On Jul 29, 2014, at 5:09 AM, Liu Bo <bo.li.liu@xxxxxxxxxx> wrote:
> Commit 49c6f736f34f901117c20960ebd7d5e60f12fcac(
> btrfs: dev replace should replace the sysfs entry) added the missing sysfs entry
> in the process of device replace, but didn't take missing devices into account,
> so now we have
>
> BUG: unable to handle kernel NULL pointer dereference at 0000000000000088
> IP: [<ffffffffa0268551>] btrfs_kobj_rm_device+0x21/0x40 [btrfs]
> ...
>
> To reproduce it,
> 1. mkfs.btrfs -f disk1 disk2
> 2. mkfs.ext4 disk1
> 3. mount disk2 /mnt -odegraded
> 4. btrfs replace start -B 1 disk3 /mnt
> --------------------------
>
> This fixes the problem.
>
> Reported-by: Chris Murphy <lists@xxxxxxxxxxxxxxxxx>
> Signed-off-by: Liu Bo <bo.li.liu@xxxxxxxxxx>
> ---
> fs/btrfs/sysfs.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
> index 7869936..12e5355 100644
> --- a/fs/btrfs/sysfs.c
> +++ b/fs/btrfs/sysfs.c
> @@ -614,7 +614,7 @@ int btrfs_kobj_rm_device(struct btrfs_fs_info *fs_info,
> if (!fs_info->device_dir_kobj)
> return -EINVAL;
>
> - if (one_device) {
> + if (one_device && one_device->bdev) {
> disk = one_device->bdev->bd_part;
> disk_kobj = &part_to_dev(disk)->kobj;
>
Applied to 3.16.0 and tested, problem is fixed.
Chris Murphy
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