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Btrfs: fix unsafe usage of merge_state

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merge_state can free the current state if it can be merged with the next node,
but in set_extent_bit(), after merge_state, we still use the current extent to
get the next node and cache it into cached_state

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
This commit is contained in:
Xiao Guangrong
2011-04-20 06:45:49 +00:00
committed by Chris Mason
parent 8233767a22
commit c7f895a2b2
1 changed files with 14 additions and 8 deletions
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22
fs/btrfs/extent_io.c
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@@ -780,20 +780,18 @@ hit_next:
if (err) if (err)
goto out; goto out;
next_node = rb_next(node);
cache_state(state, cached_state); cache_state(state, cached_state);
merge_state(tree, state); merge_state(tree, state);
if (last_end == (u64)-1) if (last_end == (u64)-1)
goto out; goto out;
start = last_end + 1; start = last_end + 1;
if (start < end && prealloc && !need_resched()) { if (next_node && start < end && prealloc && !need_resched()) {
next_node = rb_next(node); state = rb_entry(next_node, struct extent_state,
if (next_node) { rb_node);
state = rb_entry(next_node, struct extent_state, if (state->start == start)
rb_node); goto hit_next;
if (state->start == start)
goto hit_next;
}
} }
goto search_again; goto search_again;
} }
@@ -856,14 +854,22 @@ hit_next:
prealloc = alloc_extent_state_atomic(prealloc); prealloc = alloc_extent_state_atomic(prealloc);
BUG_ON(!prealloc); BUG_ON(!prealloc);
/*
* Avoid to free 'prealloc' if it can be merged with
* the later extent.
*/
atomic_inc(&prealloc->refs);
err = insert_state(tree, prealloc, start, this_end, err = insert_state(tree, prealloc, start, this_end,
&bits); &bits);
BUG_ON(err == -EEXIST); BUG_ON(err == -EEXIST);
if (err) { if (err) {
free_extent_state(prealloc);
prealloc = NULL; prealloc = NULL;
goto out; goto out;
} }
cache_state(prealloc, cached_state); cache_state(prealloc, cached_state);
free_extent_state(prealloc);
prealloc = NULL; prealloc = NULL;
start = this_end + 1; start = this_end + 1;
goto search_again; goto search_again;