                 WRITE64((u64)0); /* clientid */
                 WRITE32(0); /* length of owner name */
         }
+        return nfserr_denied;
 }
 
 static __be32
 nfsd4_encode_lock(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_lock *lock)
 {
+        struct xdr_stream *xdr = &resp->xdr;
+
         if (!nfserr)
-                nfsd4_encode_stateid(resp, &lock->lk_resp_stateid);
+                nfserr = nfsd4_encode_stateid(xdr, &lock->lk_resp_stateid);
         else if (nfserr == nfserr_denied)
-                nfsd4_encode_lock_denied(resp, &lock->lk_denied);
+                nfserr = nfsd4_encode_lock_denied(xdr, &lock->lk_denied);
 
         return nfserr;
 }
@@ -2881,16 +2901,20 @@ nfsd4_encode_lock(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_lo
 static __be32
 nfsd4_encode_lockt(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_lockt *lockt)
 {
+        struct xdr_stream *xdr = &resp->xdr;
+
         if (nfserr == nfserr_denied)
-                nfsd4_encode_lock_denied(resp, &lockt->lt_denied);
+                nfsd4_encode_lock_denied(xdr, &lockt->lt_denied);
         return nfserr;
 }
 
 static __be32
 nfsd4_encode_locku(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_locku *locku)
 {
+        struct xdr_stream *xdr = &resp->xdr;
+
         if (!nfserr)
-                nfsd4_encode_stateid(resp, &locku->lu_stateid);
+                nfserr = nfsd4_encode_stateid(xdr, &locku->lu_stateid);
 
         return nfserr;
 }
@@ -2899,10 +2923,13 @@ nfsd4_encode_locku(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_l
 static __be32
 nfsd4_encode_link(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_link *link)
 {
+        struct xdr_stream *xdr = &resp->xdr;
         __be32 *p;
 
         if (!nfserr) {
-                RESERVE_SPACE(20);
+                p = xdr_reserve_space(xdr, 20);
+                if (!p)
+                        return nfserr_resource;
                 write_cinfo(&p, &link->li_cinfo);
         }
         return nfserr;
@@ -2912,13 +2939,18 @@ nfsd4_encode_link(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_li
 static __be32
 nfsd4_encode_open(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_open *open)
 {
+        struct xdr_stream *xdr = &resp->xdr;
         __be32 *p;
 
         if (nfserr)
                 goto out;
 
-        nfsd4_encode_stateid(resp, &open->op_stateid);
-        RESERVE_SPACE(40);
+        nfserr = nfsd4_encode_stateid(xdr, &open->op_stateid);
+        if (nfserr)
+                goto out;
+        p = xdr_reserve_space(xdr, 40);
+        if (!p)
+                return nfserr_resource;
         write_cinfo(&p, &open->op_cinfo);
         WRITE32(open->op_rflags);
         WRITE32(2);
@@ -2930,8 +2962,12 @@ nfsd4_encode_open(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_op
         case NFS4_OPEN_DELEGATE_NONE:
                 break;
         case NFS4_OPEN_DELEGATE_READ:
-                nfsd4_encode_stateid(resp, &open->op_delegate_stateid);
-                RESERVE_SPACE(20);
+                nfserr = nfsd4_encode_stateid(xdr, &open->op_delegate_stateid);
+                if (nfserr)
+                        return nfserr;
+                p = xdr_reserve_space(xdr, 20);
+                if (!p)
+                        return nfserr_resource;
                 WRITE32(open->op_recall);
 
                 /*
@@ -2943,8 +2979,12 @@ nfsd4_encode_open(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_op
                 WRITE32(0);   /* XXX: is NULL principal ok? */
                 break;
         case NFS4_OPEN_DELEGATE_WRITE:
-                nfsd4_encode_stateid(resp, &open->op_delegate_stateid);
-                RESERVE_SPACE(32);
+                nfserr = nfsd4_encode_stateid(xdr, &open->op_delegate_stateid);
+                if (nfserr)
+                        return nfserr;
+                p = xdr_reserve_space(xdr, 32);
+                if (!p)
+                        return nfserr_resource;
                 WRITE32(0);
 
