Re: [PATCH 1/2] block: RCU protect disk->conv_zones_bitmap

[Christoph Hellwig <hch@lst.de>]

As sparse rcu warnings got in my radar for something else, I did
run sparse over this and it complains.  It will need the little
gem below to fix (and a rebase of the second patch).  Otherwise the
series looks great and way better than my initial hack, thanks!

diff --git a/block/blk-zoned.c b/block/blk-zoned.c
index 7a7855555d6d..bf4458b11720 100644
--- a/block/blk-zoned.c
+++ b/block/blk-zoned.c
@@ -350,11 +350,12 @@ int blkdev_zone_mgmt_ioctl(struct block_device *bdev, blk_mode_t mode,
 
 static inline bool disk_zone_is_conv(struct gendisk *disk, sector_t sector)
 {
+	unsigned long *bitmap;
 	bool is_conv;
 
 	rcu_read_lock();
-	is_conv = disk->conv_zones_bitmap &&
-		test_bit(disk_zone_no(disk, sector), disk->conv_zones_bitmap);
+	bitmap = rcu_dereference(disk->conv_zones_bitmap);
+	is_conv = bitmap && test_bit(disk_zone_no(disk, sector), bitmap);
 	rcu_read_unlock();
 
 	return is_conv;
@@ -1467,11 +1468,10 @@ static unsigned int disk_set_conv_zones_bitmap(struct gendisk *disk,
 	unsigned long flags;
 
 	spin_lock_irqsave(&disk->zone_wplugs_lock, flags);
+	if (bitmap)
+		nr_conv_zones = bitmap_weight(bitmap, disk->nr_zones);
 	bitmap = rcu_replace_pointer(disk->conv_zones_bitmap, bitmap,
 				     lockdep_is_held(&disk->zone_wplugs_lock));
-	if (disk->conv_zones_bitmap)
-		nr_conv_zones = bitmap_weight(disk->conv_zones_bitmap,
-					      disk->nr_zones);
 	spin_unlock_irqrestore(&disk->zone_wplugs_lock, flags);
 
 	kfree_rcu_mightsleep(bitmap);