From: Nikolay Borisov <nborisov@suse.com>
Date: Tue, 14 May 2019 13:54:41 +0300
Subject: btrfs: Ensure btrfs_init_dev_replace_tgtdev sees up to date values
Git-commit: e1e0eb43ce1fd7bbdd9590715623cb3799896434
Patch-mainline: v5.3-rc1
References: bsc#1154651

btrfs_init_dev_replace_tgtdev reads certain values from the source
device (such as commit_total_bytes) which are updated during transaction
commit. Currently this function is called before committing any pending
transaction, leading to possibly reading outdated values.

Fix this by moving the function below the transaction commit, at this
point the EXCL_OP bit it set hence once transaction is complete the
total size of the device cannot be changed (it's usually changed by
resize/remove ops which are blocked).

Fixes: 9e271ae27e44 ("Btrfs: kernel operation should come after user input has been verified")
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---
 fs/btrfs/dev-replace.c |   10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

--- a/fs/btrfs/dev-replace.c
+++ b/fs/btrfs/dev-replace.c
@@ -320,11 +320,6 @@ int btrfs_dev_replace_start(struct btrfs
 	if (ret)
 		return ret;
 
-	ret = btrfs_init_dev_replace_tgtdev(fs_info, tgtdev_name,
-					    src_device, &tgt_device);
-	if (ret)
-		return ret;
-
 	/*
 	 * Here we commit the transaction to make sure commit_total_bytes
 	 * of all the devices are updated.
@@ -338,6 +333,11 @@ int btrfs_dev_replace_start(struct btrfs
 		return PTR_ERR(trans);
 	}
 
+	ret = btrfs_init_dev_replace_tgtdev(fs_info, tgtdev_name,
+					    src_device, &tgt_device);
+	if (ret)
+		return ret;
+
 	btrfs_dev_replace_write_lock(dev_replace);
 	switch (dev_replace->replace_state) {
 	case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED: