SUNRPC: RPC buffer size estimates are too large

The RPC buffer size estimation logic in net/sunrpc/clnt.c always
significantly overestimates the requirements for the buffer size.
A little instrumentation demonstrated that in fact rpc_malloc was never
allocating the buffer from the mempool, but almost always called kmalloc.

To compute the size of the RPC buffer more precisely, split p_bufsiz into
two fields; one for the argument size, and one for the result size.

Then, compute the sum of the exact call and reply header sizes, and split
the RPC buffer precisely between the two.  That should keep almost all RPC
buffers within the 2KiB buffer mempool limit.

And, we can finally be rid of RPC_SLACK_SPACE!

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

13 files changed, 74 insertions, 70 deletions

diff --git a/fs/lockd/mon.c b/fs/lockd/mon.c
index eb243edf8932..2102e2d0134d 100644
--- a/fs/lockd/mon.c
+++ b/fs/lockd/mon.c
@@ -225,16 +225,13 @@ xdr_decode_stat(struct rpc_rqst *rqstp, __be32 *p, struct nsm_res *resp)
 #define SM_monres_sz    2
 #define SM_unmonres_sz  1
 
-#ifndef MAX
-# define MAX(a, b)      (((a) > (b))? (a) : (b))
-#endif
-
 static struct rpc_procinfo      nsm_procedures[] = {
 [SM_MON] = {
                 .p_proc         = SM_MON,
                 .p_encode       = (kxdrproc_t) xdr_encode_mon,
                 .p_decode       = (kxdrproc_t) xdr_decode_stat_res,
-                .p_bufsiz       = MAX(SM_mon_sz, SM_monres_sz) << 2,
+                .p_arglen       = SM_mon_sz,
+                .p_replen       = SM_monres_sz,
                 .p_statidx      = SM_MON,
                 .p_name         = "MONITOR",
         },
@@ -242,7 +239,8 @@ static struct rpc_procinfo	nsm_procedures[] = {
                 .p_proc         = SM_UNMON,
                 .p_encode       = (kxdrproc_t) xdr_encode_unmon,
                 .p_decode       = (kxdrproc_t) xdr_decode_stat,
-                .p_bufsiz       = MAX(SM_mon_id_sz, SM_unmonres_sz) << 2,
+                .p_arglen       = SM_mon_id_sz,
+                .p_replen       = SM_unmonres_sz,
                 .p_statidx      = SM_UNMON,
                 .p_name         = "UNMONITOR",
         },
diff --git a/fs/lockd/xdr.c b/fs/lockd/xdr.c
index 6aac4b2c9ff0..9702956d206c 100644
--- a/fs/lockd/xdr.c
+++ b/fs/lockd/xdr.c
@@ -534,10 +534,6 @@ nlmclt_decode_res(struct rpc_rqst *req, __be32 *p, struct nlm_res *resp)
 #define NLM_res_sz              NLM_cookie_sz+1
 #define NLM_norep_sz            0
 
-#ifndef MAX
-# define MAX(a, b)              (((a) > (b))? (a) : (b))
-#endif
-
 /*
  * For NLM, a void procedure really returns nothing
  */
@@ -548,7 +544,8 @@ nlmclt_decode_res(struct rpc_rqst *req, __be32 *p, struct nlm_res *resp)
         .p_proc      = NLMPROC_##proc,                                  \
         .p_encode    = (kxdrproc_t) nlmclt_encode_##argtype,            \
         .p_decode    = (kxdrproc_t) nlmclt_decode_##restype,            \
-        .p_bufsiz    = MAX(NLM_##argtype##_sz, NLM_##restype##_sz) << 2,        \
+        .p_arglen    = NLM_##argtype##_sz,                              \
+        .p_replen    = NLM_##restype##_sz,                              \
         .p_statidx   = NLMPROC_##proc,                                  \
         .p_name      = #proc,                                           \
         }
diff --git a/fs/lockd/xdr4.c b/fs/lockd/xdr4.c
index 7c8b679c394c..ce1efdbe1b3a 100644
--- a/fs/lockd/xdr4.c
+++ b/fs/lockd/xdr4.c
@@ -544,10 +544,6 @@ nlm4clt_decode_res(struct rpc_rqst *req, __be32 *p, struct nlm_res *resp)
 #define NLM4_res_sz             NLM4_cookie_sz+1
 #define NLM4_norep_sz           0
 
