On 2/11/22 2:39 PM, mingzhe.zou@xxxxxxxxxxxx wrote:
From: Mingzhe Zou <mingzhe.zou@xxxxxxxxxxxx>
When multiple threads to check btree nodes in parallel, the main
thread wait for all threads to stop or CACHE_SET_IO_DISABLE flag:
wait_event_interruptible(check_state->wait,
atomic_read(&check_state->started) == 0 ||
test_bit(CACHE_SET_IO_DISABLE, &c->flags));
However, the bch_btree_node_read and bch_btree_node_read_done
maybe call bch_cache_set_error, then the CACHE_SET_IO_DISABLE
will be set. If the flag already set, the main thread return
error. At the same time, maybe some threads still running and
read NULL pointer, the kernel will crash.
Hi Mingzhe,
Could you please explain a bit more about "read NULL pointer"? Which
NULL pointer might be read in the above condition?
Thanks.
Coly Li
This patch change the event wait condition, the main thread must
wait for all threads to stop.
Signed-off-by: Mingzhe Zou <mingzhe.zou@xxxxxxxxxxxx>
---
drivers/md/bcache/btree.c | 6 ++++--
drivers/md/bcache/writeback.c | 6 ++++--
2 files changed, 8 insertions(+), 4 deletions(-)
diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
index 88c573eeb598..ad9f16689419 100644
--- a/drivers/md/bcache/btree.c
+++ b/drivers/md/bcache/btree.c
@@ -2060,9 +2060,11 @@ int bch_btree_check(struct cache_set *c)
}
}
+ /*
+ * Must wait for all threads to stop.
+ */
wait_event_interruptible(check_state->wait,
- atomic_read(&check_state->started) == 0 ||
- test_bit(CACHE_SET_IO_DISABLE, &c->flags));
+ atomic_read(&check_state->started) == 0);
for (i = 0; i < check_state->total_threads; i++) {
if (check_state->infos[i].result) {
diff --git a/drivers/md/bcache/writeback.c b/drivers/md/bcache/writeback.c
index c7560f66dca8..68d3dd6b4f11 100644
--- a/drivers/md/bcache/writeback.c
+++ b/drivers/md/bcache/writeback.c
@@ -998,9 +998,11 @@ void bch_sectors_dirty_init(struct bcache_device *d)
}
}
+ /*
+ * Must wait for all threads to stop.
+ */
wait_event_interruptible(state->wait,
- atomic_read(&state->started) == 0 ||
- test_bit(CACHE_SET_IO_DISABLE, &c->flags));
+ atomic_read(&state->started) == 0);
out:
kfree(state);
