On 19.09.2014 15:33, Paolo Bonzini wrote:
Il 19/09/2014 00:56, Peter Lieven ha scritto:
So I think if we treat it just as a hint for multiwrite, we can avoid
writing code to split oversized requests. They always worked so far, we
can certainly wait until we have a real bug fix.
I would not treat this as a hint. I would use it in cases where we definitely
know an absolute hard limit for I/O request size. Otherwise the value for
bs->bl.max_transfer_length should be 0.
If there comes in an oversized request we fail it as early as possible
That's the part that I'd rather not touch, at least not without doing
request splitting.
This series aims not at touching default behaviour. The default for
max_transfer_length
is 0 (no limit). max_transfer_length is a limit that MUST be satisfied
otherwise the request
will fail. And Patch 2 aims at catching this fail earlier in the stack.
Currently, we only
have a limit for iSCSI. Without Patch 2 it would fail after we have send the
command to
the target. And without Patch 4 it may happen that multiwrite_merge traps the
into the limit.
Maybe I should adjust the description of max_transfer_length?
Peter
