[Qemu-devel] qemu:virtio-9p: [RFC] [PATCH 01/02] Send iounit to client for read/write operations

[M. Mohan Kumar]

Compute iounit based on the host filesystem block size and pass it to
client with open/create response. Also return iounit as statfs's f_bsize
for optimal block size transfers.

Signed-off-by: M. Mohan Kumar <mo...@in.ibm.com>
---
 hw/virtio-9p.c |   56 ++++++++++++++++++++++++++++++++++++++++++--------------
 hw/virtio-9p.h |    3 +++
 2 files changed, 45 insertions(+), 14 deletions(-)

diff --git a/hw/virtio-9p.c b/hw/virtio-9p.c
index f087122..4357f1f 100644
--- a/hw/virtio-9p.c
+++ b/hw/virtio-9p.c
@@ -1,4 +1,4 @@
-/*
+               /*
  * Virtio 9p backend
  *
  * Copyright IBM, Corp. 2010
@@ -269,6 +269,11 @@ static int v9fs_do_fsync(V9fsState *s, int fd)
     return s->ops->fsync(&s->ctx, fd);
 }
 
+static int v9fs_do_statfs(V9fsState *s, V9fsString *path, struct statfs *stbuf)
+{
+    return s->ops->statfs(&s->ctx, path->data, stbuf);
+}
+
 static void v9fs_string_init(V9fsString *str)
 {
     str->data = NULL;
@@ -1035,11 +1040,10 @@ static void v9fs_fix_path(V9fsString *dst, V9fsString 
*src, int len)
 
 static void v9fs_version(V9fsState *s, V9fsPDU *pdu)
 {
-    int32_t msize;
     V9fsString version;
     size_t offset = 7;
 
-    pdu_unmarshal(pdu, offset, "ds", &msize, &version);
+    pdu_unmarshal(pdu, offset, "ds", &s->msize, &version);
 
     if (!strcmp(version.data, "9P2000.u")) {
         s->proto_version = V9FS_PROTO_2000U;
@@ -1049,7 +1053,7 @@ static void v9fs_version(V9fsState *s, V9fsPDU *pdu)
         v9fs_string_sprintf(&version, "unknown");
     }
 
-    offset += pdu_marshal(pdu, offset, "ds", msize, &version);
+    offset += pdu_marshal(pdu, offset, "ds", s->msize, &version);
     complete_pdu(s, pdu, offset);
 
     v9fs_string_free(&version);
@@ -1304,6 +1308,20 @@ out:
     v9fs_walk_complete(s, vs, err);
 }
 
+static int32_t get_iounit(V9fsState *s, V9fsString *name)
+{
+    struct statfs stbuf;
+    int32_t iounit = 0;
+
+
+    if (!v9fs_do_statfs(s, name, &stbuf)) {
+        iounit = stbuf.f_bsize;
+        iounit *= (s->msize - P9_IOHDRSZ)/stbuf.f_bsize;
+    }
+
+    return iounit;
+}
+
 static void v9fs_open_post_opendir(V9fsState *s, V9fsOpenState *vs, int err)
 {
     if (vs->fidp->dir == NULL) {
@@ -1321,12 +1339,15 @@ out:
 
 static void v9fs_open_post_open(V9fsState *s, V9fsOpenState *vs, int err)
 {
+    int32_t iounit;
+
     if (vs->fidp->fd == -1) {
         err = -errno;
         goto out;
     }
 
-    vs->offset += pdu_marshal(vs->pdu, vs->offset, "Qd", &vs->qid, 0);
+    iounit = get_iounit(s, &vs->fidp->path);
+    vs->offset += pdu_marshal(vs->pdu, vs->offset, "Qd", &vs->qid, iounit);
     err = vs->offset;
 out:
     complete_pdu(s, vs->pdu, err);
@@ -1800,11 +1821,16 @@ out:
 
 static void v9fs_post_create(V9fsState *s, V9fsCreateState *vs, int err)
 {
+    int32_t iounit;
+
+    iounit = get_iounit(s, &vs->fidp->path);
+
     if (err == 0) {
         v9fs_string_copy(&vs->fidp->path, &vs->fullname);
         stat_to_qid(&vs->stbuf, &vs->qid);
 
-        vs->offset += pdu_marshal(vs->pdu, vs->offset, "Qd", &vs->qid, 0);
+        vs->offset += pdu_marshal(vs->pdu, vs->offset, "Qd", &vs->qid,
+                iounit);
 
         err = vs->offset;
     }
@@ -2295,23 +2321,25 @@ out:
     qemu_free(vs);
 }
 
-static int v9fs_do_statfs(V9fsState *s, V9fsString *path, struct statfs *stbuf)
-{
-    return s->ops->statfs(&s->ctx, path->data, stbuf);
-}
-
 static void v9fs_statfs_post_statfs(V9fsState *s, V9fsStatfsState *vs, int err)
 {
+    int32_t bsize_factor;
+
     if (err) {
         err = -errno;
         goto out;
     }
 
+    bsize_factor = (s->msize - P9_IOHDRSZ)/vs->stbuf.f_bsize;
+    if (!bsize_factor) {
+        bsize_factor = 1;
+    }
     vs->v9statfs.f_type = vs->stbuf.f_type;
     vs->v9statfs.f_bsize = vs->stbuf.f_bsize;
-    vs->v9statfs.f_blocks = vs->stbuf.f_blocks;
-    vs->v9statfs.f_bfree = vs->stbuf.f_bfree;
-    vs->v9statfs.f_bavail = vs->stbuf.f_bavail;
+    vs->v9statfs.f_bsize *= bsize_factor;
+    vs->v9statfs.f_blocks = vs->stbuf.f_blocks/bsize_factor;
+    vs->v9statfs.f_bfree = vs->stbuf.f_bfree/bsize_factor;
+    vs->v9statfs.f_bavail = vs->stbuf.f_bavail/bsize_factor;
     vs->v9statfs.f_files = vs->stbuf.f_files;
     vs->v9statfs.f_ffree = vs->stbuf.f_ffree;
     vs->v9statfs.fsid_val = (unsigned int) vs->stbuf.f_fsid.__val[0] |
diff --git a/hw/virtio-9p.h b/hw/virtio-9p.h
index 6b3d4a4..9264163 100644
--- a/hw/virtio-9p.h
+++ b/hw/virtio-9p.h
@@ -72,6 +72,8 @@ enum p9_proto_version {
 #define P9_NOFID    (u32)(~0)
 #define P9_MAXWELEM 16
 
+#define P9_IOHDRSZ 24
+
 typedef struct V9fsPDU V9fsPDU;
 
 struct V9fsPDU
@@ -156,6 +158,7 @@ typedef struct V9fsState
     uint8_t *tag;
     size_t config_size;
     enum p9_proto_version proto_version;
+    int32_t msize;
 } V9fsState;
 
 typedef struct V9fsCreateState {
-- 
1.6.6.1