-#ifndef MAX
-# define MAX(a,b)               (((a) > (b))? (a) : (b))
-#endif
-
 /*
  * For NLM, a void procedure really returns nothing
  */
@@ -558,7 +554,8 @@ nlm4clt_decode_res(struct rpc_rqst *req, __be32 *p, struct nlm_res *resp)
         .p_proc      = NLMPROC_##proc,                                  \
         .p_encode    = (kxdrproc_t) nlm4clt_encode_##argtype,           \
         .p_decode    = (kxdrproc_t) nlm4clt_decode_##restype,           \
-        .p_bufsiz    = MAX(NLM4_##argtype##_sz, NLM4_##restype##_sz) << 2,      \
+        .p_arglen    = NLM4_##argtype##_sz,                             \
+        .p_replen    = NLM4_##restype##_sz,                             \
         .p_statidx   = NLMPROC_##proc,                                  \
         .p_name      = #proc,                                           \
         }
diff --git a/fs/nfs/mount_clnt.c b/fs/nfs/mount_clnt.c
index f75fe72b4160..ca5a266a3140 100644
--- a/fs/nfs/mount_clnt.c
+++ b/fs/nfs/mount_clnt.c
@@ -133,13 +133,15 @@ xdr_decode_fhstatus3(struct rpc_rqst *req, __be32 *p, struct mnt_fhstatus *res)
 
 #define MNT_dirpath_sz          (1 + 256)
 #define MNT_fhstatus_sz         (1 + 8)
+#define MNT_fhstatus3_sz        (1 + 16)
 
 static struct rpc_procinfo      mnt_procedures[] = {
 [MNTPROC_MNT] = {
           .p_proc               = MNTPROC_MNT,
           .p_encode             = (kxdrproc_t) xdr_encode_dirpath,      
           .p_decode             = (kxdrproc_t) xdr_decode_fhstatus,
-          .p_bufsiz             = MNT_dirpath_sz << 2,
+          .p_arglen             = MNT_dirpath_sz,
+          .p_replen             = MNT_fhstatus_sz,
           .p_statidx            = MNTPROC_MNT,
           .p_name               = "MOUNT",
         },
@@ -150,7 +152,8 @@ static struct rpc_procinfo mnt3_procedures[] = {
           .p_proc               = MOUNTPROC3_MNT,
           .p_encode             = (kxdrproc_t) xdr_encode_dirpath,
           .p_decode             = (kxdrproc_t) xdr_decode_fhstatus3,
-          .p_bufsiz             = MNT_dirpath_sz << 2,
+          .p_arglen             = MNT_dirpath_sz,
+          .p_replen             = MNT_fhstatus3_sz,
           .p_statidx            = MOUNTPROC3_MNT,
           .p_name               = "MOUNT",
         },
diff --git a/fs/nfs/nfs2xdr.c b/fs/nfs/nfs2xdr.c
index 3be4e72a0227..abd9f8b48943 100644
--- a/fs/nfs/nfs2xdr.c
+++ b/fs/nfs/nfs2xdr.c
@@ -687,16 +687,13 @@ nfs_stat_to_errno(int stat)
         return nfs_errtbl[i].errno;
 }
 
-#ifndef MAX
-# define MAX(a, b)      (((a) > (b))? (a) : (b))
-#endif
-
 #define PROC(proc, argtype, restype, timer)                             \
 [NFSPROC_##proc] = {                                                    \
         .p_proc     =  NFSPROC_##proc,                                  \
         .p_encode   =  (kxdrproc_t) nfs_xdr_##argtype,                  \
         .p_decode   =  (kxdrproc_t) nfs_xdr_##restype,                  \
-        .p_bufsiz   =  MAX(NFS_##argtype##_sz,NFS_##restype##_sz) << 2, \
+        .p_arglen   =  NFS_##argtype##_sz,                              \
+        .p_replen   =  NFS_##restype##_sz,                              \
         .p_timer    =  timer,                                           \
         .p_statidx  =  NFSPROC_##proc,                                  \
         .p_name     =  #proc,                                           \
diff --git a/fs/nfs/nfs3xdr.c b/fs/nfs/nfs3xdr.c
index 0ace092d126f..b51df8eb9f01 100644
--- a/fs/nfs/nfs3xdr.c
+++ b/fs/nfs/nfs3xdr.c
@@ -1102,16 +1102,13 @@ nfs3_xdr_setaclres(struct rpc_rqst *req, __be32 *p, struct nfs_fattr *fattr)
 }
 #endif  /* CONFIG_NFS_V3_ACL */
 
