Re: Possible dcache BUG

[Gene Heskett]

On Friday 13 August 2004 22:18, Marcelo Tosatti wrote:
[...]
>
>Hi fellows,
>
>I've taken some time to look at this oopses, and I truly believe we
>are facing real corruption.
>
>The symptom is that an inode's (blockdev) i_mapping->private_list
> gets corrupted, one of its buffer_head's contains a b_assoc_mapping
> list_head with NULL pointers.
>
>And this is not an SMP race, because Gene is not running SMP.
>
>Gene's oops happens when remove_inode_buffers calls 
> __remove_assoc_queue(bh)
>
>Ingo's oops happens while remove_inode_buffers does
>
> struct buffer_head *bh = BH_ENTRY(list->next);
>
>which is
>
>	mov ffffffd8(%ecx), (%somewhere)
>
>%ecx is zero, so...
>
>There is a bug somewhere.
>
>--- a/fs/buffer.c.original	2004-08-14 00:19:55.000000000 -0300
>+++ b/fs/buffer.c	2004-08-14 00:34:57.000000000 -0300
>@@ -802,6 +802,8 @@
>  */
> static inline void __remove_assoc_queue(struct buffer_head *bh)
> {
>+	BUG_ON(bh->b_assoc_buffers.next == NULL);
>+	BUG_ON(bh->b_assoc_buffers.prev == NULL);
> 	list_del_init(&bh->b_assoc_buffers);
> }
>
>@@ -1073,6 +1075,7 @@
>
> 		spin_lock(&buffer_mapping->private_lock);
> 		while (!list_empty(list)) {
>+			BUG_ON(list->next == NULL);
> 			struct buffer_head *bh = BH_ENTRY(list->next);
During the compile, the above line output this warning:
fs/buffer.c: In function `remove_inode_buffers':
fs/buffer.c:1079: warning: ISO C90 forbids mixed declarations and code
Did the compiler do the right thing?  Or is this perchance the bug?
> 			if (buffer_dirty(bh)) {
> 				ret = 0;

In any event, its getting sleepy out, good night all.

-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
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by Gene Heskett are:
Copyright 2004 by Maurice Eugene Heskett, all rights reserved.
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