[PATCH] v9fs: zero copy implementation

Performance enhancement reducing the number of copies in the data and
stat paths.

Signed-off-by: Latchesar Ionkov <lucho@ionkov.net>
Cc: Eric Van Hensbergen <ericvh@ericvh.myip.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 518 insertions, 377 deletions

diff --git a/fs/9p/conv.c b/fs/9p/conv.c
index 1b9b15dfeaf0..f62434d435b3 100644
--- a/fs/9p/conv.c
+++ b/fs/9p/conv.c
@@ -30,7 +30,7 @@
 #include <linux/errno.h>
 #include <linux/fs.h>
 #include <linux/idr.h>
-
+#include <asm/uaccess.h>
 #include "debug.h"
 #include "v9fs.h"
 #include "9p.h"
@@ -45,6 +45,37 @@ struct cbuf {
         unsigned char *ep;
 };
 
+char *v9fs_str_copy(char *buf, int buflen, struct v9fs_str *str)
+{
+        int n;
+
+        if (buflen < str->len)
+                n = buflen;
+        else
+                n = str->len;
+
+        memmove(buf, str->str, n - 1);
+
+        return buf;
+}
+
+int v9fs_str_compare(char *buf, struct v9fs_str *str)
+{
+        int n, ret;
+
+        ret = strncmp(buf, str->str, str->len);
+
+        if (!ret) {
+                n = strlen(buf);
+                if (n < str->len)
+                        ret = -1;
+                else if (n > str->len)
+                        ret = 1;
+        }
+
+        return ret;
+}
+
 static inline void buf_init(struct cbuf *buf, void *data, int datalen)
 {
         buf->sp = buf->p = data;
@@ -58,12 +89,12 @@ static inline int buf_check_overflow(struct cbuf *buf)
 
 static inline int buf_check_size(struct cbuf *buf, int len)
 {
-        if (buf->p+len > buf->ep) {
-                if (buf->p < buf->ep) {
-                        eprintk(KERN_ERR, "buffer overflow\n");
-                        buf->p = buf->ep + 1;
-                        return 0;
-                }
+        if (buf->p + len > buf->ep && buf->p < buf->ep) {
+                eprintk(KERN_ERR, "buffer overflow: want %d has %d\n",
+                        len, (int)(buf->ep - buf->p));
+                dump_stack();
+                buf->p = buf->ep + 1;
+                return 0;
         }
 
         return 1;
@@ -127,14 +158,6 @@ static inline void buf_put_string(struct cbuf *buf, const char *s)
         buf_put_stringn(buf, s, strlen(s));
 }
 
-static inline void buf_put_data(struct cbuf *buf, void *data, u32 datalen)
-{
-        if (buf_check_size(buf, datalen)) {
-                memcpy(buf->p, data, datalen);
-                buf->p += datalen;
-        }
-}
-
 static inline u8 buf_get_int8(struct cbuf *buf)
 {
         u8 ret = 0;
@@ -183,85 +206,37 @@ static inline u64 buf_get_int64(struct cbuf *buf)
         return ret;
 }
 
-static inline int
-buf_get_string(struct cbuf *buf, char *data, unsigned int datalen)
-{
-        u16 len = 0;
-
-        len = buf_get_int16(buf);
-        if (!buf_check_overflow(buf) && buf_check_size(buf, len) && len+1>datalen) {
-                memcpy(data, buf->p, len);
-                data[len] = 0;
-                buf->p += len;
-                len++;
-        }
-
-        return len;
-}
-
-static inline char *buf_get_stringb(struct cbuf *buf, struct cbuf *sbuf)
-{
-        char *ret;
-        u16 len;
-
-        ret = NULL;
-        len = buf_get_int16(buf);
-
-        if (!buf_check_overflow(buf) && buf_check_size(buf, len) &&
-                buf_check_size(sbuf, len + 1)) {
-
-                memcpy(sbuf->p, buf->p, len);
-                sbuf->p[len] = 0;
-                ret = sbuf->p;
-                buf->p += len;
-                sbuf->p += len + 1;
-        }
-
-        return ret;
-}
-
-static inline int buf_get_data(struct cbuf *buf, void *data, int datalen)
+static inline void buf_get_str(struct cbuf *buf, struct v9fs_str *vstr)
 {
-        int ret = 0;
-
-        if (buf_check_size(buf, datalen)) {
-                memcpy(data, buf->p, datalen);
-                buf->p += datalen;
-                ret = datalen;
+        vstr->len = buf_get_int16(buf);
+        if (!buf_check_overflow(buf) && buf_check_size(buf, vstr->len)) {
+                vstr->str = buf->p;
+                buf->p += vstr->len;
+        } else {
+                vstr->len = 0;
+                vstr->str = NULL;
         }
-
-        return ret;
 }
 
