Re: [Xen-devel] [PATCH 2/12] VTPM mini-os: posix IO layer for blkfront in mini-os

[Samuel Thibault <samuel.thibault@xxxxxxxxxxxx>]

Matthew Fioravante, le Fri 11 Mar 2011 17:34:26 -0500, a écrit :
> +      /*Make sure we have write permission */
> +      if(dev->info.info & VDISK_READONLY || dev->info.mode != O_RDWR) {

O_WRONLY too.

> +   aiocb.aio_dev = dev;
> +   aiocb.aio_buf = _xmalloc(blocksize, dev->info.sector_size);
> +   aiocb.aio_nbytes = blocksize;
> +   aiocb.aio_offset = blknum * blocksize;
> +   aiocb.aio_cb = NULL;
> +   aiocb.data = NULL;
> +

> +      /* read operation */
> +      if(!write) {
> +      aiocb.aio_cb = NULL;
> +      blkfront_read(&aiocb);
> +      memcpy(buf, &aiocb.aio_buf[blkoff], bytes);
> +      } 

Could you perhaps optimize when buf is actually aligned?  That would
save a copy.

> +      /* Write operation */
> +      else {
> +      /* If we're writing a partial block, we need to read the current 
> contents first
> +       * so we don't overwrite the extra bits with garbage */
> +      if(blkoff != 0 || bytes < blocksize) {
> +         aiocb.aio_cb = NULL;

Maybe blkfront_aio_cb should do it itself?  It looks odd to have to do
it when reusing an aiocb structure.

Apart from that it looks good.

Samuel

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