Re: [Qemu-devel] 9p: [RFC] [PATCH 02/02] Make use of iounit for read/write

[Sripathi Kodi]

On Tue,  1 Jun 2010 19:47:49 +0530
"M. Mohan Kumar" <address@hidden> wrote:

> Change the v9fs_file_readn function to limit the maximum transfer size
> based on the iounit instead of msize.
> 
> Also remove the redundant check for limiting the transfer size in
> v9fs_file_write. This check is done by p9_client_write.
> 
> Signed-off-by: M. Mohan Kumar <address@hidden>
> ---
>  fs/9p/vfs_file.c |   10 ++--------
>  1 files changed, 2 insertions(+), 8 deletions(-)
> 
> diff --git a/fs/9p/vfs_file.c b/fs/9p/vfs_file.c
> index 25b300e..b8c0891 100644
> --- a/fs/9p/vfs_file.c
> +++ b/fs/9p/vfs_file.c
> @@ -160,7 +160,7 @@ v9fs_file_readn(struct file *filp, char *data, char 
> __user *udata, u32 count,
>               offset += n;
>               count -= n;
>               total += n;
> -     } while (count > 0 && n == (fid->clnt->msize - P9_IOHDRSZ));
> +     } while (count > 0 && n == fid->iounit);

If fid->iounit is zero this will go wrong. With the current version of
your server side patch, fid->iounit can be zero, right?

> 
>       if (n < 0)
>               total = n;
> @@ -187,11 +187,7 @@ v9fs_file_read(struct file *filp, char __user *udata, 
> size_t count,
>       P9_DPRINTK(P9_DEBUG_VFS, "count %zu offset %lld\n", count, *offset);
>       fid = filp->private_data;
> 
> -     if (count > (fid->clnt->msize - P9_IOHDRSZ))
> -             ret = v9fs_file_readn(filp, NULL, udata, count, *offset);
> -     else
> -             ret = p9_client_read(fid, NULL, udata, *offset, count);
> -
> +     ret = v9fs_file_readn(filp, NULL, udata, count, *offset);
>       if (ret > 0)
>               *offset += ret;
> 
> @@ -225,8 +221,6 @@ v9fs_file_write(struct file *filp, const char __user * 
> data,
>       clnt = fid->clnt;
> 
>       rsize = fid->iounit;
> -     if (!rsize || rsize > clnt->msize-P9_IOHDRSZ)
> -             rsize = clnt->msize - P9_IOHDRSZ;

This will be needed if fid->iounit = 0

Thanks,
Sripathi.
> 
>       do {
>               if (count < rsize)
> -- 
> 1.6.6.1
> 
>