-#ifndef MAX
-# define MAX(a, b)      (((a) > (b))? (a) : (b))
-#endif
-
 #define PROC(proc, argtype, restype, timer)                             \
 [NFS3PROC_##proc] = {                                                   \
         .p_proc      = NFS3PROC_##proc,                                 \
         .p_encode    = (kxdrproc_t) nfs3_xdr_##argtype,                 \
         .p_decode    = (kxdrproc_t) nfs3_xdr_##restype,                 \
-        .p_bufsiz    = MAX(NFS3_##argtype##_sz,NFS3_##restype##_sz) << 2,       \
+        .p_arglen    = NFS3_##argtype##_sz,                             \
+        .p_replen    = NFS3_##restype##_sz,                             \
         .p_timer     = timer,                                           \
         .p_statidx   = NFS3PROC_##proc,                                 \
         .p_name      = #proc,                                           \
@@ -1153,7 +1150,8 @@ static struct rpc_procinfo	nfs3_acl_procedures[] = {
                 .p_proc = ACLPROC3_GETACL,
                 .p_encode = (kxdrproc_t) nfs3_xdr_getaclargs,
                 .p_decode = (kxdrproc_t) nfs3_xdr_getaclres,
-                .p_bufsiz = MAX(ACL3_getaclargs_sz, ACL3_getaclres_sz) << 2,
+                .p_arglen = ACL3_getaclargs_sz,
+                .p_replen = ACL3_getaclres_sz,
                 .p_timer = 1,
                 .p_name = "GETACL",
         },
@@ -1161,7 +1159,8 @@ static struct rpc_procinfo	nfs3_acl_procedures[] = {
                 .p_proc = ACLPROC3_SETACL,
                 .p_encode = (kxdrproc_t) nfs3_xdr_setaclargs,
                 .p_decode = (kxdrproc_t) nfs3_xdr_setaclres,
-                .p_bufsiz = MAX(ACL3_setaclargs_sz, ACL3_setaclres_sz) << 2,
+                .p_arglen = ACL3_setaclargs_sz,
+                .p_replen = ACL3_setaclres_sz,
                 .p_timer = 0,
                 .p_name = "SETACL",
         },
diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
index f02d522fd788..b8c28f2380a5 100644
--- a/fs/nfs/nfs4xdr.c
+++ b/fs/nfs/nfs4xdr.c
@@ -4546,16 +4546,13 @@ nfs4_stat_to_errno(int stat)
         return stat;
 }
 
