Re: [Qemu-devel] [PATCH] block: fix big write

[Paolo Bonzini]

On 10/12/2014 13:23, Ming Lei wrote:
>> >
>> > Again, we're talking of 2GB and this is something that should never
>> > happen in practice.
> Again, the 2GB limit can be avoided if I/O is splitted, isn't it?

Sure.  The guest kernel is doing the split.

> It is _not_ never happen at all, and easy to be triggered when using
> mkfs.

mkfs is not something to optimize for, it's just something that should
work.  (Also, some hardware may time out if you do write same with too
high a block count).

Both Linux and Windows will always use UNMAP on QEMU, except for the
small time period where Linux used WRITE SAME and this bug was
discovered.  And all versions of Linux that used WRITE SAME honored the
max_ws_blocks field.

Paolo