Re: [PATCH] barrier patch set

["Mika Penttilä" <mika.penttila@kolumbus.fi>]

Jens Axboe wrote:

>On Fri, Mar 19 2004, Mika Penttil? wrote:
>  
>
>>Jens Axboe wrote:
>>
>>    
>>
>>>Hi,
>>>
>>>A first release of a collected barrier patchset for 2.6.5-rc1-mm2. I
>>>have a few changes planned to support dm/md + sata, I'll do those
>>>changes over the weekend.
>>>
>>>Reiser has the best barrier support, ext3 works but only if things don't
>>>go wrong. So only attempt to use the barrier feature on ext3 if on ide
>>>drives, not SCSI nor SATA.
>>>
>>>
>>>
>>>      
>>>
>>What are these brutal pieces...?
>>
>>
>>+static int ide_transform_pc_req(ide_drive_t *drive, struct request *rq)
>>+{
>>+ if (rq->cmd[0] != 0x35) {
>>+ ide_end_request(drive, 0, 0);
>>+ return 1;
>>+ }
>>+
>>+ if (!drive->wcache) {
>>+ ide_end_request(drive, 1, 0);
>>+ return 1;
>>+ }
>>+
>>+ ide_fill_flush_cmd(drive, rq);
>>+ return 0;
>>+}
>>
>>
>>/*
>>+ * basic transformation support for scsi -> ata commands
>>+ */
>>+ if (blk_pc_request(rq)) {
>>+ if (drive->media != ide_disk)
>>+ goto kill_rq;
>>+ if (ide_transform_pc_req(drive, rq))
>>+ return ide_stopped;
>>+ }
>>    
>>
>
>Hmm, I thought it was pretty obvious, even just from the naming and
>comments. Right now, the block layer issued flush without data attached
>(ie a drive barrier without pinning it to a buffer) comes as a scsi
>synchronize cache command. I'm going to change this anyways and allow
>queue hook of a ->issue_flush_fn() that can just tailored to ide or
>scsi, _or_ dm/md and that sort of thing.
>  
>
I mean other BLOCK_PC requests than SYNCHRONIZE CACHE -> 
ide_end_request() and ide_stopped.

--Mika