Re: libata/sata_sil24 cache alignment problem?

[Alan Cox <alan@lxorguk.ukuu.org.uk>]

> I hadn't considered that approach due to the way the ata_port is allocated:
> 
> > libata-core.c:
> >         host = scsi_host_alloc(ent->sht, sizeof(struct ata_port));
> > 
> > hosts.c:
> > struct Scsi_Host *scsi_host_alloc(struct scsi_host_template *sht, int privsize)
> > {
> >         shost = kzalloc(sizeof(struct Scsi_Host) + privsize, gfp_mask);
> > }
> 
> The ata_port allocation is tacked onto the end of the Scsi_Host
> allocation, so the start of ata_port will only be cache aligned if the
> end of the Scsi_Host struct is, although that would be easy enough to
> fix since it's currently aligned to an unsigned long boundary.

You are right.

> I like that approach better, since it's clearer what the intent is,
> and it's easier.  Is there any other way that the ata_port struct
> might be used that would invalidate this?  

I can't think of one. The object lifetime is right - the ata_port is
created before the port buffer is used and destroyed after it is finished
(obviously or embedding it in the struct wouldn't work either)

Alan