Re: MDADM 3.3 broken?

[NeilBrown <neilb@suse.de>]

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On Tue, 19 Nov 2013 20:45:47 +0100 Martin Wilck <mwilck@arcor.de> wrote:

> On 11/19/2013 01:01 AM, NeilBrown wrote:
> > On Mon, 18 Nov 2013 15:13:58 -0800 "David F." <df7729@gmail.com> wrote:
> > 
> > 
> >> output of 'mdadm --assemble --scan --no-degraded -v' (mdadm 3.2.6):
> > ...
> >> mdadm: no RAID superblock on /dev/sdc2
> > 
> > 
> > 
> >>
> >> output1 of 'mdadm --assemble --scan --no-degraded -v' (mdadm 3.3 -
> >> note using /dev/sdc2, not /dev/sdc):
> > .....
> >> mdadm: /dev/sdc2 is identified as a member of /dev/md/imsm0, slot -1.
> > 
> > So there is the problem.  mdadm 3.2.6 sees no RAID superblock on sdc2, while
> > mdadm 3.3 does (but should not).
> > 
> > 
> > However that code hasn't changed!
> > 
> > load_super_imsm() still starts with:
> > 
> > 
> > 	if (test_partition(fd))
> > 		/* IMSM not allowed on partitions */
> > 		return 1;
> 
> Well not quite - you changed that code in commit b31df436 "intel,ddf:
> don't require partitions when ignore_hw_compat is set". Maybe there's
> something wrong with that ignore_hw_compat logic?
> 
> In the strace I don't see indication of test_partition having been
> called, that's another hint in that direction.
> 

Yes... I seems I was accidentally looking at an old version of mdadm.

I've just committed the following patch which should fix the problem.

(git clone git://neil.brown.name/mdadm/ ; cd mdadm ; make;make install)

Thanks,
NeilBrown

From 357ac1067835d1cdd5f80acc28501db0ffc64957 Mon Sep 17 00:00:00 2001
From: NeilBrown <neilb@suse.de>
Date: Wed, 20 Nov 2013 10:49:14 +1100
Subject: [PATCH] IMSM metadata really should be ignored when found on
 partitions.

commit b31df43682216d1c65813eae49ebdd8253db8907
changed load_super_imsm to not insist on finding a partition if
ignore_hw_compat was set.
Unfortunately this is set for '--assemble' so arrays could get
assembled badly.

The comment says this was to allow e.g. --examine of image files.
A better fixes for this is to change test_partitions to not report
a regular file as being a partition.
The errors from the BLKPG ioctl are:

 ENOTTY : not a block device.
 EINVAL : not a whole device (probably a partition)
 ENXIO  : partition doesn't exist (so not a partition)

Reported-by: "David F." <df7729@gmail.com>
Signed-off-by: NeilBrown <neilb@suse.de>

diff --git a/super-intel.c b/super-intel.c
index 7b2406866493..c103ffdd2dd8 100644
--- a/super-intel.c
+++ b/super-intel.c
@@ -4423,7 +4423,7 @@ static int load_super_imsm(struct supertype *st, int fd, char *devname)
 	struct intel_super *super;
 	int rv;
 
-	if (!st->ignore_hw_compat && test_partition(fd))
+	if (test_partition(fd))
 		/* IMSM not allowed on partitions */
 		return 1;
 
diff --git a/util.c b/util.c
index 5f95f1f97c02..b29a3ee7ce47 100644
--- a/util.c
+++ b/util.c
@@ -307,7 +307,7 @@ int test_partition(int fd)
 	if (ioctl(fd, BLKPG, &a) == 0)
 		/* Very unlikely, but not a partition */
 		return 0;
-	if (errno == ENXIO)
+	if (errno == ENXIO || errno == ENOTTY)
 		/* not a partition */
 		return 0;
 

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