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SubjectRe: debugging patch for ide-cd/isofs
After a bit more thought, I was missing something.  It seems it is
hanging somewhere after it returns from the ide-cd and cdrom routines
and in fs/devices:check_disk_change(). OK, I think I know what is
going on. If either an error occurs when trying to detect a disk
change or a disk is actually changed, it falls through to the next
operation instead of returning. The next operation happens to be
a get_super(), but the superblock is already locked in isofs_read_super(),
so we hang.

Bill, this makes perfect sense when looking at your changes. Previously,
the superblock was unlocked before calling check_disk_change(). Now,
it is unlocked after calling check_disk_change(). With all the
reordering you've done with error conditions, I'm not sure how you
want to handle this one. As a test to make sure this is indeed the
case, apply this pseudo patch to your fs/isofs/inode.c:

+unlock_super(s);
printk("isofs_read_super: checking disk change\n");
if(!check_disk_change(dev)) {
printk("isofs_read_super: calling unlock_super\n");
/* turn off ide-cd debugging */
ide_cd_debug = 0;
- unlock_super(s);
printk("isofs_read_super: unlock_super done\n");
return s;
}
+lock_super(s);
printk("isofs_read_super: disk change failed!\n");

It should fix the problem. It would seem to me there is something a
bit wrong in check_disk_change(). If it gets an error as it appears
to in this case, it assumes the disk has been changed. Should the
check be instead:

if (fops->check_media_change(dev) <= 0)
return 0;

?

Erik, the ide-cd code is completely clear of any blame.

- Gordon

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