-static inline void *buf_get_datab(struct cbuf *buf, struct cbuf *dbuf,
-                                  int datalen)
+static inline void buf_get_qid(struct cbuf *bufp, struct v9fs_qid *qid)
 {
-        char *ret = NULL;
-        int n = 0;
-
-        if (buf_check_size(dbuf, datalen)) {
-                n = buf_get_data(buf, dbuf->p, datalen);
-                if (n > 0) {
-                        ret = dbuf->p;
-                        dbuf->p += n;
-                }
-        }
-
-        return ret;
+        qid->type = buf_get_int8(bufp);
+        qid->version = buf_get_int32(bufp);
+        qid->path = buf_get_int64(bufp);
 }
 
 /**
- * v9fs_size_stat - calculate the size of a variable length stat struct
+ * v9fs_size_wstat - calculate the size of a variable length stat struct
  * @stat: metadata (stat) structure
  * @extended: non-zero if 9P2000.u
  *
  */
 
-static int v9fs_size_stat(struct v9fs_stat *stat, int extended)
+static int v9fs_size_wstat(struct v9fs_wstat *wstat, int extended)
 {
         int size = 0;
 
-        if (stat == NULL) {
+        if (wstat == NULL) {
                 eprintk(KERN_ERR, "v9fs_size_stat: got a NULL stat pointer\n");
                 return 0;
         }
@@ -278,81 +253,38 @@ static int v9fs_size_stat(struct v9fs_stat *stat, int extended)
             8 +                 /* length[8] */
             8;                  /* minimum sum of string lengths */
 
-        if (stat->name)
-                size += strlen(stat->name);
-        if (stat->uid)
-                size += strlen(stat->uid);
-        if (stat->gid)
-                size += strlen(stat->gid);
-        if (stat->muid)
-                size += strlen(stat->muid);
+        if (wstat->name)
+                size += strlen(wstat->name);
+        if (wstat->uid)
+                size += strlen(wstat->uid);
+        if (wstat->gid)
+                size += strlen(wstat->gid);
+        if (wstat->muid)
+                size += strlen(wstat->muid);
 
         if (extended) {
                 size += 4 +     /* n_uid[4] */
                     4 +         /* n_gid[4] */
                     4 +         /* n_muid[4] */
                     2;          /* string length of extension[4] */
-                if (stat->extension)
-                        size += strlen(stat->extension);
+                if (wstat->extension)
+                        size += strlen(wstat->extension);
         }
 
         return size;
 }
 
 /**
- * serialize_stat - safely format a stat structure for transmission
- * @stat: metadata (stat) structure
- * @bufp: buffer to serialize structure into
- * @extended: non-zero if 9P2000.u
- *
- */
-
-static int
-serialize_stat(struct v9fs_stat *stat, struct cbuf *bufp, int extended)
-{
-        buf_put_int16(bufp, stat->size);
-        buf_put_int16(bufp, stat->type);
-        buf_put_int32(bufp, stat->dev);
-        buf_put_int8(bufp, stat->qid.type);
-        buf_put_int32(bufp, stat->qid.version);
-        buf_put_int64(bufp, stat->qid.path);
-        buf_put_int32(bufp, stat->mode);
-        buf_put_int32(bufp, stat->atime);
-        buf_put_int32(bufp, stat->mtime);
-        buf_put_int64(bufp, stat->length);
-
-        buf_put_string(bufp, stat->name);
-        buf_put_string(bufp, stat->uid);
-        buf_put_string(bufp, stat->gid);
-        buf_put_string(bufp, stat->muid);
-
-        if (extended) {
-                buf_put_string(bufp, stat->extension);
-                buf_put_int32(bufp, stat->n_uid);
-                buf_put_int32(bufp, stat->n_gid);
-                buf_put_int32(bufp, stat->n_muid);
-        }
-
-        if (buf_check_overflow(bufp))
-                return 0;
-
-        return stat->size;
-}
-
-/**
- * deserialize_stat - safely decode a recieved metadata (stat) structure
+ * buf_get_stat - safely decode a recieved metadata (stat) structure
  * @bufp: buffer to deserialize
  * @stat: metadata (stat) structure
- * @dbufp: buffer to deserialize variable strings into
  * @extended: non-zero if 9P2000.u
  *
  */
 
-static inline int
-deserialize_stat(struct cbuf *bufp, struct v9fs_stat *stat,
-                 struct cbuf *dbufp, int extended)
+static inline void
+buf_get_stat(struct cbuf *bufp, struct v9fs_stat *stat, int extended)
 {
-
         stat->size = buf_get_int16(bufp);
         stat->type = buf_get_int16(bufp);
         stat->dev = buf_get_int32(bufp);
@@ -363,45 +295,17 @@ deserialize_stat(struct cbuf *bufp, struct v9fs_stat *stat,
         stat->atime = buf_get_int32(bufp);
         stat->mtime = buf_get_int32(bufp);
         stat->length = buf_get_int64(bufp);
-        stat->name = buf_get_stringb(bufp, dbufp);
-        stat->uid = buf_get_stringb(bufp, dbufp);
-        stat->gid = buf_get_stringb(bufp, dbufp);
-        stat->muid = buf_get_stringb(bufp, dbufp);
+        buf_get_str(bufp, &stat->name);
+        buf_get_str(bufp, &stat->uid);
+        buf_get_str(bufp, &stat->gid);
+        buf_get_str(bufp, &stat->muid);
 
