[PATCH 4.9 72/77] bcache: fix for gc and write-back race

4.9-stable review patch. If anyone has any objections, please let me know. -- From: Tang Junhui commit 9baf30972b5568d8b5bc8b3c46a6ec5b58100463 upstream. gc and write-back get raced (see the email "bcache get stucked" I sended before): gc thread

[PATCH 4.9 72/77] bcache: fix for gc and write-back race

4.9-stable review patch. If anyone has any objections, please let me know. -- From: Tang Junhui commit 9baf30972b5568d8b5bc8b3c46a6ec5b58100463 upstream. gc and write-back get raced (see the email "bcache get stucked" I sended before): gc thread