Re: [Qemu-devel] [PATCH 1/7] vnvram: VNVRAM bdrv support

[Kevin Wolf <kwolf@redhat.com>]

Am 23.05.2013 um 19:44 hat Corey Bryant geschrieben:
> Provides low-level VNVRAM functionality that reads and writes data,
> such as an entry's binary blob, to a drive image using the block
> driver.
> 
> Signed-off-by: Corey Bryant <coreyb@linux.vnet.ibm.com>

> +/*
> + * Increase the drive size if it's too small to fit the VNVRAM data
> + */
> +static int vnvram_drv_adjust_size(VNVRAM *vnvram)
> +{
> +    int rc = 0;
> +    int64_t needed_size;
> +
> +    needed_size = 0;
> +
> +    if (bdrv_getlength(vnvram->bds) < needed_size) {
> +        rc = bdrv_truncate(vnvram->bds, needed_size);
> +        if (rc != 0) {
> +            DPRINTF("%s: VNVRAM drive too small\n", __func__);
> +        }
> +    }
> +
> +    return rc;
> +}

This function doesn't make a whole lot of sense. It truncates the file
to size 0 if and only if bdrv_getlength() returns an error.

> +
> +/*
> + * Write a header to the drive with entry count of zero
> + */
> +static int vnvram_drv_hdr_create_empty(VNVRAM *vnvram)
> +{
> +    VNVRAMDrvHdr hdr;
> +
> +    hdr.version = VNVRAM_CURRENT_VERSION;
> +    hdr.magic = VNVRAM_MAGIC;
> +    hdr.num_entries = 0;
> +
> +    vnvram_drv_hdr_cpu_to_be((&hdr));
> +
> +    if (bdrv_pwrite(vnvram->bds, 0, (&hdr), sizeof(hdr)) != sizeof(hdr)) {
> +        DPRINTF("%s: Write of header to drive failed\n", __func__);
> +        return -EIO;
> +    }
> +
> +    vnvram->end_offset = sizeof(VNVRAMDrvHdr);
> +
> +    return 0;
> +}
> +
> +/*
> + * Read the header from the drive
> + */
> +static int vnvram_drv_hdr_read(VNVRAM *vnvram, VNVRAMDrvHdr *hdr)
> +{
> +    if (bdrv_pread(vnvram->bds, 0, hdr, sizeof(*hdr)) != sizeof(*hdr)) {
> +        DPRINTF("%s: Read of header from drive failed\n", __func__);
> +        return -EIO;
> +    }

Why do you turn all errors into -EIO instead of returning the real error
code? (More instances of the same thing follow)

> +
> +    vnvram_drv_hdr_be_to_cpu(hdr);
> +
> +    return 0;
> +}
> +}

Kevin