         if (extended) {
-                stat->extension = buf_get_stringb(bufp, dbufp);
+                buf_get_str(bufp, &stat->extension);
                 stat->n_uid = buf_get_int32(bufp);
                 stat->n_gid = buf_get_int32(bufp);
                 stat->n_muid = buf_get_int32(bufp);
         }
-
-        if (buf_check_overflow(bufp) || buf_check_overflow(dbufp))
-                return 0;
-
-        return stat->size + 2;
-}
-
-/**
- * deserialize_statb - wrapper for decoding a received metadata structure
- * @bufp: buffer to deserialize
- * @dbufp: buffer to deserialize variable strings into
- * @extended: non-zero if 9P2000.u
- *
- */
-
-static inline struct v9fs_stat *deserialize_statb(struct cbuf *bufp,
-                                                  struct cbuf *dbufp,
-                                                  int extended)
-{
-        struct v9fs_stat *ret = buf_alloc(dbufp, sizeof(struct v9fs_stat));
-
-        if (ret) {
-                int n = deserialize_stat(bufp, ret, dbufp, extended);
-                if (n <= 0)
-                        return NULL;
-        }
-
-        return ret;
 }
 
 /**
@@ -409,194 +313,27 @@ static inline struct v9fs_stat *deserialize_statb(struct cbuf *bufp,
  * @buf: buffer to deserialize
  * @buflen: length of received buffer
  * @stat: metadata structure to decode into
- * @statlen: length of destination metadata structure
  * @extended: non-zero if 9P2000.u
  *
+ * Note: stat will point to the buf region.
  */
 
-int v9fs_deserialize_stat(void *buf, u32 buflen, struct v9fs_stat *stat,
-                          u32 statlen, int extended)
+int
+v9fs_deserialize_stat(void *buf, u32 buflen, struct v9fs_stat *stat,
+                int extended)
 {
         struct cbuf buffer;
         struct cbuf *bufp = &buffer;
-        struct cbuf dbuffer;
-        struct cbuf *dbufp = &dbuffer;
+        unsigned char *p;
 
         buf_init(bufp, buf, buflen);
-        buf_init(dbufp, (char *)stat + sizeof(struct v9fs_stat),
-                 statlen - sizeof(struct v9fs_stat));
-
-        return deserialize_stat(bufp, stat, dbufp, extended);
-}
-
-static inline int v9fs_size_fcall(struct v9fs_fcall *fcall, int extended)
-{
-        int size = 4 + 1 + 2;   /* size[4] msg[1] tag[2] */
-        int i = 0;
+        p = bufp->p;
+        buf_get_stat(bufp, stat, extended);
 
