[PATCH 10/16] btrfs-progs: preparing the latest device's superblock for commit

[Anand Jain <anand.jain@oracle.com>]

This patch provides a flag to copy the superblock of the latest device to the
fs_info::super_copy for the commit process, rather than using the superblock
from the device specified in the argument.

This serves as groundwork to enable recovery from an incomplete
btrfstune -M|m|u|U operation.

Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
 kernel-shared/disk-io.c | 3 +++
 kernel-shared/disk-io.h | 5 +++++
 2 files changed, 8 insertions(+)

diff --git a/kernel-shared/disk-io.c b/kernel-shared/disk-io.c
index 6a3178a84c88..1ef28ba33f28 100644
--- a/kernel-shared/disk-io.c
+++ b/kernel-shared/disk-io.c
@@ -1513,6 +1513,9 @@ static struct btrfs_fs_info *__open_ctree_fd(int fp, struct open_ctree_args *oca
 	if (flags & OPEN_CTREE_RECOVER_SUPER)
 		ret = btrfs_read_dev_super(fs_devices->latest_bdev, disk_super,
 				sb_bytenr, SBREAD_RECOVER);
+	else if (flags & OPEN_CTREE_USE_LATEST_BDEV)
+		ret = btrfs_read_dev_super(fs_devices->latest_bdev, disk_super,
+					   sb_bytenr, sbflags);
 	else
 		ret = btrfs_read_dev_super(fp, disk_super, sb_bytenr,
 				sbflags);
diff --git a/kernel-shared/disk-io.h b/kernel-shared/disk-io.h
index 424b953e0363..4f9ef633227d 100644
--- a/kernel-shared/disk-io.h
+++ b/kernel-shared/disk-io.h
@@ -104,6 +104,11 @@ enum btrfs_open_ctree_flags {
 	 * specific checks and only do the superficial checks.
 	 */
 	OPEN_CTREE_SKIP_LEAF_ITEM_CHECKS	= (1U << 17),
+
+	/*
+	 * Use the superblock of the latest device for the transaction commit.
+	 */
+	OPEN_CTREE_USE_LATEST_BDEV		= (1U << 18),
 };
 
 /*
-- 
2.39.3