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

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

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
>>
>>
>