[Qemu-devel] [PATCH 05/20] virtio-9p: Compute iounit based on host filesystem block size

["Venkateswararao Jujjuri (JV)" <jvrao@linux.vnet.ibm.com>]

From: M. Mohan Kumar <mohan@in.ibm.com>

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 <mohan@in.ibm.com>
Reviewd-by: Sripathi Kodi <sripathik@in.ibm.com>
Signed-off-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
---
 hw/virtio-9p.c |   96 +++++++++++++++++++++++++++++++++++++++++++++-----------
 hw/virtio-9p.h |    9 +++++
 2 files changed, 86 insertions(+), 19 deletions(-)

diff --git a/hw/virtio-9p.c b/hw/virtio-9p.c
index 2918194..00527c4 100644
--- a/hw/virtio-9p.c
+++ b/hw/virtio-9p.c
@@ -253,6 +253,11 @@ 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;
@@ -1019,11 +1024,10 @@ 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;
@@ -1033,7 +1037,7 @@ 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);
@@ -1288,6 +1292,26 @@ out:
     v9fs_walk_complete(s, vs, err);
 }
 
+static int32_t get_iounit(V9fsState *s, V9fsString *name)
+{
+    struct statfs stbuf;
+    int32_t iounit = 0;
+
+    /*
+     * iounit should be multiples of f_bsize (host filesystem block size
+     * and as well as less than (client msize - P9_IOHDRSZ))
+     */
+    if (!v9fs_do_statfs(s, name, &stbuf)) {
+        iounit = stbuf.f_bsize;
+        iounit *= (s->msize - P9_IOHDRSZ)/stbuf.f_bsize;
+    }
+
+    if (!iounit) {
+        iounit = s->msize - P9_IOHDRSZ;
+    }
+    return iounit;
+}
+
 static void v9fs_open_post_opendir(V9fsState *s, V9fsOpenState *vs, int err)
 {
     if (vs->fidp->dir == NULL) {
@@ -1303,6 +1327,15 @@ out:
 
 }
 
+static void v9fs_open_post_getiounit(V9fsState *s, V9fsOpenState *vs)
+{
+    int err;
+    vs->offset += pdu_marshal(vs->pdu, vs->offset, "Qd", &vs->qid, vs->iounit);
+    err = vs->offset;
+    complete_pdu(s, vs->pdu, err);
+    qemu_free(vs);
+}
+
 static void v9fs_open_post_open(V9fsState *s, V9fsOpenState *vs, int err)
 {
     if (vs->fidp->fd == -1) {
@@ -1310,8 +1343,9 @@ static void v9fs_open_post_open(V9fsState *s, V9fsOpenState *vs, int err)
         goto out;
     }
 
-    vs->offset += pdu_marshal(vs->pdu, vs->offset, "Qd", &vs->qid, 0);
-    err = vs->offset;
+    vs->iounit = get_iounit(s, &vs->fidp->path);
+    v9fs_open_post_getiounit(s, vs);
+    return;
 out:
     complete_pdu(s, vs->pdu, err);
     qemu_free(vs);
@@ -1794,15 +1828,28 @@ out:
     qemu_free(vs);
 }
 
-static void v9fs_post_create(V9fsState *s, V9fsCreateState *vs, int err)
+static void v9fs_create_post_getiounit(V9fsState *s, V9fsCreateState *vs)
 {
-    if (err == 0) {
-        v9fs_string_copy(&vs->fidp->path, &vs->fullname);
-        stat_to_qid(&vs->stbuf, &vs->qid);
+    int err;
+    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, vs->iounit);
+    err = vs->offset;
 
-        err = vs->offset;
+    complete_pdu(s, vs->pdu, err);
+    v9fs_string_free(&vs->name);
+    v9fs_string_free(&vs->extension);
+    v9fs_string_free(&vs->fullname);
+    qemu_free(vs);
+}
+
+static void v9fs_post_create(V9fsState *s, V9fsCreateState *vs, int err)
+{
+    if (err == 0) {
+        vs->iounit = get_iounit(s, &vs->fidp->path);
+        v9fs_create_post_getiounit(s, vs);
+        return;
     }
 
     complete_pdu(s, vs->pdu, err);
@@ -2267,23 +2314,34 @@ 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;
     }
 
+    /*
+     * compute bsize factor based on host file system block size
+     * and client msize
+     */
+    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;
+    /*
+     * f_bsize is adjusted(multiplied) by bsize factor, so we need to
+     * adjust(divide) the number of blocks, free blocks and available
+     * blocks by 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 9773659..4ee3830 100644
--- a/hw/virtio-9p.h
+++ b/hw/virtio-9p.h
@@ -70,6 +70,12 @@ enum p9_proto_version {
 #define P9_NOFID    (u32)(~0)
 #define P9_MAXWELEM 16
 
+/*
+ * ample room for Twrite/Rread header
+ * size[4] Tread/Twrite tag[2] fid[4] offset[8] count[4]
+ */
+#define P9_IOHDRSZ 24
+
 typedef struct V9fsPDU V9fsPDU;
 
 struct V9fsPDU
@@ -154,6 +160,7 @@ typedef struct V9fsState
     uint8_t *tag;
     size_t config_size;
     enum p9_proto_version proto_version;
+    int32_t msize;
 } V9fsState;
 
 typedef struct V9fsCreateState {
@@ -167,6 +174,7 @@ typedef struct V9fsCreateState {
     V9fsString name;
     V9fsString extension;
     V9fsString fullname;
+    int iounit;
 } V9fsCreateState;
 
 typedef struct V9fsStatState {
@@ -197,6 +205,7 @@ typedef struct V9fsOpenState {
     V9fsFidState *fidp;
     V9fsQID qid;
     struct stat stbuf;
+    int iounit;
 } V9fsOpenState;
 
 typedef struct V9fsReadState {
-- 
1.6.5.2