From 3985fb80d0d37810e55ef328c9c406d0e963c444 Mon Sep 17 00:00:00 2001
From: Nikolay Borisov <nborisov@suse.com>
Date: Wed, 10 Oct 2018 12:48:41 +0300
Subject: [PATCH 4/6] btrfs: Introduce 2 more members to struct
btrfs_fs_devices
References: fate#325871
Patch-mainline: Submitted, awaiting review
In order to gracefully handle split-brain scenario which are very
unlikely, yet possible, while performing the FSID change I'm
gonna need two more pieces of information:
1. The highest generation number among all devices registered to a
particular btrfs_fs_devices
2. A boolean flag whether a given btrfs_fs_devices was created by a
device which had the FSID_CHANGING_V2 flag set.
This is a preparatory patch and just introduces the variables as well
as code which sets them, their actual use is going to happen in a later
patch.
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
---
fs/btrfs/volumes.c | 9 ++++++++-
fs/btrfs/volumes.h | 4 ++++
2 files changed, 12 insertions(+), 1 deletion(-)
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -634,6 +634,8 @@ static noinline int device_list_add(cons
u64 found_transid = btrfs_super_generation(disk_super);
bool has_metadata_uuid = (btrfs_super_incompat_flags(disk_super) &
BTRFS_FEATURE_INCOMPAT_METADATA_UUID);
+ bool fsid_change_in_progress = (btrfs_super_flags(disk_super) &
+ BTRFS_SUPER_FLAG_CHANGING_FSID_V2);
if (has_metadata_uuid)
fs_devices = find_fsid(disk_super->fsid, disk_super->metadata_uuid);
@@ -650,6 +652,8 @@ static noinline int device_list_add(cons
if (IS_ERR(fs_devices))
return PTR_ERR(fs_devices);
+ fs_devices->fsid_change = fsid_change_in_progress;
+
list_add(&fs_devices->list, &fs_uuids);
device = NULL;
@@ -738,8 +742,11 @@ static noinline int device_list_add(cons
* it back. We need it to pick the disk with largest generation
* (as above).
*/
- if (!fs_devices->opened)
+ if (!fs_devices->opened) {
device->generation = found_transid;
+ fs_devices->latest_generation = max(found_transid,
+ fs_devices->latest_generation);
+ }
/*
* if there is new btrfs on an already registered device,
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -220,6 +220,7 @@ BTRFS_DEVICE_GETSET_FUNCS(bytes_used);
struct btrfs_fs_devices {
u8 fsid[BTRFS_FSID_SIZE]; /* FS specific uuid */
u8 metadata_uuid[BTRFS_FSID_SIZE];
+ bool fsid_change;
u64 num_devices;
u64 open_devices;
@@ -229,6 +230,9 @@ struct btrfs_fs_devices {
u64 total_devices;
struct block_device *latest_bdev;
+ /* Highest generation number of seen devices */
+ u64 latest_generation;
+
/* all of the devices in the FS, protected by a mutex
* so we can safely walk it to write out the supers without
* worrying about add/remove by the multi-device code.