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mm: readahead scan lockless 

radix_tree_next_hole() is implemented as a series of radix_tree_lookup()s.
So it can be called locklessly, under rcu_read_lock().

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Nick Piggin 2008-07-25 19:45:28 -07:00 committed by Linus Torvalds
parent 652ea69536
commit 30002ed2e4
1 changed files with 3 additions and 3 deletions
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6
mm/readahead.c
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@ -382,9 +382,9 @@ ondemand_readahead(struct address_space *mapping,
if (hit_readahead_marker) {
pgoff_t start;
read_lock_irq(&mapping->tree_lock);
start = radix_tree_next_hole(&mapping->page_tree, offset, max+1);
read_unlock_irq(&mapping->tree_lock);
rcu_read_lock();
start = radix_tree_next_hole(&mapping->page_tree, offset,max+1);
rcu_read_unlock();
if (!start || start - offset > max)
return 0;