lkml.org 
[lkml]   [2013]   [Mar]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [Xen-devel] [PATCH RFC 12/12] xen-block: implement indirect descriptors
On 05/03/13 15:16, Konrad Rzeszutek Wilk wrote:
> On Tue, Mar 05, 2013 at 08:11:19AM +0000, Jan Beulich wrote:
>>>>> On 04.03.13 at 21:44, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> wrote:
>>> <nods> 'op' sounds good. With a comment saying it can do all of the
>>> BLKIF_OPS_..
>>> except the BLKIF_OP_INDIRECT one. Thought one could in theory chain
>>> it that way for fun.
>>
>> In fact I'd like to exclude chaining as well as BLKIF_OP_DISCARD here.
>> The former should - if useful for anything - be controlled by a
>> separate feature flag, and the latter is plain pointless to indirect.
>> And I reckon the same would apply to BLKIF_OP_FLUSH_DISKCACHE
>> and BLKIF_OP_RESERVED_1 - i.e. it might be better to state that
>> indirection is only permitted for normal I/O (read/write) ops.
>
> <nods> That makes sense. And also of course the new BLKIF_OP should
> be documented in the Xen tree as well.

The only ops that can be done indirectly are _READ, _WRITE and
_BARRIER/_FLUSH. From the implementation in blkfront it seems like
_FLUSH/_BARRIER requests can indeed contain segments, but I haven't been
able to spot any _FLUSH op with segments on it. Can you confirm FLUSH
requests never contain bios?


\
 
 \ /
  Last update: 2013-03-05 18:21    [W:0.082 / U:0.400 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site