Re: back-trace on mounting ide cd-rom

[Andrew Morton <akpm@digeo.com>]

Robert Love <rml@tech9.net> wrote:
>
> I got the following errors and back-trace upon mounting my IDE CD-ROM
> (hdc).  It seems to be a normal ISO9660... its the Red Hat 9 CD.
> 
> I haven't looked into it yet.  Not sure why there is ext3 stuff in
> there... maybe the CD-ROM mount is unrelated?  Mounting the CD
> subsequent times is OK.
> 
> Kernel is 2.5.66-mm2.  UP, preempt, no highmem, i686.
> 
> Here we go:
> 
>         buffer layer error at fs/buffer.c:127

ah, my new debug code is buggy.  It is legal to wait upon a zero-ref buffer
if that buffer's page is locked.

diff -puN fs/buffer.c~a fs/buffer.c
--- 25/fs/buffer.c~a	Wed Apr  2 15:41:25 2003
+++ 25-akpm/fs/buffer.c	Wed Apr  2 15:43:02 2003
@@ -123,7 +123,8 @@ void __wait_on_buffer(struct buffer_head
 	wait_queue_head_t *wqh = bh_waitq_head(bh);
 	DEFINE_WAIT(wait);
 
-	if (atomic_read(&bh->b_count) == 0)
+	if (atomic_read(&bh->b_count) == 0 &&
+			(!bh->b_page || !PageLocked(bh->b_page)))
 		buffer_error();
 
 	do {

_