Re: [Qemu-devel] [PATCH] m25p80: fix test on blk_pread() return value

[Eric Blake <eblake@redhat.com>]

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On 05/31/2016 08:29 AM, Cédric Le Goater wrote:
> On 05/31/2016 04:26 PM, Eric Blake wrote:
>> On 05/31/2016 05:36 AM, Cédric Le Goater wrote:
>>> commit 243e6f69c129 ("m25p80: Switch to byte-based block access")
>>> replaced blk_read() calls with blk_pread() but return values are
>>> different.
>>
>> Shoot, I completely missed that when I made the conversions.  Now I need
>> to re-audit that entire series to see if the same problem happened
>> anywhere else.
> 
> I took a quick look and most of the calls to blk_pread() test with < 0. 
> So we should be fine and I should have mention that.
> 
> C. 
> 
>>>
>>> Signed-off-by: Cédric Le Goater <clg@kaod.org>
>>> ---
>>>  hw/block/m25p80.c |    2 +-
>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> Reviewed-by: Eric Blake <eblake@redhat.com>
>>
>>>
>>> Index: qemu-ast2400-mainline.git/hw/block/m25p80.c
>>> ===================================================================
>>> --- qemu-ast2400-mainline.git.orig/hw/block/m25p80.c
>>> +++ qemu-ast2400-mainline.git/hw/block/m25p80.c
>>> @@ -900,7 +900,7 @@ static int m25p80_init(SSISlave *ss)
>>>          s->storage = blk_blockalign(s->blk, s->size);
>>>  
>>>          /* FIXME: Move to late init */
>>> -        if (blk_pread(s->blk, 0, s->storage, s->size)) {
>>> +        if (blk_pread(s->blk, 0, s->storage, s->size) != s->size) {

As it is, blk_pread() (and blk_pwrite()) _always_ returns negative or
the input count value; it appears that it is incapable of reporting a
short read amount.  I guess that's intentional, but a bit odd, when
compared to the standard read()/write().

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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