There was a possibility for infinite do-while loop inside the GC thread function in case of total failure of the caching device. I was able to reproduce it 3 times simulating disappearing of the caching device via 'echo 1 > /sys/block/<dev>/device/delete'. In that case the btree_root starts to return non zero and non -EAGAIN result, 'gc failed' message start to fill the kernel log and the do-while becomes infinite loop occupying single CPU core at 100%. There is already a logic which unregisters the cache_set (or panics) in case of io errors and thus we exit the loop here if the unregistering procedure has already started.
Signed-off-by: Pavel Vazharov <[email protected]> --- drivers/md/bcache/btree.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c index 81e8dc3..a672081 100644 --- a/drivers/md/bcache/btree.c +++ b/drivers/md/bcache/btree.c @@ -1748,8 +1748,12 @@ static void bch_btree_gc(struct cache_set *c) closure_sync(&writes); cond_resched(); - if (ret && ret != -EAGAIN) - pr_warn("gc failed!"); + if (ret && ret != -EAGAIN) { + if (test_bit(CACHE_SET_UNREGISTERING, &c->flags)) + break; + else + pr_warn("gc failed!"); + } } while (ret); bch_btree_gc_finish(c); -- 2.7.4
