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

[Corey Bryant]

On 05/24/2013 09:06 AM, Kevin Wolf wrote:
> 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 <address@hidden>
>
> > +/*
> > + * 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.

There's a later patch that adds a "get size" function and changes the 
initialization of needed_size to the actual size needed to store VNVRAM 
data.  Anyway I should probably just include that change in this patch. 
 I think I'll still need this function or part of it with the new 
simplified approach that it looks like we're going to take.

> > +
> > +/*
> > + * 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)

Good point, there's no reason to mask the original error code.

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

--
Regards,
Corey Bryant