[PATCH 1/2] btrfs: don't read the disk superblock for zoned devices in btrfs_scratch_superblocks

[Christoph Hellwig <hch@lst.de>]

For zoned devices, btrfs_scratch_superblocks just resets the sb zones,
which means there is no need to even read the previous superblock.
Split the code to read, zero and write the superblock for convention
devices into a separate helper so that it isn't called for zoned
devices.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/btrfs/volumes.c | 51 +++++++++++++++++++++++-----------------------
 1 file changed, 26 insertions(+), 25 deletions(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index b386cb4b9aaa1..2dd7d2c5b0d80 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -2005,42 +2005,43 @@ static u64 btrfs_num_devices(struct btrfs_fs_info *fs_info)
 	return num_devices;
 }
 
+static void btrfs_scratch_superblock(struct btrfs_fs_info *fs_info,
+				     struct block_device *bdev, int copy_num)
+{
+	struct btrfs_super_block *disk_super;
+	struct page *page;
+	int ret;
+
+	disk_super = btrfs_read_dev_one_super(bdev, copy_num, false);
+	if (IS_ERR(disk_super))
+		return;
+	memset(&disk_super->magic, 0, sizeof(disk_super->magic));
+	page = virt_to_page(disk_super);
+	set_page_dirty(page);
+	lock_page(page);
+	/* write_on_page() unlocks the page */
+	ret = write_one_page(page);
+	if (ret)
+		btrfs_warn(fs_info,
+			"error clearing superblock number %d (%d)",
+			copy_num, ret);
+	btrfs_release_disk_super(disk_super);
+}
+
 void btrfs_scratch_superblocks(struct btrfs_fs_info *fs_info,
 			       struct block_device *bdev,
 			       const char *device_path)
 {
-	struct btrfs_super_block *disk_super;
 	int copy_num;
 
 	if (!bdev)
 		return;
 
 	for (copy_num = 0; copy_num < BTRFS_SUPER_MIRROR_MAX; copy_num++) {
-		struct page *page;
-		int ret;
-
-		disk_super = btrfs_read_dev_one_super(bdev, copy_num, false);
-		if (IS_ERR(disk_super))
-			continue;
-
-		if (bdev_is_zoned(bdev)) {
+		if (bdev_is_zoned(bdev))
 			btrfs_reset_sb_log_zones(bdev, copy_num);
-			continue;
-		}
-
-		memset(&disk_super->magic, 0, sizeof(disk_super->magic));
-
-		page = virt_to_page(disk_super);
-		set_page_dirty(page);
-		lock_page(page);
-		/* write_on_page() unlocks the page */
-		ret = write_one_page(page);
-		if (ret)
-			btrfs_warn(fs_info,
-				"error clearing superblock number %d (%d)",
-				copy_num, ret);
-		btrfs_release_disk_super(disk_super);
-
+		else
+			btrfs_scratch_superblock(fs_info, bdev, copy_num);
 	}
 
 	/* Notify udev that device has changed */
-- 
2.30.2