On Tue, 2009-08-25 at 21:44 +0200, Arkadiusz Miskiewicz wrote:
> On Tuesday 25 of August 2009, James Bottomley wrote:
> > On Tue, 2009-08-25 at 21:24 +0200, Arkadiusz Miskiewicz wrote:
> > > What could be the reason for scsi_wait_scan not waiting untill all disks
> > > are found?
> > >
> > > I'm testing 2.6.30.5 on hardware with LSI Logic / Symbios Logic MegaRAID
> > > 530 SCSI 320-0X RAID controller and modprobe scsi_wait_scan finishes
> > > earlier than disks are found.
> > >
> > > My initrd (romfs) does:
> > > insmod /lib/modules/2.6.30.5-0.3/kernel/drivers/scsi/scsi_mod.ko
> > > insmod
> > > /lib/modules/2.6.30.5-0.3/kernel/drivers/scsi/megaraid/megaraid_mm.ko
> > > insmod
> > > /lib/modules/2.6.30.5-0.3/kernel/drivers/scsi/megaraid/megaraid_mbox.ko
> > > insmod /lib/modules/2.6.30.5-0.3/kernel/lib/crc-t10dif.ko
> > > insmod /lib/modules/2.6.30.5-0.3/kernel/drivers/scsi/sd_mod.ko
> > > insmod /lib/modules/2.6.30.5-0.3/kernel/drivers/scsi/scsi_wait_scan.ko
> > > insmod /lib/modules/2.6.30.5-0.3/kernel/fs/exportfs/exportfs.ko
> > > insmod /lib/modules/2.6.30.5-0.3/kernel/fs/xfs/xfs.ko
> > > if [ "${ROOT##/dev/}" != "${ROOT}" ]; then
> > > rootnr="$(busybox awk -v rootnode="${ROOT##/dev/}" '$4 == rootnode {
> > > print 256 * $1 + $2 }' /proc/partitions)"
> > > if [ -n "$rootnr" ]; then
> > > echo "$rootnr" > /proc/sys/kernel/real-root-dev
> > > fi
> > >
> > >
> > > Now if I add sleep few seconds or /bin/sh at the end of this initrd, then
> > > boot and then disks are detected properly and rootfs is mounted properly
> > > (after I exit from sh in case when /bin/sh is used).
> > >
> > > The question remains - why scsi_wait_scan doesn't wait?
> >
> > It's caused by the sd async patches. What's happening is wait_scan is
> > waiting until all the scans are complete, but now sd attachment may not
> > be completed by the time that happens. So, although you have a scanned
> > disk, you can't mount it without and attached sd driver.
>
> > Hopefully when
> > all initrds are configured to wait until root appears, this problem will
> > go away.
>
> Uh, ugly. I'll disable SCSI_SCAN_ASYNC here then.
That won't actually help: the sd async scan is a separate mechanism not
tied to that variable
> Anyway what's the point of scsi_wait_scan module if initrd is still required
> to wait until root appears? (unless current behaviour is broken behaviour
> meant to be fixed?)
It was supposed to be an interim measure until the ditributions got
their act together for initrd booting by waiting for the root disk to
appear. It's just been "interim" for a bit longer than expected.
James
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