-        switch (fcall->id) {
-        default:
-                eprintk(KERN_ERR, "bad msg type %d\n", fcall->id);
+        if (buf_check_overflow(bufp))
                 return 0;
-        case TVERSION:          /* msize[4] version[s] */
-                size += 4 + 2 + strlen(fcall->params.tversion.version);
-                break;
-        case TAUTH:             /* afid[4] uname[s] aname[s] */
-                size += 4 + 2 + strlen(fcall->params.tauth.uname) +
-                    2 + strlen(fcall->params.tauth.aname);
-                break;
-        case TFLUSH:            /* oldtag[2] */
-                size += 2;
-                break;
-        case TATTACH:           /* fid[4] afid[4] uname[s] aname[s] */
-                size += 4 + 4 + 2 + strlen(fcall->params.tattach.uname) +
-                    2 + strlen(fcall->params.tattach.aname);
-                break;
-        case TWALK:             /* fid[4] newfid[4] nwname[2] nwname*(wname[s]) */
-                size += 4 + 4 + 2;
-                /* now compute total for the array of names */
-                for (i = 0; i < fcall->params.twalk.nwname; i++)
-                        size += 2 + strlen(fcall->params.twalk.wnames[i]);
-                break;
-        case TOPEN:             /* fid[4] mode[1] */
-                size += 4 + 1;
-                break;
-        case TCREATE:           /* fid[4] name[s] perm[4] mode[1] */
-                size += 4 + 2 + strlen(fcall->params.tcreate.name) + 4 + 1;
-                break;
-        case TREAD:             /* fid[4] offset[8] count[4] */
-                size += 4 + 8 + 4;
-                break;
-        case TWRITE:            /* fid[4] offset[8] count[4] data[count] */
-                size += 4 + 8 + 4 + fcall->params.twrite.count;
-                break;
-        case TCLUNK:            /* fid[4] */
-                size += 4;
-                break;
-        case TREMOVE:           /* fid[4] */
-                size += 4;
-                break;
-        case TSTAT:             /* fid[4] */
-                size += 4;
-                break;
-        case TWSTAT:            /* fid[4] stat[n] */
-                fcall->params.twstat.stat->size =
-                    v9fs_size_stat(fcall->params.twstat.stat, extended);
-                size += 4 + 2 + 2 + fcall->params.twstat.stat->size;
-        }
-        return size;
-}
-
-/*
- * v9fs_serialize_fcall - marshall fcall struct into a packet
- * @fcall: structure to convert
- * @data: buffer to serialize fcall into
- * @datalen: length of buffer to serialize fcall into
- * @extended: non-zero if 9P2000.u
- *
- */
-
-int
-v9fs_serialize_fcall(struct v9fs_fcall *fcall, void *data, u32 datalen,
-                     int extended)
-{
-        int i = 0;
-        struct v9fs_stat *stat = NULL;
-        struct cbuf buffer;
-        struct cbuf *bufp = &buffer;
-
-        buf_init(bufp, data, datalen);
-
-        if (!fcall) {
-                eprintk(KERN_ERR, "no fcall\n");
-                return -EINVAL;
-        }
-
-        fcall->size = v9fs_size_fcall(fcall, extended);
-
-        buf_put_int32(bufp, fcall->size);
-        buf_put_int8(bufp, fcall->id);
-        buf_put_int16(bufp, fcall->tag);
-
-        dprintk(DEBUG_CONV, "size %d id %d tag %d\n", fcall->size, fcall->id,
-                fcall->tag);
-
-        /* now encode it */
-        switch (fcall->id) {
-        default:
-                eprintk(KERN_ERR, "bad msg type: %d\n", fcall->id);
-                return -EPROTO;
-        case TVERSION:
-                buf_put_int32(bufp, fcall->params.tversion.msize);
-                buf_put_string(bufp, fcall->params.tversion.version);
-                break;
-        case TAUTH:
-                buf_put_int32(bufp, fcall->params.tauth.afid);
-                buf_put_string(bufp, fcall->params.tauth.uname);
-                buf_put_string(bufp, fcall->params.tauth.aname);
-                break;
-        case TFLUSH:
-                buf_put_int16(bufp, fcall->params.tflush.oldtag);
-                break;
-        case TATTACH:
-                buf_put_int32(bufp, fcall->params.tattach.fid);
-                buf_put_int32(bufp, fcall->params.tattach.afid);
-                buf_put_string(bufp, fcall->params.tattach.uname);
-                buf_put_string(bufp, fcall->params.tattach.aname);
-                break;
-        case TWALK:
-                buf_put_int32(bufp, fcall->params.twalk.fid);
-                buf_put_int32(bufp, fcall->params.twalk.newfid);
-                buf_put_int16(bufp, fcall->params.twalk.nwname);
-                for (i = 0; i < fcall->params.twalk.nwname; i++)
-                        buf_put_string(bufp, fcall->params.twalk.wnames[i]);
-                break;
-        case TOPEN:
-                buf_put_int32(bufp, fcall->params.topen.fid);
-                buf_put_int8(bufp, fcall->params.topen.mode);
-                break;
-        case TCREATE:
-                buf_put_int32(bufp, fcall->params.tcreate.fid);
-                buf_put_string(bufp, fcall->params.tcreate.name);
-                buf_put_int32(bufp, fcall->params.tcreate.perm);
-                buf_put_int8(bufp, fcall->params.tcreate.mode);
-                break;
-        case TREAD:
-                buf_put_int32(bufp, fcall->params.tread.fid);
-                buf_put_int64(bufp, fcall->params.tread.offset);
-                buf_put_int32(bufp, fcall->params.tread.count);
-                break;
-        case TWRITE:
-                buf_put_int32(bufp, fcall->params.twrite.fid);
-                buf_put_int64(bufp, fcall->params.twrite.offset);
-                buf_put_int32(bufp, fcall->params.twrite.count);
-                buf_put_data(bufp, fcall->params.twrite.data,
-                             fcall->params.twrite.count);
-                break;
-        case TCLUNK:
-                buf_put_int32(bufp, fcall->params.tclunk.fid);
-                break;
-        case TREMOVE:
-                buf_put_int32(bufp, fcall->params.tremove.fid);
-                break;
-        case TSTAT:
-                buf_put_int32(bufp, fcall->params.tstat.fid);
-                break;
-        case TWSTAT:
-                buf_put_int32(bufp, fcall->params.twstat.fid);
-                stat = fcall->params.twstat.stat;
-
-                buf_put_int16(bufp, stat->size + 2);
-                serialize_stat(stat, bufp, extended);
-                break;
-        }
-
-        if (buf_check_overflow(bufp)) {
-                dprintk(DEBUG_ERROR, "buffer overflow\n");
-                return -EIO;
-        }
-
-        return fcall->size;
+        else
+                return bufp->p - p;
 }
 