                 /*
@@ -2966,12 +3006,16 @@ nfsd4_encode_open(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_op
                 switch (open->op_why_no_deleg) {
                 case WND4_CONTENTION:
                 case WND4_RESOURCE:
-                        RESERVE_SPACE(8);
+                        p = xdr_reserve_space(xdr, 8);
+                        if (!p)
+                                return nfserr_resource;
                         WRITE32(open->op_why_no_deleg);
                         WRITE32(0);     /* deleg signaling not supported yet */
                         break;
                 default:
-                        RESERVE_SPACE(4);
+                        p = xdr_reserve_space(xdr, 4);
+                        if (!p)
+                                return nfserr_resource;
                         WRITE32(open->op_why_no_deleg);
                 }
                 break;
@@ -2986,8 +3030,10 @@ out:
 static __be32
 nfsd4_encode_open_confirm(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_open_confirm *oc)
 {
+        struct xdr_stream *xdr = &resp->xdr;
+
         if (!nfserr)
-                nfsd4_encode_stateid(resp, &oc->oc_resp_stateid);
+                nfserr = nfsd4_encode_stateid(xdr, &oc->oc_resp_stateid);
 
         return nfserr;
 }
@@ -2995,8 +3041,10 @@ nfsd4_encode_open_confirm(struct nfsd4_compoundres *resp, __be32 nfserr, struct
 static __be32
 nfsd4_encode_open_downgrade(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_open_downgrade *od)
 {
+        struct xdr_stream *xdr = &resp->xdr;
+
         if (!nfserr)
-                nfsd4_encode_stateid(resp, &od->od_stateid);
+                nfserr = nfsd4_encode_stateid(xdr, &od->od_stateid);
 
         return nfserr;
 }
@@ -3019,7 +3067,9 @@ nfsd4_encode_read(struct nfsd4_compoundres *resp, __be32 nfserr,
         if (resp->xdr.buf->page_len)
                 return nfserr_resource;
 
-        RESERVE_SPACE(8); /* eof flag and byte count */
+        p = xdr_reserve_space(xdr, 8); /* eof flag and byte count */
+        if (!p)
+                return nfserr_resource;
 
         maxcount = svc_max_payload(resp->rqstp);
         if (maxcount > read->rd_length)
@@ -3071,7 +3121,9 @@ nfsd4_encode_read(struct nfsd4_compoundres *resp, __be32 nfserr,
         resp->xdr.buf->tail[0].iov_base = p;
         resp->xdr.buf->tail[0].iov_len = 0;
         if (maxcount&3) {
-                RESERVE_SPACE(4);
+                p = xdr_reserve_space(xdr, 4);
+                if (!p)
+                        return nfserr_resource;
                 WRITE32(0);
                 resp->xdr.buf->tail[0].iov_base += maxcount&3;
                 resp->xdr.buf->tail[0].iov_len = 4 - (maxcount&3);
@@ -3099,7 +3151,10 @@ nfsd4_encode_readlink(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd
         page = page_address(*(resp->rqstp->rq_next_page++));
 
         maxcount = PAGE_SIZE;
-        RESERVE_SPACE(4);
+
+        p = xdr_reserve_space(xdr, 4);
+        if (!p)
+                return nfserr_resource;
 
         /*
          * XXX: By default, the ->readlink() VFS op will truncate symlinks
@@ -3126,7 +3181,9 @@ nfsd4_encode_readlink(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd
         resp->xdr.buf->tail[0].iov_base = p;
         resp->xdr.buf->tail[0].iov_len = 0;
         if (maxcount&3) {
-                RESERVE_SPACE(4);
+                p = xdr_reserve_space(xdr, 4);
+                if  (!p)
+                        return nfserr_resource;
                 WRITE32(0);
                 resp->xdr.buf->tail[0].iov_base += maxcount&3;
                 resp->xdr.buf->tail[0].iov_len = 4 - (maxcount&3);
@@ -3151,7 +3208,9 @@ nfsd4_encode_readdir(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4
         if (!*resp->rqstp->rq_next_page)
                 return nfserr_resource;
 
