[PATCH 2/6] btrfs: metadata_uuid: move split-brain handling from fs_id() to new function

[damenly.su@gmail.com]

From: Su Yue <Damenly_Su@gmx.com>

The parameter @metadata_fsid of fs_id() is not NULL while scanned device
has metadata_uuid but not changing. Obviously, the cases handling part
in fs_id() is for this situation. Move the logic into new function
find_fsid_changing_metadata_uuid().

Signed-off-by: Su Yue <Damenly_Su@gmx.com>
---
 fs/btrfs/volumes.c | 78 ++++++++++++++++++++++++----------------------
 1 file changed, 41 insertions(+), 37 deletions(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 9efa4123c335..b08b06a89a77 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -438,40 +438,6 @@ static noinline struct btrfs_fs_devices *find_fsid(
 
 	ASSERT(fsid);
 
-	if (metadata_fsid) {
-		/*
-		 * Handle scanned device having completed its fsid change but
-		 * belonging to a fs_devices that was created by first scanning
-		 * a device which didn't have its fsid/metadata_uuid changed
-		 * at all and the CHANGING_FSID_V2 flag set.
-		 */
-		list_for_each_entry(fs_devices, &fs_uuids, fs_list) {
-			if (fs_devices->fsid_change &&
-			    memcmp(metadata_fsid, fs_devices->fsid,
-				   BTRFS_FSID_SIZE) == 0 &&
-			    memcmp(fs_devices->fsid, fs_devices->metadata_uuid,
-				   BTRFS_FSID_SIZE) == 0) {
-				return fs_devices;
-			}
-		}
-		/*
-		 * Handle scanned device having completed its fsid change but
-		 * belonging to a fs_devices that was created by a device that
-		 * has an outdated pair of fsid/metadata_uuid and
-		 * CHANGING_FSID_V2 flag set.
-		 */
-		list_for_each_entry(fs_devices, &fs_uuids, fs_list) {
-			if (fs_devices->fsid_change &&
-			    memcmp(fs_devices->metadata_uuid,
-				   fs_devices->fsid, BTRFS_FSID_SIZE) != 0 &&
-			    memcmp(metadata_fsid, fs_devices->metadata_uuid,
-				   BTRFS_FSID_SIZE) == 0) {
-				return fs_devices;
-			}
-		}
-	}
-
-	/* Handle non-split brain cases */
 	list_for_each_entry(fs_devices, &fs_uuids, fs_list) {
 		if (metadata_fsid) {
 			if (memcmp(fsid, fs_devices->fsid, BTRFS_FSID_SIZE) == 0
@@ -712,6 +678,46 @@ static struct btrfs_fs_devices *find_fsid_changed(
 
 	return NULL;
 }
+
+static struct btrfs_fs_devices *find_fsid_changing_metada_uuid(
+					struct btrfs_super_block *disk_super)
+{
+	struct btrfs_fs_devices *fs_devices;
+
+	/*
+	 * Handle scanned device having completed its fsid change but
+	 * belonging to a fs_devices that was created by first scanning
+	 * a device which didn't have its fsid/metadata_uuid changed
+	 * at all and the CHANGING_FSID_V2 flag set.
+	 */
+	list_for_each_entry(fs_devices, &fs_uuids, fs_list) {
+		if (fs_devices->fsid_change &&
+		    memcmp(disk_super->metadata_uuid, fs_devices->fsid,
+			   BTRFS_FSID_SIZE) == 0 &&
+		    memcmp(fs_devices->fsid, fs_devices->metadata_uuid,
+			   BTRFS_FSID_SIZE) == 0) {
+			return fs_devices;
+		}
+	}
+	/*
+	 * Handle scanned device having completed its fsid change but
+	 * belonging to a fs_devices that was created by a device that
+	 * has an outdated pair of fsid/metadata_uuid and
+	 * CHANGING_FSID_V2 flag set.
+	 */
+	list_for_each_entry(fs_devices, &fs_uuids, fs_list) {
+		if (fs_devices->fsid_change &&
+		    memcmp(fs_devices->metadata_uuid,
+			   fs_devices->fsid, BTRFS_FSID_SIZE) != 0 &&
+		    memcmp(disk_super->metadata_uuid, fs_devices->metadata_uuid,
+			   BTRFS_FSID_SIZE) == 0) {
+			return fs_devices;
+		}
+	}
+
+	return find_fsid(disk_super->fsid, disk_super->metadata_uuid);
+}
+
 /*
  * Add new device to list of registered devices
  *
@@ -751,13 +757,11 @@ static noinline struct btrfs_device *device_list_add(const char *path,
 			fs_devices = find_fsid_changed(disk_super);
 		}
 	} else if (has_metadata_uuid) {
-		fs_devices = find_fsid(disk_super->fsid,
-				       disk_super->metadata_uuid);
+		fs_devices = find_fsid_changing_metada_uuid(disk_super);
 	} else {
 		fs_devices = find_fsid(disk_super->fsid, NULL);
 	}
 
-
 	if (!fs_devices) {
 		if (has_metadata_uuid)
 			fs_devices = alloc_fs_devices(disk_super->fsid,
-- 
2.21.0 (Apple Git-122.2)