 /**
@@ -611,18 +348,14 @@ v9fs_serialize_fcall(struct v9fs_fcall *fcall, void *data, u32 datalen,
 
 int
 v9fs_deserialize_fcall(void *buf, u32 buflen, struct v9fs_fcall *rcall,
-                       int rcalllen, int extended)
+                       int extended)
 {
 
         struct cbuf buffer;
         struct cbuf *bufp = &buffer;
-        struct cbuf dbuffer;
-        struct cbuf *dbufp = &dbuffer;
         int i = 0;
 
         buf_init(bufp, buf, buflen);
-        buf_init(dbufp, (char *)rcall + sizeof(struct v9fs_fcall),
-                 rcalllen - sizeof(struct v9fs_fcall));
 
         rcall->size = buf_get_int32(bufp);
         rcall->id = buf_get_int8(bufp);
@@ -630,13 +363,14 @@ v9fs_deserialize_fcall(void *buf, u32 buflen, struct v9fs_fcall *rcall,
 
         dprintk(DEBUG_CONV, "size %d id %d tag %d\n", rcall->size, rcall->id,
                 rcall->tag);
+
         switch (rcall->id) {
         default:
                 eprintk(KERN_ERR, "unknown message type: %d\n", rcall->id);
                 return -EPROTO;
         case RVERSION:
                 rcall->params.rversion.msize = buf_get_int32(bufp);
-                rcall->params.rversion.version = buf_get_stringb(bufp, dbufp);
+                buf_get_str(bufp, &rcall->params.rversion.version);
                 break;
         case RFLUSH:
                 break;
@@ -647,40 +381,27 @@ v9fs_deserialize_fcall(void *buf, u32 buflen, struct v9fs_fcall *rcall,
                 break;
         case RWALK:
                 rcall->params.rwalk.nwqid = buf_get_int16(bufp);
-                if (rcall->params.rwalk.nwqid > 16) {
-                        eprintk(KERN_ERR, "Rwalk with more than 16 qids: %d\n",
-                                rcall->params.rwalk.nwqid);
+                if (rcall->params.rwalk.nwqid > V9FS_MAXWELEM) {
+                        eprintk(KERN_ERR, "Rwalk with more than %d qids: %d\n",
+                                V9FS_MAXWELEM, rcall->params.rwalk.nwqid);
                         return -EPROTO;
                 }
 
-                rcall->params.rwalk.wqids = buf_alloc(dbufp,
-                      rcall->params.rwalk.nwqid * sizeof(struct v9fs_qid));
-                if (rcall->params.rwalk.wqids)
-                        for (i = 0; i < rcall->params.rwalk.nwqid; i++) {
-                                rcall->params.rwalk.wqids[i].type =
-                                    buf_get_int8(bufp);
-                                rcall->params.rwalk.wqids[i].version =
-                                    buf_get_int16(bufp);
-                                rcall->params.rwalk.wqids[i].path =
-                                    buf_get_int64(bufp);
-                        }
+                for (i = 0; i < rcall->params.rwalk.nwqid; i++)
+                        buf_get_qid(bufp, &rcall->params.rwalk.wqids[i]);
                 break;
         case ROPEN:
-                rcall->params.ropen.qid.type = buf_get_int8(bufp);
-                rcall->params.ropen.qid.version = buf_get_int32(bufp);
-                rcall->params.ropen.qid.path = buf_get_int64(bufp);
+                buf_get_qid(bufp, &rcall->params.ropen.qid);
                 rcall->params.ropen.iounit = buf_get_int32(bufp);
                 break;
         case RCREATE:
-                rcall->params.rcreate.qid.type = buf_get_int8(bufp);
-                rcall->params.rcreate.qid.version = buf_get_int32(bufp);
-                rcall->params.rcreate.qid.path = buf_get_int64(bufp);
+                buf_get_qid(bufp, &rcall->params.rcreate.qid);
                 rcall->params.rcreate.iounit = buf_get_int32(bufp);
                 break;
         case RREAD:
                 rcall->params.rread.count = buf_get_int32(bufp);
-                rcall->params.rread.data = buf_get_datab(bufp, dbufp,
-                        rcall->params.rread.count);
+                rcall->params.rread.data = bufp->p;
+                buf_check_size(bufp, rcall->params.rread.count);
                 break;
         case RWRITE:
                 rcall->params.rwrite.count = buf_get_int32(bufp);
@@ -691,22 +412,442 @@ v9fs_deserialize_fcall(void *buf, u32 buflen, struct v9fs_fcall *rcall,
                 break;
         case RSTAT:
                 buf_get_int16(bufp);
-                rcall->params.rstat.stat =
-                    deserialize_statb(bufp, dbufp, extended);
+                buf_get_stat(bufp, &rcall->params.rstat.stat, extended);
                 break;
         case RWSTAT:
                 break;
         case RERROR:
-                rcall->params.rerror.error = buf_get_stringb(bufp, dbufp);
+                buf_get_str(bufp, &rcall->params.rerror.error);
                 if (extended)
                         rcall->params.rerror.errno = buf_get_int16(bufp);
                 break;
         }
 
-        if (buf_check_overflow(bufp) || buf_check_overflow(dbufp)) {
+        if (buf_check_overflow(bufp)) {
                 dprintk(DEBUG_ERROR, "buffer overflow\n");
                 return -EIO;
         }
 
