Re: BUG?: 2.4.5 breaks reiserfs (kernel BUG)

[Alexander Viro]

On Sun, 27 May 2001, Bjerkeset, Svein Olav wrote:

> Hi,
> 
> Today I downloaded kernel 2.4.5 and compiled it. The kernel worked fine
> until
> I tried to halt the computer. When trying to unmount the reiserfs
> filesystems,
> the system freezes with the following output:
> 
> journal_begin called without kernel lock held
> kernel BUG at journal.c:423!

	Yes. My fault - badly merged patch in -pre6, actually.
Details:
	* kill_super() gets called without BKL, but doesn't grab BKL around
the calls of ->write_super() and ->put_super()
	* by the time when it calls these methods filesystem is quiet. I.e.
nothing else has a chance to touch its data structures. So actually only
reiserfs (which checks that we hold BKL) had noticed.
	* It _is_ a bug - changing locking rules is for 2.5.

Fix:
--- fs/super.c	Fri May 25 21:51:14 2001
+++ fs/super.c	Sun May 27 00:21:53 2001
@@ -873,6 +873,7 @@
 	}
 	spin_unlock(&dcache_lock);
 	down_write(&sb->s_umount);
+	lock_kernel();
 	sb->s_root = NULL;
 	/* Need to clean after the sucker */
 	if (fs->fs_flags & FS_LITTER)
@@ -901,6 +902,7 @@
 	put_filesystem(fs);
 	sb->s_type = NULL;
 	unlock_super(sb);
+	unlock_kernel();
 	up_write(&sb->s_umount);
 	if (bdev) {
 		blkdev_put(bdev, BDEV_FS);