Re: scsi_wait_scan not working (2.6.30.5)

[Arkadiusz Miskiewicz <a.miskiewicz@gmail.com>]

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.

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?)

Thanks!

> James

-- 
Arkadiusz Miśkiewicz        PLD/Linux Team
arekm / maven.pl            http://ftp.pld-linux.org/
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