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

["Cédric Le Goater" <clg@kaod.org>]

Hello Eric,

On 05/31/2016 04:36 PM, Eric Blake wrote:
> 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().

It seems that commit 243e6f69c129 ("m25p80: Switch to byte-based block access") 
is bringing another issue :

qemu-system-arm: /home/legoater/work/qemu/qemu-ast2400-mainline.git/block/io.c:1252: bdrv_aligned_pwritev: Assertion `!qiov || bytes == qiov->size' failed.
Aborted (core dumped)

The flash page size is 256. 

How should we handle this ? 

Thanks,

C.