Re: [PATCH] Btrfs: init device stats for new devices

[Josef Bacik <jbacik@fusionio.com>]

On Fri, Oct 11, 2013 at 03:20:42PM +0200, Stefan Behrens wrote:
> Device stats are only initialized (read from tree items) on mount.
> Trying to read device stats after adding or replacing new devices will
> return errors.
> 
> btrfs_init_new_device() and btrfs_init_dev_replace_tgtdev() are the two
> functions that allocate and initialize new btrfs_device structures after
> a filesystem is mounted. They set the device stats to zero by using
> kzalloc() which is correct for new devices. The only missing thing was
> to declare these stats as being valid (device->dev_stats_valid = 1) and
> this patch adds this missing code.
> 
> This is the reproducer:
> 
> TEST_DEV1=/dev/sdzzzzz1
> TEST_DEV2=/dev/sdzzzzz2
> TEST_DEV3=/dev/sdzzzzz3
> TEST_MNT=/mnt
> mkfs.btrfs $TEST_DEV1
> mount $TEST_DEV1 $TEST_MNT
> btrfs device add $TEST_DEV2 $TEST_MNT
> btrfs device stat $TEST_MNT
> btrfs replace start -B $TEST_DEV2 $TEST_DEV3 $TEST_MNT
> btrfs device stat $TEST_MNT
> umount $TEST_MNT
> 

Sounds like something that would look great in xfstests,

Josef