Re: [PATCH] barrier patch set

[Mika Penttilä]

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


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