-        RESERVE_SPACE(NFS4_VERIFIER_SIZE);
+        p = xdr_reserve_space(xdr, NFS4_VERIFIER_SIZE);
+        if (!p)
+                return nfserr_resource;
 
         /* XXX: Following NFSv3, we ignore the READDIR verifier for now. */
         WRITE32(0);
@@ -3220,10 +3279,13 @@ err_no_verf:
 static __be32
 nfsd4_encode_remove(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_remove *remove)
 {
+        struct xdr_stream *xdr = &resp->xdr;
         __be32 *p;
 
         if (!nfserr) {
-                RESERVE_SPACE(20);
+                p = xdr_reserve_space(xdr, 20);
+                if (!p)
+                        return nfserr_resource;
                 write_cinfo(&p, &remove->rm_cinfo);
         }
         return nfserr;
@@ -3232,10 +3294,13 @@ nfsd4_encode_remove(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_
 static __be32
 nfsd4_encode_rename(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_rename *rename)
 {
+        struct xdr_stream *xdr = &resp->xdr;
         __be32 *p;
 
         if (!nfserr) {
-                RESERVE_SPACE(40);
+                p = xdr_reserve_space(xdr, 40);
+                if (!p)
+                        return nfserr_resource;
                 write_cinfo(&p, &rename->rn_sinfo);
                 write_cinfo(&p, &rename->rn_tinfo);
         }
@@ -3243,7 +3308,7 @@ nfsd4_encode_rename(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_
 }
 
 static __be32
-nfsd4_do_encode_secinfo(struct nfsd4_compoundres *resp,
+nfsd4_do_encode_secinfo(struct xdr_stream *xdr,
                          __be32 nfserr, struct svc_export *exp)
 {
         u32 i, nflavs, supported;
@@ -3254,6 +3319,7 @@ nfsd4_do_encode_secinfo(struct nfsd4_compoundres *resp,
 
         if (nfserr)
                 goto out;
+        nfserr = nfserr_resource;
         if (exp->ex_nflavors) {
                 flavs = exp->ex_flavors;
                 nflavs = exp->ex_nflavors;
@@ -3275,7 +3341,9 @@ nfsd4_do_encode_secinfo(struct nfsd4_compoundres *resp,
         }
 
         supported = 0;
-        RESERVE_SPACE(4);
+        p = xdr_reserve_space(xdr, 4);
+        if (!p)
+                goto out;
         flavorsp = p++;         /* to be backfilled later */
 
         for (i = 0; i < nflavs; i++) {
@@ -3284,7 +3352,10 @@ nfsd4_do_encode_secinfo(struct nfsd4_compoundres *resp,
 
                 if (rpcauth_get_gssinfo(pf, &info) == 0) {
                         supported++;
-                        RESERVE_SPACE(4 + 4 + XDR_LEN(info.oid.len) + 4 + 4);
+                        p = xdr_reserve_space(xdr, 4 + 4 +
+                                              XDR_LEN(info.oid.len) + 4 + 4);
+                        if (!p)
+                                goto out;
                         WRITE32(RPC_AUTH_GSS);
                         WRITE32(info.oid.len);
                         WRITEMEM(info.oid.data, info.oid.len);
@@ -3292,7 +3363,9 @@ nfsd4_do_encode_secinfo(struct nfsd4_compoundres *resp,
                         WRITE32(info.service);
                 } else if (pf < RPC_AUTH_MAXFLAVOR) {
                         supported++;
-                        RESERVE_SPACE(4);
+                        p = xdr_reserve_space(xdr, 4);
+                        if (!p)
+                                goto out;
                         WRITE32(pf);
                 } else {
                         if (report)
@@ -3304,7 +3377,7 @@ nfsd4_do_encode_secinfo(struct nfsd4_compoundres *resp,
         if (nflavs != supported)
                 report = false;
         *flavorsp = htonl(supported);
-
+        nfserr = 0;
 out:
         if (exp)
                 exp_put(exp);
@@ -3315,14 +3388,18 @@ static __be32
 nfsd4_encode_secinfo(struct nfsd4_compoundres *resp, __be32 nfserr,
                      struct nfsd4_secinfo *secinfo)
 {
-        return nfsd4_do_encode_secinfo(resp, nfserr, secinfo->si_exp);
+        struct xdr_stream *xdr = &resp->xdr;
+
+        return nfsd4_do_encode_secinfo(xdr, nfserr, secinfo->si_exp);
 }
 
