If bcache device is detaching and there is no dirty data in cache,
we should send request to backing rather than get dc->count to do
cached_dev_read or cached_dev_write.
Otherwise, if there are lots of requests here to call cached_dev_get(dc),
we could never put dc->count to be 0 where calling schedule_work(&dc->detach) to finish
detaching, that means this detaching will never finish.
This commit introduce a new bit in bcache dev flags BCACHE_DEV_DETACHING_WB_DONE, this
will be set when we finish writeback in detaching and cleared in cached_dev_detach_finish().
when the request find BCACHE_DEV_DETACHING_WB_DONE is set, that means, this request should
go into backing device directly.
Signed-off-by: Dongsheng Yang <dongsheng.yang@xxxxxxxxxxxx>
---
drivers/md/bcache/bcache.h | 1 +
drivers/md/bcache/request.c | 11 ++++++++++-
drivers/md/bcache/super.c | 1 +
drivers/md/bcache/writeback.c | 7 +++++++
4 files changed, 19 insertions(+), 1 deletion(-)
diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
index 870f146..aedf211 100644
--- a/drivers/md/bcache/bcache.h
+++ b/drivers/md/bcache/bcache.h
@@ -265,6 +265,7 @@ struct bcache_device {
#define BCACHE_DEV_UNLINK_DONE 2
#define BCACHE_DEV_WB_RUNNING 3
#define BCACHE_DEV_RATE_DW_RUNNING 4
+#define BCACHE_DEV_DETACHING_WB_DONE 5
int nr_stripes;
unsigned int stripe_size;
atomic_t *stripe_sectors_dirty;
diff --git a/drivers/md/bcache/request.c b/drivers/md/bcache/request.c
index c7cadaa..94c44f2 100644
--- a/drivers/md/bcache/request.c
+++ b/drivers/md/bcache/request.c
@@ -1194,7 +1194,16 @@ blk_qc_t cached_dev_submit_bio(struct bio *bio)
bio_set_dev(bio, dc->bdev);
bio->bi_iter.bi_sector += dc->sb.data_offset;
- if (cached_dev_get(dc)) {
+ /*
+ * If BCACHE_DEV_DETACHING_WB_DONE is set,
+ * we should send request to backing rather than get dc->count to do
+ * cached_dev_read or cached_dev_write. Otherwise, if there are lots
+ * of requests here to call cached_dev_get(dc), we could never put
+ * dc->count to be 0 where calling schedule_work(&dc->detach) to finish
+ * detaching, that means this detaching will never finish.
+ */
+ if (!test_bit(BCACHE_DEV_DETACHING_WB_DONE, &dc->disk.flags) &&
+ cached_dev_get(dc)) {
s = search_alloc(bio, d);
trace_bcache_request_start(s->d, bio);
diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index 9298fc7..3c32ddb 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -1147,6 +1147,7 @@ static void cached_dev_detach_finish(struct work_struct *w)
bcache_device_detach(&dc->disk);
list_move(&dc->list, &uncached_devices);
+ clear_bit(BCACHE_DEV_DETACHING_WB_DONE, &dc->disk.flags);
clear_bit(BCACHE_DEV_DETACHING, &dc->disk.flags);
clear_bit(BCACHE_DEV_UNLINK_DONE, &dc->disk.flags);
diff --git a/drivers/md/bcache/writeback.c b/drivers/md/bcache/writeback.c
index 2cd0340..6799f99 100644
--- a/drivers/md/bcache/writeback.c
+++ b/drivers/md/bcache/writeback.c
@@ -714,6 +714,13 @@ static int bch_writeback_thread(void *arg)
bch_write_bdev_super(dc, &cl);
closure_sync(&cl);
+ /*
+ * BCACHE_DEV_DETACHING_WB_DONE will tell
+ * request should be sent directly to backing
+ * device directly, without getting dc->count.
+ */
+ set_bit(BCACHE_DEV_DETACHING_WB_DONE,
+ &dc->disk.flags);
up_write(&dc->writeback_lock);
break;
}
--
1.8.3.1
