bcache: Better full stripe scanning

The old scanning-by-stripe code burned too much CPU, this should be
better.

Signed-off-by: Kent Overstreet <kmo@daterainc.com>

1 files changed, 13 insertions, 8 deletions

diff --git a/drivers/md/bcache/writeback.h b/drivers/md/bcache/writeback.h
index 60516bfa6052..fe7d9d56492b 100644
--- a/drivers/md/bcache/writeback.h
+++ b/drivers/md/bcache/writeback.h
@@ -14,22 +14,27 @@ static inline uint64_t bcache_dev_sectors_dirty(struct bcache_device *d)
 	return ret;
 }
 
-static inline bool bcache_dev_stripe_dirty(struct bcache_device *d,
+static inline unsigned 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 nr_sectors)
 {
-	uint64_t stripe = offset;
-
-	do_div(stripe, d->stripe_size);
+	unsigned stripe = offset_to_stripe(&dc->disk, offset);
 
 	while (1) {
-		if (atomic_read(d->stripe_sectors_dirty + stripe))
+		if (atomic_read(dc->disk.stripe_sectors_dirty + stripe))
 			return true;
 
-		if (nr_sectors <= d->stripe_size)
+		if (nr_sectors <= dc->disk.stripe_size)
 			return false;
 
-		nr_sectors -= d->stripe_size;
+		nr_sectors -= dc->disk.stripe_size;
 		stripe++;
 	}
 }
@@ -45,7 +50,7 @@ static inline bool should_writeback(struct cached_dev *dc, struct bio *bio,
 		return false;
 
 	if (dc->partial_stripes_expensive &&
-	    bcache_dev_stripe_dirty(&dc->disk, bio->bi_sector,
+	    bcache_dev_stripe_dirty(dc, bio->bi_sector,
 				    bio_sectors(bio)))
 		return true;