 static __be32
 nfsd4_encode_secinfo_no_name(struct nfsd4_compoundres *resp, __be32 nfserr,
                      struct nfsd4_secinfo_no_name *secinfo)
 {
-        return nfsd4_do_encode_secinfo(resp, nfserr, secinfo->sin_exp);
+        struct xdr_stream *xdr = &resp->xdr;
+
+        return nfsd4_do_encode_secinfo(xdr, nfserr, secinfo->sin_exp);
 }
 
 /*
@@ -3332,9 +3409,12 @@ nfsd4_encode_secinfo_no_name(struct nfsd4_compoundres *resp, __be32 nfserr,
 static __be32
 nfsd4_encode_setattr(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_setattr *setattr)
 {
+        struct xdr_stream *xdr = &resp->xdr;
         __be32 *p;
 
-        RESERVE_SPACE(16);
+        p = xdr_reserve_space(xdr, 16);
+        if (!p)
+                return nfserr_resource;
         if (nfserr) {
                 WRITE32(3);
                 WRITE32(0);
@@ -3353,15 +3433,20 @@ nfsd4_encode_setattr(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4
 static __be32
 nfsd4_encode_setclientid(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_setclientid *scd)
 {
+        struct xdr_stream *xdr = &resp->xdr;
         __be32 *p;
 
         if (!nfserr) {
-                RESERVE_SPACE(8 + NFS4_VERIFIER_SIZE);
+                p = xdr_reserve_space(xdr, 8 + NFS4_VERIFIER_SIZE);
+                if (!p)
+                        return nfserr_resource;
                 WRITEMEM(&scd->se_clientid, 8);
                 WRITEMEM(&scd->se_confirm, NFS4_VERIFIER_SIZE);
         }
         else if (nfserr == nfserr_clid_inuse) {
-                RESERVE_SPACE(8);
+                p = xdr_reserve_space(xdr, 8);
+                if (!p)
+                        return nfserr_resource;
                 WRITE32(0);
                 WRITE32(0);
         }
@@ -3371,10 +3456,13 @@ nfsd4_encode_setclientid(struct nfsd4_compoundres *resp, __be32 nfserr, struct n
 static __be32
 nfsd4_encode_write(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_write *write)
 {
+        struct xdr_stream *xdr = &resp->xdr;
         __be32 *p;
 
         if (!nfserr) {
-                RESERVE_SPACE(16);
+                p = xdr_reserve_space(xdr, 16);
+                if (!p)
+                        return nfserr_resource;
                 WRITE32(write->wr_bytes_written);
                 WRITE32(write->wr_how_written);
                 WRITEMEM(write->wr_verifier.data, NFS4_VERIFIER_SIZE);
@@ -3394,6 +3482,7 @@ static __be32
 nfsd4_encode_exchange_id(struct nfsd4_compoundres *resp, __be32 nfserr,
                          struct nfsd4_exchange_id *exid)
 {
+        struct xdr_stream *xdr = &resp->xdr;
         __be32 *p;
         char *major_id;
         char *server_scope;
@@ -3409,11 +3498,13 @@ nfsd4_encode_exchange_id(struct nfsd4_compoundres *resp, __be32 nfserr,
         server_scope = utsname()->nodename;
         server_scope_sz = strlen(server_scope);
 
