Christoph Lameter wrote:
Looks like the NoNewRefs flag is mostly ==
spin_is_locked(mapping->tree_lock)? Would it not be better to check the
tree_lock?
Well there are other uses for the tree_lock (eg. tag operations)
which do not need the "no new references" guarantee.
--- linux-2.6.orig/mm/migrate.c
+++ linux-2.6/mm/migrate.c
+ SetPageNoNewRefs(page);
write_lock_irq(&mapping->tree_lock);
A dream come true! If this is really working as it sounds then we can
move the SetPageNoNewRefs up and avoid the final check under
mapping->tree_lock. Then keep SetPageNoNewRefs until the page has been
copied. It would basically play the same role as locking the page.
Yes we could do that but at this stage I wouldn't like to seperate
SetPageNoNewRefs from tree_lock, as it is replacing a traditional
guarantee that tree_lock no longer provides.
--
SUSE Labs, Novell Inc.
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