-        return rcall->size;
+        return bufp->p - bufp->sp;
+}
+
+static inline void v9fs_put_int8(struct cbuf *bufp, u8 val, u8 * p)
+{
+        *p = val;
+        buf_put_int8(bufp, val);
+}
+
+static inline void v9fs_put_int16(struct cbuf *bufp, u16 val, u16 * p)
+{
+        *p = val;
+        buf_put_int16(bufp, val);
+}
+
+static inline void v9fs_put_int32(struct cbuf *bufp, u32 val, u32 * p)
+{
+        *p = val;
+        buf_put_int32(bufp, val);
+}
+
+static inline void v9fs_put_int64(struct cbuf *bufp, u64 val, u64 * p)
+{
+        *p = val;
+        buf_put_int64(bufp, val);
+}
+
+static inline void
+v9fs_put_str(struct cbuf *bufp, char *data, struct v9fs_str *str)
+{
+        if (data) {
+                str->len = strlen(data);
+                str->str = bufp->p;
+        } else {
+                str->len = 0;
+                str->str = NULL;
+        }
+
+        buf_put_stringn(bufp, data, str->len);
+}
+
+static inline int
+v9fs_put_user_data(struct cbuf *bufp, const char __user * data, int count,
+                   unsigned char **pdata)
+{
+        *pdata = buf_alloc(bufp, count);
+        return copy_from_user(*pdata, data, count);
+}
+
+static void
+v9fs_put_wstat(struct cbuf *bufp, struct v9fs_wstat *wstat,
+               struct v9fs_stat *stat, int statsz, int extended)
+{
+        v9fs_put_int16(bufp, statsz, &stat->size);
+        v9fs_put_int16(bufp, wstat->type, &stat->type);
+        v9fs_put_int32(bufp, wstat->dev, &stat->dev);
+        v9fs_put_int8(bufp, wstat->qid.type, &stat->qid.type);
+        v9fs_put_int32(bufp, wstat->qid.version, &stat->qid.version);
+        v9fs_put_int64(bufp, wstat->qid.path, &stat->qid.path);
+        v9fs_put_int32(bufp, wstat->mode, &stat->mode);
+        v9fs_put_int32(bufp, wstat->atime, &stat->atime);
+        v9fs_put_int32(bufp, wstat->mtime, &stat->mtime);
+        v9fs_put_int64(bufp, wstat->length, &stat->length);
+
+        v9fs_put_str(bufp, wstat->name, &stat->name);
+        v9fs_put_str(bufp, wstat->uid, &stat->uid);
+        v9fs_put_str(bufp, wstat->gid, &stat->gid);
+        v9fs_put_str(bufp, wstat->muid, &stat->muid);
+
+        if (extended) {
+                v9fs_put_str(bufp, wstat->extension, &stat->extension);
+                v9fs_put_int32(bufp, wstat->n_uid, &stat->n_uid);
+                v9fs_put_int32(bufp, wstat->n_gid, &stat->n_gid);
+                v9fs_put_int32(bufp, wstat->n_muid, &stat->n_muid);
+        }
+}
+
+static struct v9fs_fcall *
+v9fs_create_common(struct cbuf *bufp, u32 size, u8 id)
+{
+        struct v9fs_fcall *fc;
+
+        size += 4 + 1 + 2;      /* size[4] id[1] tag[2] */
+        fc = kmalloc(sizeof(struct v9fs_fcall) + size, GFP_KERNEL);
+        if (!fc)
+                return ERR_PTR(-ENOMEM);
+
+        fc->sdata = (char *)fc + sizeof(*fc);
+
+        buf_init(bufp, (char *)fc->sdata, size);
+        v9fs_put_int32(bufp, size, &fc->size);
+        v9fs_put_int8(bufp, id, &fc->id);
+        v9fs_put_int16(bufp, V9FS_NOTAG, &fc->tag);
+
+        return fc;
+}
+
+void v9fs_set_tag(struct v9fs_fcall *fc, u16 tag)
+{
+        *(__le16 *) (fc->sdata + 5) = cpu_to_le16(tag);
+}
+
+struct v9fs_fcall *v9fs_create_tversion(u32 msize, char *version)
+{
+        int size;
+        struct v9fs_fcall *fc;
+        struct cbuf buffer;
+        struct cbuf *bufp = &buffer;
+
+        size = 4 + 2 + strlen(version); /* msize[4] version[s] */
+        fc = v9fs_create_common(bufp, size, TVERSION);
+        if (IS_ERR(fc))
+                goto error;
+
+        v9fs_put_int32(bufp, msize, &fc->params.tversion.msize);
+        v9fs_put_str(bufp, version, &fc->params.tversion.version);
+
+        if (buf_check_overflow(bufp)) {
+                kfree(fc);
+                fc = ERR_PTR(-ENOMEM);
+        }
+      error:
+        return fc;
+}
+
+struct v9fs_fcall *v9fs_create_tauth(u32 afid, char *uname, char *aname)
+{
+        int size;
+        struct v9fs_fcall *fc;
+        struct cbuf buffer;
+        struct cbuf *bufp = &buffer;
+
+        size = 4 + 2 + strlen(uname) + 2 + strlen(aname);       /* afid[4] uname[s] aname[s] */
+        fc = v9fs_create_common(bufp, size, TAUTH);
+        if (IS_ERR(fc))
