v4.19.13 snapshot.
diff --git a/drivers/md/bcache/writeback.h b/drivers/md/bcache/writeback.h
new file mode 100644
index 0000000..d2b9fdb
--- /dev/null
+++ b/drivers/md/bcache/writeback.h
@@ -0,0 +1,106 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _BCACHE_WRITEBACK_H
+#define _BCACHE_WRITEBACK_H
+
+#define CUTOFF_WRITEBACK 40
+#define CUTOFF_WRITEBACK_SYNC 70
+
+#define MAX_WRITEBACKS_IN_PASS 5
+#define MAX_WRITESIZE_IN_PASS 5000 /* *512b */
+
+#define WRITEBACK_RATE_UPDATE_SECS_MAX 60
+#define WRITEBACK_RATE_UPDATE_SECS_DEFAULT 5
+
+/*
+ * 14 (16384ths) is chosen here as something that each backing device
+ * should be a reasonable fraction of the share, and not to blow up
+ * until individual backing devices are a petabyte.
+ */
+#define WRITEBACK_SHARE_SHIFT 14
+
+static inline uint64_t bcache_dev_sectors_dirty(struct bcache_device *d)
+{
+ uint64_t i, ret = 0;
+
+ for (i = 0; i < d->nr_stripes; i++)
+ ret += atomic_read(d->stripe_sectors_dirty + i);
+
+ return ret;
+}
+
+static inline unsigned int offset_to_stripe(struct bcache_device *d,
+ uint64_t offset)
+{
+ do_div(offset, d->stripe_size);
+ return offset;
+}
+
+static inline bool bcache_dev_stripe_dirty(struct cached_dev *dc,
+ uint64_t offset,
+ unsigned int nr_sectors)
+{
+ unsigned int stripe = offset_to_stripe(&dc->disk, offset);
+
+ while (1) {
+ if (atomic_read(dc->disk.stripe_sectors_dirty + stripe))
+ return true;
+
+ if (nr_sectors <= dc->disk.stripe_size)
+ return false;
+
+ nr_sectors -= dc->disk.stripe_size;
+ stripe++;
+ }
+}
+
+static inline bool should_writeback(struct cached_dev *dc, struct bio *bio,
+ unsigned int cache_mode, bool would_skip)
+{
+ unsigned int in_use = dc->disk.c->gc_stats.in_use;
+
+ if (cache_mode != CACHE_MODE_WRITEBACK ||
+ test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) ||
+ in_use > CUTOFF_WRITEBACK_SYNC)
+ return false;
+
+ if (dc->partial_stripes_expensive &&
+ bcache_dev_stripe_dirty(dc, bio->bi_iter.bi_sector,
+ bio_sectors(bio)))
+ return true;
+
+ if (would_skip)
+ return false;
+
+ return (op_is_sync(bio->bi_opf) ||
+ bio->bi_opf & (REQ_META|REQ_PRIO) ||
+ in_use <= CUTOFF_WRITEBACK);
+}
+
+static inline void bch_writeback_queue(struct cached_dev *dc)
+{
+ if (!IS_ERR_OR_NULL(dc->writeback_thread))
+ wake_up_process(dc->writeback_thread);
+}
+
+static inline void bch_writeback_add(struct cached_dev *dc)
+{
+ if (!atomic_read(&dc->has_dirty) &&
+ !atomic_xchg(&dc->has_dirty, 1)) {
+ if (BDEV_STATE(&dc->sb) != BDEV_STATE_DIRTY) {
+ SET_BDEV_STATE(&dc->sb, BDEV_STATE_DIRTY);
+ /* XXX: should do this synchronously */
+ bch_write_bdev_super(dc, NULL);
+ }
+
+ bch_writeback_queue(dc);
+ }
+}
+
+void bcache_dev_sectors_dirty_add(struct cache_set *c, unsigned int inode,
+ uint64_t offset, int nr_sectors);
+
+void bch_sectors_dirty_init(struct bcache_device *d);
+void bch_cached_dev_writeback_init(struct cached_dev *dc);
+int bch_cached_dev_writeback_start(struct cached_dev *dc);
+
+#endif