2.4: crash when unmounting ext2fs

From: linas@austin.ibm.com
Date: Wed Apr 16 2003 - 12:43:54 EST


Hi,
                                                                                
I've been chasing a bug in a slightly down-level version of the
kernel (2.4.19) and was wondering if perchance its been fixed
recently ... The crash occurs after a large ext2 filesystem
was heavily used (in a large-memory config), and is then unmounted.
Using KDB, I find myself chasing pointers in discard_bh_page()
(in fs/buffer.c) and one of the bh->b_this_page points at a page
that's clearly been zero'ed, but for one tell-tale clue. It looks
like the zero'ed out page used to be chained correctly into the
lru_list[], and then it was zero'ed out, and then someone called
__remove_from_lru_list() on its neighbor.
                                                                                
I'm a little stumped on how a bh was on the lru_list, got whacked,
and is still in the list of page->buffers that discard_bh_page() is
trying to get rid of. Anyone fix anything like this recently?

Or more generally, any sort of buffer-freeing/page-freeing/file-system
flushing/freeing type bugs where pages might have been zero'ed out
before thier time?

--linas
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