+                goto error;
+
+        v9fs_put_int32(bufp, afid, &fc->params.tauth.afid);
+        v9fs_put_str(bufp, uname, &fc->params.tauth.uname);
+        v9fs_put_str(bufp, aname, &fc->params.tauth.aname);
+
+        if (buf_check_overflow(bufp)) {
+                kfree(fc);
+                fc = ERR_PTR(-ENOMEM);
+        }
+      error:
+        return fc;
+}
+
+struct v9fs_fcall *
+v9fs_create_tattach(u32 fid, u32 afid, char *uname, char *aname)
+{
+        int size;
+        struct v9fs_fcall *fc;
+        struct cbuf buffer;
+        struct cbuf *bufp = &buffer;
+
+        size = 4 + 4 + 2 + strlen(uname) + 2 + strlen(aname);   /* fid[4] afid[4] uname[s] aname[s] */
+        fc = v9fs_create_common(bufp, size, TATTACH);
+        if (IS_ERR(fc))
+                goto error;
+
+        v9fs_put_int32(bufp, fid, &fc->params.tattach.fid);
+        v9fs_put_int32(bufp, afid, &fc->params.tattach.afid);
+        v9fs_put_str(bufp, uname, &fc->params.tattach.uname);
+        v9fs_put_str(bufp, aname, &fc->params.tattach.aname);
+
+      error:
+        return fc;
+}
+
+struct v9fs_fcall *v9fs_create_tflush(u16 oldtag)
+{
+        int size;
+        struct v9fs_fcall *fc;
+        struct cbuf buffer;
+        struct cbuf *bufp = &buffer;
+
+        size = 2;               /* oldtag[2] */
+        fc = v9fs_create_common(bufp, size, TFLUSH);
+        if (IS_ERR(fc))
+                goto error;
+
+        v9fs_put_int16(bufp, oldtag, &fc->params.tflush.oldtag);
+
+        if (buf_check_overflow(bufp)) {
+                kfree(fc);
+                fc = ERR_PTR(-ENOMEM);
+        }
+      error:
+        return fc;
+}
+
+struct v9fs_fcall *v9fs_create_twalk(u32 fid, u32 newfid, u16 nwname,
+                                     char **wnames)
+{
+        int i, size;
+        struct v9fs_fcall *fc;
+        struct cbuf buffer;
+        struct cbuf *bufp = &buffer;
+
+        if (nwname > V9FS_MAXWELEM) {
+                dprintk(DEBUG_ERROR, "nwname > %d\n", V9FS_MAXWELEM);
+                return NULL;
+        }
+
+        size = 4 + 4 + 2;       /* fid[4] newfid[4] nwname[2] ... */
+        for (i = 0; i < nwname; i++) {
+                size += 2 + strlen(wnames[i]);  /* wname[s] */
+        }
+
+        fc = v9fs_create_common(bufp, size, TWALK);
+        if (IS_ERR(fc))
+                goto error;
+
+        v9fs_put_int32(bufp, fid, &fc->params.twalk.fid);
+        v9fs_put_int32(bufp, newfid, &fc->params.twalk.newfid);
+        v9fs_put_int16(bufp, nwname, &fc->params.twalk.nwname);
+        for (i = 0; i < nwname; i++) {
+                v9fs_put_str(bufp, wnames[i], &fc->params.twalk.wnames[i]);
+        }
+
+        if (buf_check_overflow(bufp)) {
+                kfree(fc);
+                fc = ERR_PTR(-ENOMEM);
+        }
+      error:
+        return fc;
+}
+
+struct v9fs_fcall *v9fs_create_topen(u32 fid, u8 mode)
+{
+        int size;
+        struct v9fs_fcall *fc;
+        struct cbuf buffer;
+        struct cbuf *bufp = &buffer;
+
+        size = 4 + 1;           /* fid[4] mode[1] */
+        fc = v9fs_create_common(bufp, size, TOPEN);
+        if (IS_ERR(fc))
+                goto error;
+
+        v9fs_put_int32(bufp, fid, &fc->params.topen.fid);
+        v9fs_put_int8(bufp, mode, &fc->params.topen.mode);
+
+        if (buf_check_overflow(bufp)) {
+                kfree(fc);
+                fc = ERR_PTR(-ENOMEM);
+        }
+      error:
+        return fc;
+}
+
+struct v9fs_fcall *v9fs_create_tcreate(u32 fid, char *name, u32 perm, u8 mode)
+{
+        int size;
+        struct v9fs_fcall *fc;
+        struct cbuf buffer;
+        struct cbuf *bufp = &buffer;
+
+        size = 4 + 2 + strlen(name) + 4 + 1;    /* fid[4] name[s] perm[4] mode[1] */
+        fc = v9fs_create_common(bufp, size, TCREATE);
+        if (IS_ERR(fc))
+                goto error;
+
+        v9fs_put_int32(bufp, fid, &fc->params.tcreate.fid);
+        v9fs_put_str(bufp, name, &fc->params.tcreate.name);
+        v9fs_put_int32(bufp, perm, &fc->params.tcreate.perm);
+        v9fs_put_int8(bufp, mode, &fc->params.tcreate.mode);
+
+        if (buf_check_overflow(bufp)) {
+                kfree(fc);
+                fc = ERR_PTR(-ENOMEM);
+        }