-#ifndef MAX
-# define MAX(a, b)      (((a) > (b))? (a) : (b))
-#endif
-
 #define PROC(proc, argtype, restype)                            \
 [NFSPROC4_CLNT_##proc] = {                                      \
         .p_proc   = NFSPROC4_COMPOUND,                          \
         .p_encode = (kxdrproc_t) nfs4_xdr_##argtype,            \
         .p_decode = (kxdrproc_t) nfs4_xdr_##restype,            \
-        .p_bufsiz = MAX(NFS4_##argtype##_sz,NFS4_##restype##_sz) << 2,  \
+        .p_arglen = NFS4_##argtype##_sz,                        \
+        .p_replen = NFS4_##restype##_sz,                        \
         .p_statidx = NFSPROC4_CLNT_##proc,                      \
         .p_name   = #proc,                                      \
     }
diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
index fb14d68eacab..32ffea033c7a 100644
--- a/fs/nfsd/nfs4callback.c
+++ b/fs/nfsd/nfs4callback.c
@@ -315,16 +315,13 @@ out:
 /*
  * RPC procedure tables
  */
-#ifndef MAX
-# define MAX(a, b)      (((a) > (b))? (a) : (b))
-#endif
-
 #define PROC(proc, call, argtype, restype)                              \
 [NFSPROC4_CLNT_##proc] = {                                              \
         .p_proc   = NFSPROC4_CB_##call,                                 \
         .p_encode = (kxdrproc_t) nfs4_xdr_##argtype,                    \
         .p_decode = (kxdrproc_t) nfs4_xdr_##restype,                    \
-        .p_bufsiz = MAX(NFS4_##argtype##_sz,NFS4_##restype##_sz) << 2,  \
+        .p_arglen = NFS4_##argtype##_sz,                                \
+        .p_replen = NFS4_##restype##_sz,                                \
         .p_statidx = NFSPROC4_CB_##call,                                \
         .p_name   = #proc,                                              \
 }
diff --git a/include/linux/sunrpc/clnt.h b/include/linux/sunrpc/clnt.h
index c7a78eef2b4f..32c48a0b0d71 100644
--- a/include/linux/sunrpc/clnt.h
+++ b/include/linux/sunrpc/clnt.h
@@ -84,7 +84,8 @@ struct rpc_procinfo {
         u32                     p_proc;         /* RPC procedure number */
         kxdrproc_t              p_encode;       /* XDR encode function */
         kxdrproc_t              p_decode;       /* XDR decode function */
-        unsigned int            p_bufsiz;       /* req. buffer size */
+        unsigned int            p_arglen;       /* argument hdr length (u32) */
+        unsigned int            p_replen;       /* reply hdr length (u32) */
         unsigned int            p_count;        /* call count */
         unsigned int            p_timer;        /* Which RTT timer to use */
         u32                     p_statidx;      /* Which procedure to account */
diff --git a/include/linux/sunrpc/xprt.h b/include/linux/sunrpc/xprt.h
index f780e72fc417..7aa29502b187 100644
--- a/include/linux/sunrpc/xprt.h
+++ b/include/linux/sunrpc/xprt.h
@@ -84,7 +84,9 @@ struct rpc_rqst {
         struct list_head        rq_list;
 
         __u32 *                 rq_buffer;      /* XDR encode buffer */
-        size_t                  rq_bufsize;
+        size_t                  rq_bufsize,
+                                rq_callsize,
+                                rq_rcvsize;
 
         struct xdr_buf          rq_private_buf;         /* The receive buffer
                                                          * used in the softirq.
diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index 396cdbe249d1..12487aafaab5 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -36,8 +36,6 @@
 #include <linux/sunrpc/metrics.h>
 
 
-#define RPC_SLACK_SPACE         (1024)  /* total overkill */
-
 #ifdef RPC_DEBUG
 # define RPCDBG_FACILITY        RPCDBG_CALL
 #endif
@@ -747,21 +745,37 @@ call_reserveresult(struct rpc_task *task)
 static void
 call_allocate(struct rpc_task *task)
 {
+        unsigned int slack = task->tk_auth->au_cslack;
         struct rpc_rqst *req = task->tk_rqstp;
         struct rpc_xprt *xprt = task->tk_xprt;
-        unsigned int    bufsiz;
+        struct rpc_procinfo *proc = task->tk_msg.rpc_proc;
 
         dprint_status(task);
 
+        task->tk_status = 0;
         task->tk_action = call_bind;
+
         if (req->rq_buffer)
                 return;
 
-        /* FIXME: compute buffer requirements more exactly using
-         * auth->au_wslack */
-        bufsiz = task->tk_msg.rpc_proc->p_bufsiz + RPC_SLACK_SPACE;
+        if (proc->p_proc != 0) {
+                BUG_ON(proc->p_arglen == 0);
+                if (proc->p_decode != NULL)
+                        BUG_ON(proc->p_replen == 0);
+        }
 
-        if (xprt->ops->buf_alloc(task, bufsiz << 1) != NULL)
+        /*
+         * Calculate the size (in quads) of the RPC call
+         * and reply headers, and convert both values
+         * to byte sizes.
+         */
+        req->rq_callsize = RPC_CALLHDRSIZE + (slack << 1) + proc->p_arglen;
+        req->rq_callsize <<= 2;
+        req->rq_rcvsize = RPC_REPHDRSIZE + slack + proc->p_replen;
+        req->rq_rcvsize <<= 2;
+
+        xprt->ops->buf_alloc(task, req->rq_callsize + req->rq_rcvsize);
+        if (req->rq_buffer != NULL)
                 return;
 
         dprintk("RPC: %5u rpc_buffer allocation failed\n", task->tk_pid);
@@ -788,6 +802,17 @@ rpc_task_force_reencode(struct rpc_task *task)
         task->tk_rqstp->rq_snd_buf.len = 0;
 }
 