-        RESERVE_SPACE(
+        p = xdr_reserve_space(xdr,
                 8 /* eir_clientid */ +
                 4 /* eir_sequenceid */ +
                 4 /* eir_flags */ +
                 4 /* spr_how */);
+        if (!p)
+                return nfserr_resource;
 
         WRITEMEM(&exid->clientid, 8);
         WRITE32(exid->seqid);
@@ -3426,7 +3517,9 @@ nfsd4_encode_exchange_id(struct nfsd4_compoundres *resp, __be32 nfserr,
                 break;
         case SP4_MACH_CRED:
                 /* spo_must_enforce, spo_must_allow */
-                RESERVE_SPACE(16);
+                p = xdr_reserve_space(xdr, 16);
+                if (!p)
+                        return nfserr_resource;
 
                 /* spo_must_enforce bitmap: */
                 WRITE32(2);
@@ -3440,13 +3533,15 @@ nfsd4_encode_exchange_id(struct nfsd4_compoundres *resp, __be32 nfserr,
                 WARN_ON_ONCE(1);
         }
 
-        RESERVE_SPACE(
+        p = xdr_reserve_space(xdr,
                 8 /* so_minor_id */ +
                 4 /* so_major_id.len */ +
                 (XDR_QUADLEN(major_id_sz) * 4) +
                 4 /* eir_server_scope.len */ +
                 (XDR_QUADLEN(server_scope_sz) * 4) +
                 4 /* eir_server_impl_id.count (0) */);
+        if (!p)
+                return nfserr_resource;
 
         /* The server_owner struct */
         WRITE64(minor_id);      /* Minor id */
@@ -3467,17 +3562,22 @@ static __be32
 nfsd4_encode_create_session(struct nfsd4_compoundres *resp, __be32 nfserr,
                             struct nfsd4_create_session *sess)
 {
+        struct xdr_stream *xdr = &resp->xdr;
         __be32 *p;
 
         if (nfserr)
                 return nfserr;
 
-        RESERVE_SPACE(24);
+        p = xdr_reserve_space(xdr, 24);
+        if (!p)
+                return nfserr_resource;
         WRITEMEM(sess->sessionid.data, NFS4_MAX_SESSIONID_LEN);
         WRITE32(sess->seqid);
         WRITE32(sess->flags);
 
-        RESERVE_SPACE(28);
+        p = xdr_reserve_space(xdr, 28);
+        if (!p)
+                return nfserr_resource;
         WRITE32(0); /* headerpadsz */
         WRITE32(sess->fore_channel.maxreq_sz);
         WRITE32(sess->fore_channel.maxresp_sz);
@@ -3487,11 +3587,15 @@ nfsd4_encode_create_session(struct nfsd4_compoundres *resp, __be32 nfserr,
         WRITE32(sess->fore_channel.nr_rdma_attrs);
 
         if (sess->fore_channel.nr_rdma_attrs) {
-                RESERVE_SPACE(4);
+                p = xdr_reserve_space(xdr, 4);
+                if (!p)
+                        return nfserr_resource;
                 WRITE32(sess->fore_channel.rdma_attrs);
         }
 
-        RESERVE_SPACE(28);
+        p = xdr_reserve_space(xdr, 28);
+        if (!p)
+                return nfserr_resource;
         WRITE32(0); /* headerpadsz */
         WRITE32(sess->back_channel.maxreq_sz);
         WRITE32(sess->back_channel.maxresp_sz);
@@ -3501,7 +3605,9 @@ nfsd4_encode_create_session(struct nfsd4_compoundres *resp, __be32 nfserr,
         WRITE32(sess->back_channel.nr_rdma_attrs);
 
         if (sess->back_channel.nr_rdma_attrs) {
-                RESERVE_SPACE(4);
+                p = xdr_reserve_space(xdr, 4);
+                if (!p)
+                        return nfserr_resource;
                 WRITE32(sess->back_channel.rdma_attrs);
         }
         return 0;
@@ -3511,12 +3617,15 @@ static __be32
 nfsd4_encode_sequence(struct nfsd4_compoundres *resp, __be32 nfserr,
                       struct nfsd4_sequence *seq)
 {
+        struct xdr_stream *xdr = &resp->xdr;
         __be32 *p;
 
         if (nfserr)
                 return nfserr;
 