+      error:
+        return fc;
+}
+
+struct v9fs_fcall *v9fs_create_tread(u32 fid, u64 offset, u32 count)
+{
+        int size;
+        struct v9fs_fcall *fc;
+        struct cbuf buffer;
+        struct cbuf *bufp = &buffer;
+
+        size = 4 + 8 + 4;       /* fid[4] offset[8] count[4] */
+        fc = v9fs_create_common(bufp, size, TREAD);
+        if (IS_ERR(fc))
+                goto error;
+
+        v9fs_put_int32(bufp, fid, &fc->params.tread.fid);
+        v9fs_put_int64(bufp, offset, &fc->params.tread.offset);
+        v9fs_put_int32(bufp, count, &fc->params.tread.count);
+
+        if (buf_check_overflow(bufp)) {
+                kfree(fc);
+                fc = ERR_PTR(-ENOMEM);
+        }
+      error:
+        return fc;
+}
+
+struct v9fs_fcall *v9fs_create_twrite(u32 fid, u64 offset, u32 count,
+                                      const char __user * data)
+{
+        int size, err;
+        struct v9fs_fcall *fc;
+        struct cbuf buffer;
+        struct cbuf *bufp = &buffer;
+
+        size = 4 + 8 + 4 + count;       /* fid[4] offset[8] count[4] data[count] */
+        fc = v9fs_create_common(bufp, size, TWRITE);
+        if (IS_ERR(fc))
+                goto error;
+
+        v9fs_put_int32(bufp, fid, &fc->params.twrite.fid);
+        v9fs_put_int64(bufp, offset, &fc->params.twrite.offset);
+        v9fs_put_int32(bufp, count, &fc->params.twrite.count);
+        err = v9fs_put_user_data(bufp, data, count, &fc->params.twrite.data);
+        if (err) {
+                kfree(fc);
+                fc = ERR_PTR(err);
+        }
+
+        if (buf_check_overflow(bufp)) {
+                kfree(fc);
+                fc = ERR_PTR(-ENOMEM);
+        }
+      error:
+        return fc;
+}
+
+struct v9fs_fcall *v9fs_create_tclunk(u32 fid)
+{
+        int size;
+        struct v9fs_fcall *fc;
+        struct cbuf buffer;
+        struct cbuf *bufp = &buffer;
+
+        size = 4;               /* fid[4] */
+        fc = v9fs_create_common(bufp, size, TCLUNK);
+        if (IS_ERR(fc))
+                goto error;
+
+        v9fs_put_int32(bufp, fid, &fc->params.tclunk.fid);
+
+        if (buf_check_overflow(bufp)) {
+                kfree(fc);
+                fc = ERR_PTR(-ENOMEM);
+        }
+      error:
+        return fc;
+}
+
+struct v9fs_fcall *v9fs_create_tremove(u32 fid)
+{
+        int size;
+        struct v9fs_fcall *fc;
+        struct cbuf buffer;
+        struct cbuf *bufp = &buffer;
+
+        size = 4;               /* fid[4] */
+        fc = v9fs_create_common(bufp, size, TREMOVE);
+        if (IS_ERR(fc))
+                goto error;
+
+        v9fs_put_int32(bufp, fid, &fc->params.tremove.fid);
+
+        if (buf_check_overflow(bufp)) {
+                kfree(fc);
+                fc = ERR_PTR(-ENOMEM);
+        }
+      error:
+        return fc;
+}
+
+struct v9fs_fcall *v9fs_create_tstat(u32 fid)
+{
+        int size;
+        struct v9fs_fcall *fc;
+        struct cbuf buffer;
+        struct cbuf *bufp = &buffer;
+
+        size = 4;               /* fid[4] */
+        fc = v9fs_create_common(bufp, size, TSTAT);
+        if (IS_ERR(fc))
+                goto error;
+
+        v9fs_put_int32(bufp, fid, &fc->params.tstat.fid);
+
+        if (buf_check_overflow(bufp)) {
+                kfree(fc);
+                fc = ERR_PTR(-ENOMEM);
+        }
+      error:
+        return fc;
+}
+
+struct v9fs_fcall *v9fs_create_twstat(u32 fid, struct v9fs_wstat *wstat,
+                                      int extended)
+{
+        int size, statsz;
+        struct v9fs_fcall *fc;
+        struct cbuf buffer;
+        struct cbuf *bufp = &buffer;
+
+        statsz = v9fs_size_wstat(wstat, extended);
+        size = 4 + 2 + 2 + statsz;      /* fid[4] stat[n] */
+        fc = v9fs_create_common(bufp, size, TWSTAT);
+        if (IS_ERR(fc))
+                goto error;
+
+        v9fs_put_int32(bufp, fid, &fc->params.twstat.fid);
+        buf_put_int16(bufp, statsz + 2);
+        v9fs_put_wstat(bufp, wstat, &fc->params.twstat.stat, statsz, extended);
+
+        if (buf_check_overflow(bufp)) {
+                kfree(fc);
+                fc = ERR_PTR(-ENOMEM);
+        }
+      error:
+        return fc;
 }