+static inline void
+rpc_xdr_buf_init(struct xdr_buf *buf, void *start, size_t len)
+{
+        buf->head[0].iov_base = start;
+        buf->head[0].iov_len = len;
+        buf->tail[0].iov_len = 0;
+        buf->page_len = 0;
+        buf->len = 0;
+        buf->buflen = len;
+}
+
 /*
  * 3.   Encode arguments of an RPC call
  */
@@ -795,28 +820,17 @@ static void
 call_encode(struct rpc_task *task)
 {
         struct rpc_rqst *req = task->tk_rqstp;
-        struct xdr_buf *sndbuf = &req->rq_snd_buf;
-        struct xdr_buf *rcvbuf = &req->rq_rcv_buf;
-        unsigned int    bufsiz;
         kxdrproc_t      encode;
         __be32          *p;
 
         dprint_status(task);
 
-        /* Default buffer setup */
-        bufsiz = req->rq_bufsize >> 1;
-        sndbuf->head[0].iov_base = (void *)req->rq_buffer;
-        sndbuf->head[0].iov_len  = bufsiz;
-        sndbuf->tail[0].iov_len  = 0;
-        sndbuf->page_len         = 0;
-        sndbuf->len              = 0;
-        sndbuf->buflen           = bufsiz;
-        rcvbuf->head[0].iov_base = (void *)((char *)req->rq_buffer + bufsiz);
-        rcvbuf->head[0].iov_len  = bufsiz;
-        rcvbuf->tail[0].iov_len  = 0;
-        rcvbuf->page_len         = 0;
-        rcvbuf->len              = 0;
-        rcvbuf->buflen           = bufsiz;
+        rpc_xdr_buf_init(&req->rq_snd_buf,
+                         req->rq_buffer,
+                         req->rq_callsize);
+        rpc_xdr_buf_init(&req->rq_rcv_buf,
+                         (char *)req->rq_buffer + req->rq_callsize,
+                         req->rq_rcvsize);
 
         /* Encode header and provided arguments */
         encode = task->tk_msg.rpc_proc->p_encode;
diff --git a/net/sunrpc/pmap_clnt.c b/net/sunrpc/pmap_clnt.c
index d9f765344589..c45fc4c99513 100644
--- a/net/sunrpc/pmap_clnt.c
+++ b/net/sunrpc/pmap_clnt.c
@@ -335,7 +335,8 @@ static struct rpc_procinfo	pmap_procedures[] = {
           .p_proc               = PMAP_SET,
           .p_encode             = (kxdrproc_t) xdr_encode_mapping,
           .p_decode             = (kxdrproc_t) xdr_decode_bool,
-          .p_bufsiz             = 4,
+          .p_arglen             = 4,
+          .p_replen             = 1,
           .p_count              = 1,
           .p_statidx            = PMAP_SET,
           .p_name               = "SET",
@@ -344,7 +345,8 @@ static struct rpc_procinfo	pmap_procedures[] = {
           .p_proc               = PMAP_UNSET,
           .p_encode             = (kxdrproc_t) xdr_encode_mapping,
           .p_decode             = (kxdrproc_t) xdr_decode_bool,
-          .p_bufsiz             = 4,
+          .p_arglen             = 4,
+          .p_replen             = 1,
           .p_count              = 1,
           .p_statidx            = PMAP_UNSET,
           .p_name               = "UNSET",
@@ -353,7 +355,8 @@ static struct rpc_procinfo	pmap_procedures[] = {
           .p_proc               = PMAP_GETPORT,
           .p_encode             = (kxdrproc_t) xdr_encode_mapping,
           .p_decode             = (kxdrproc_t) xdr_decode_port,
-          .p_bufsiz             = 4,
+          .p_arglen             = 4,
+          .p_replen             = 1,
           .p_count              = 1,
           .p_statidx            = PMAP_GETPORT,
           .p_name               = "GETPORT",
diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
index 456a14510308..432ee92cf262 100644
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -823,7 +823,6 @@ static void xprt_request_init(struct rpc_task *task, struct rpc_xprt *xprt)
         req->rq_task    = task;
         req->rq_xprt    = xprt;
         req->rq_buffer  = NULL;
-        req->rq_bufsize = 0;
         req->rq_xid     = xprt_alloc_xid(xprt);
         req->rq_release_snd_buf = NULL;
         xprt_reset_majortimeo(req);