-        RESERVE_SPACE(NFS4_MAX_SESSIONID_LEN + 20);
+        p = xdr_reserve_space(xdr, NFS4_MAX_SESSIONID_LEN + 20);
+        if (!p)
+                return nfserr_resource;
         WRITEMEM(seq->sessionid.data, NFS4_MAX_SESSIONID_LEN);
         WRITE32(seq->seqid);
         WRITE32(seq->slotid);
@@ -3533,13 +3642,16 @@ static __be32
 nfsd4_encode_test_stateid(struct nfsd4_compoundres *resp, __be32 nfserr,
                           struct nfsd4_test_stateid *test_stateid)
 {
+        struct xdr_stream *xdr = &resp->xdr;
         struct nfsd4_test_stateid_id *stateid, *next;
         __be32 *p;
 
         if (nfserr)
                 return nfserr;
 
-        RESERVE_SPACE(4 + (4 * test_stateid->ts_num_ids));
+        p = xdr_reserve_space(xdr, 4 + (4 * test_stateid->ts_num_ids));
+        if (!p)
+                return nfserr_resource;
         *p++ = htonl(test_stateid->ts_num_ids);
 
         list_for_each_entry_safe(stateid, next, &test_stateid->ts_stateid_list, ts_id_list) {
@@ -3678,7 +3790,11 @@ nfsd4_encode_operation(struct nfsd4_compoundres *resp, struct nfsd4_op *op)
         nfsd4_enc encoder;
         __be32 *p;
 
-        RESERVE_SPACE(8);
+        p = xdr_reserve_space(xdr, 8);
+        if (!p) {
+                WARN_ON_ONCE(1);
+                return;
+        }
         WRITE32(op->opnum);
         post_err_offset = xdr->buf->len;
 
@@ -3730,18 +3846,21 @@ status:
  * called with nfs4_lock_state() held
  */
 void
-nfsd4_encode_replay(struct nfsd4_compoundres *resp, struct nfsd4_op *op)
+nfsd4_encode_replay(struct xdr_stream *xdr, struct nfsd4_op *op)
 {
         __be32 *p;
         struct nfs4_replay *rp = op->replay;
 
         BUG_ON(!rp);
 
-        RESERVE_SPACE(8);
+        p = xdr_reserve_space(xdr, 8 + rp->rp_buflen);
+        if (!p) {
+                WARN_ON_ONCE(1);
+                return;
+        }
         WRITE32(op->opnum);
         *p++ = rp->rp_status;  /* already xdr'ed */
 
-        RESERVE_SPACE(rp->rp_buflen);
         WRITEMEM(rp->rp_buf, rp->rp_buflen);
 }
 
diff --git a/fs/nfsd/xdr4.h b/fs/nfsd/xdr4.h
index 15ca47797a82..ea5ad5db655b 100644
--- a/fs/nfsd/xdr4.h
+++ b/fs/nfsd/xdr4.h
@@ -563,7 +563,7 @@ int nfs4svc_encode_compoundres(struct svc_rqst *, __be32 *,
                 struct nfsd4_compoundres *);
 __be32 nfsd4_check_resp_size(struct nfsd4_compoundres *, u32);
 void nfsd4_encode_operation(struct nfsd4_compoundres *, struct nfsd4_op *);
-void nfsd4_encode_replay(struct nfsd4_compoundres *resp, struct nfsd4_op *op);
+void nfsd4_encode_replay(struct xdr_stream *xdr, struct nfsd4_op *op);
 __be32 nfsd4_encode_fattr_to_buf(__be32 **p, int words,
                 struct svc_fh *fhp, struct svc_export *exp,
                 struct dentry *dentry,