Re: bug in migrate page

[KAMEZAWA Hiroyuki]

On Wed, 22 Aug 2007 10:08:09 +0800
Shaohua Li <shaohua.li@xxxxxxxxx> wrote:

> commit dc386d4d1e98bb39fb967ee156cd456c802fc692 adds rcu_read_lock, but
> some routines in the lock range might sleep (like lock_buffer,
> aops->writepage), I saw a 'sleep in atomic' warning. It appears the
> patch has several versions before. Doing rcu_read_lock in PageAnon
> sounds break the case of PageAnon(page) && PageSwapCache(page),
> as .writepage might be called. The dummy anon patch maybe is ok.
> 

Thank you for catching.

Maybe you're correct.

BTW, in PageAnon(page) && PageSwapCache(page) case, I can't find when
.writepage is called. Could you explain ?

In my understanding,

rcu_read_lock()
	-> try_to_unmap()
	-> move_to_new_page()
		-> migrate_page() // swap has .migratepage member.
			-> migrate_page_move_mapping().
			-> migrate_page_copy().
		-> remove_migration_ptes().


At quick glance, above path has no writepage() ops.
just replace swap's radix tree entry.

Thanks,
-Kame

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/