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

login
register
mail settings
Submitter Mohan Kumar M
Date June 1, 2010, 2:17 p.m.
Message ID <1275401834-27520-1-git-send-email-mohan@in.ibm.com>
Download mbox | patch
Permalink /patch/54210/
State New
Headers show

Comments

Mohan Kumar M - June 1, 2010, 2:17 p.m.
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>
---
 hw/virtio-9p.c |   56 ++++++++++++++++++++++++++++++++++++++++++--------------
 hw/virtio-9p.h |    3 +++
 2 files changed, 45 insertions(+), 14 deletions(-)
Aneesh Kumar K.V - June 2, 2010, 11:47 a.m.
On Tue,  1 Jun 2010 19:47:14 +0530, "M. Mohan Kumar" <mohan@in.ibm.com> wrote:
> 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>
> ---
>  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 @@
> -/*
> +		/*


why ?

>   * 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;
> +    }
> +


Add a comment here explaining why we do the above math.


> +    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);


We may later want to track this per exported mount point and to
get_iounit only once per exported mount point.

>      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;


Add a comment around whey we are doing this. 


>      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

Add a comment how size 24 is arrived. 

> +
>  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 {
> -- 

-aneesh
Sripathi Kodi - June 4, 2010, 6:51 a.m.
On Tue,  1 Jun 2010 19:47:14 +0530
"M. Mohan Kumar" <mohan@in.ibm.com> wrote:

> 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>
> ---
>  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;

If (s->msize - P9_IOHDRSZ) is less than stbuf.f_bsize iounit becomes
zero. See below.

> +    }
> +
> +    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;
> +    }

Again, if (s->msize - P9_IOHDRSZ) is less than stbuf.f_bsize
bsize_factor becomes zero. The following divisions become divide by
zero!

Thanks,
Sripathi.

>      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
> 
>
jvrao - June 6, 2010, 7:48 p.m.
Sripathi Kodi wrote:
> On Tue,  1 Jun 2010 19:47:14 +0530
> "M. Mohan Kumar" <mohan@in.ibm.com> wrote:
> 
>> 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>
>> ---
>>  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;
> 
> If (s->msize - P9_IOHDRSZ) is less than stbuf.f_bsize iounit becomes
> zero. See below.
> 
>> +    }
>> +
>> +    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;
>> +    }
> 
> Again, if (s->msize - P9_IOHDRSZ) is less than stbuf.f_bsize
> bsize_factor becomes zero. The following divisions become divide by
> zero!

Yes, I think we should leave iounit alone return it with open/create and handle it
as per the 9P protocol..and return whatever the fileserver gives for stat and satatfs.

- JV

> 
> Thanks,
> Sripathi.
> 
>>      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
>>
>>
>

Patch

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 {