clear_extent_bit() { next_node = rb_next(&state->rb_node); ... clear_state_bit(state); <-- this may free next_node if (next_node) { state = rb_entry(next_node); ... } }
clear_state_bit() calls merge_state() which may free the next node of the passing extent_state, so clear_extent_bit() may end up referencing freed memory. Signed-off-by: Li Zefan <l...@cn.fujitsu.com> --- 经过测试,发现clear_state_bit()会在80%的情况下直接把state free掉。所以之前 的比较简单的patch,会在80%的情况下重新goto回去搜索rbtree,会很慢。所以,现在 改成由clear_state_bit()返回下一个state。 --- fs/btrfs/extent_io.c | 36 +++++++++++++++++++++--------------- 1 files changed, 21 insertions(+), 15 deletions(-) diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index c968c95..20f2f5a 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -392,6 +392,15 @@ static int split_state(struct extent_io_tree *tree, struct extent_state *orig, return 0; } +static struct extent_state *next_state(struct extent_state *state) +{ + struct rb_node *next = rb_next(&state->rb_node); + if (next) + return rb_entry(next, struct extent_state, rb_node); + else + return NULL; +} + /* * utility function to clear some bits in an extent state struct. * it will optionally wake up any one waiting on this state (wake == 1) @@ -399,10 +408,11 @@ static int split_state(struct extent_io_tree *tree, struct extent_state *orig, * If no bits are set on the state struct after clearing things, the * struct is freed and removed from the tree */ -static void clear_state_bit(struct extent_io_tree *tree, - struct extent_state *state, - int *bits, int wake) +static struct extent_state *clear_state_bit(struct extent_io_tree *tree, + struct extent_state *state, + int *bits, int wake) { + struct extent_state *next; int bits_to_clear = *bits & ~EXTENT_CTLBITS; if ((bits_to_clear & EXTENT_DIRTY) && (state->state & EXTENT_DIRTY)) { @@ -415,6 +425,7 @@ static void clear_state_bit(struct extent_io_tree *tree, if (wake) wake_up(&state->wq); if (state->state == 0) { + next = next_state(state); if (state->tree) { rb_erase(&state->rb_node, &tree->state); state->tree = NULL; @@ -424,7 +435,9 @@ static void clear_state_bit(struct extent_io_tree *tree, } } else { merge_state(tree, state); + next = next_state(state); } + return next; } static struct extent_state * @@ -456,7 +469,6 @@ int clear_extent_bit(struct extent_io_tree *tree, u64 start, u64 end, struct extent_state *state; struct extent_state *cached; struct extent_state *prealloc = NULL; - struct rb_node *next_node; struct rb_node *node; u64 last_end; int err; @@ -508,14 +520,11 @@ hit_next: WARN_ON(state->end < start); last_end = state->end; - if (state->end < end && !need_resched()) - next_node = rb_next(&state->rb_node); - else - next_node = NULL; - /* the state doesn't have the wanted bits, go ahead */ - if (!(state->state & bits)) + if (!(state->state & bits)) { + state = next_state(state); goto next; + } /* * | ---- desired range ---- | @@ -569,16 +578,13 @@ hit_next: goto out; } - clear_state_bit(tree, state, &bits, wake); + state = clear_state_bit(tree, state, &bits, wake); next: if (last_end == (u64)-1) goto out; start = last_end + 1; - if (start <= end && next_node) { - state = rb_entry(next_node, struct extent_state, - rb_node); + if (start <= end && state && !need_resched()) goto hit_next; - } goto search_again; out: -- 1.7.3.1 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html