Re: 2.6.0-test5-mm4 boot crash

[viro@parcelfarce.linux.theplanet.co.uk]

On Wed, Sep 24, 2003 at 11:18:47AM +0200, Helge Hafting wrote:
> Unable to handle null pointer deref at virtual address 00000000
> eip c02b7d1e  eip at md_probe

Oh, boy...  OK, I see what happens and it's _ugly_.  md_probe() is misused
there big way.  The minimal fix is to revert the cleanup in md_probe() -
replace
	int unit = *part;
with
	int unit = MINOR(dev);


However, that is crap solution.  The problem is that md_probe() is called
directly with bogus arguments - not only part is NULL (which triggers the
oops), but dev (which is supposed to be dev_t value) is actually mdidx(mddev).

Cleaner fix follows, but we really need to get the situation with gendisk
allocations into the sane shape there.  Sigh...

diff -urN B5-tty_devnum-fix/drivers/md/md.c B5-current/drivers/md/md.c
--- B5-tty_devnum-fix/drivers/md/md.c	Tue Sep 23 04:16:30 2003
+++ B5-current/drivers/md/md.c	Wed Sep 24 05:44:27 2003
@@ -1500,6 +1500,7 @@
 	mdk_rdev_t *rdev;
 	struct gendisk *disk;
 	char b[BDEVNAME_SIZE];
+	int unit;
 
 	if (list_empty(&mddev->disks)) {
 		MD_BUG();
@@ -1591,8 +1592,9 @@
 		invalidate_bdev(rdev->bdev, 0);
 	}
 
-	md_probe(mdidx(mddev), NULL, NULL);
-	disk = disks[mdidx(mddev)];
+	unit = mdidx(mddev);
+	md_probe(0, &unit, NULL);
+	disk = disks[unit];
 	if (!disk)
 		return -ENOMEM;
 
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