Re: [PATCH] mdadm/super1: restore commit 45a87c2f31335 to fix clustered slot issue

[Coly Li <colyli@suse.de>]

On 4/1/22 2:18 PM, Heming Zhao wrote:
> Commit 9d67f6496c71 ("mdadm:check the nodes when operate clustered
> array") modified assignment logic for st->nodes in write_bitmap1(),
> which introduced bitmap slot issue:
>
> load_super1 didn't set up supertype.nodes, which made spare disk only
> have one slot info. Then it triggered kernel md_bitmap_load_sb to get
> wrong bitmap slot data.
>
> For fixing this issue, there are two methods:
>
> 1> revert the related code of commit 9d67f6496c71. and restore the code
>     from former commit 45a87c2f31335 ("super1: add more checks for
>     NodeNumUpdate option").
>     st->nodes value would be 0 & 1 under current code logic. i.e.
>     When adding a spare disk, there is no place to init st->nodes, and
>     the value is ZERO.
>
> 2> keep 9d67f6496c71, add additional ->nodes handling in load_super1(),
>     let load_super1 to set st->nodes when bitmap is BITMAP_MAJOR_CLUSTERED.
>     Under current mdadm code logic, load_super1 will be called many
>     times, any new code in load_super1 will cost mdadm running more time.
>     And more reason is I prefer as much as possible to limit clustered
>     code spreading in every corner.
>
> So I used method <1> to fix this issue.
>
> How to trigger:
>
> dd if=/dev/zero bs=1M count=1 oflag=direct of=/dev/sda
> dd if=/dev/zero bs=1M count=1 oflag=direct of=/dev/sdb
> dd if=/dev/zero bs=1M count=1 oflag=direct of=/dev/sdc
> mdadm -C /dev/md0 -b clustered -e 1.2 -n 2 -l mirror /dev/sda /dev/sdb
> mdadm -a /dev/md0 /dev/sdc
> mdadm /dev/md0 --fail /dev/sda
> mdadm /dev/md0 --remove /dev/sda
> mdadm -Ss
> mdadm -A /dev/md0 /dev/sdb /dev/sdc
>
> the output of current "mdadm -X /dev/sdc":
> (there should be (by default) 4 slot info for correct output)
> ```
>          Filename : /dev/sdc
>             Magic : 6d746962
>           Version : 5
>              UUID : a74642f8:a6b1fba8:58e1f8db:cfe7b082
>            Events : 29
>    Events Cleared : 0
>             State : OK
>         Chunksize : 64 MB
>            Daemon : 5s flush period
>        Write Mode : Normal
>         Sync Size : 306176 (299.00 MiB 313.52 MB)
>            Bitmap : 5 bits (chunks), 5 dirty (100.0%)
> ```
>
> And mdadm later operations will trigger kernel output error message:
> (triggered by "mdadm -A /dev/md0 /dev/sdb /dev/sdc")
> ```
> kernel: md0: invalid bitmap file superblock: bad magic
> kernel: md_bitmap_copy_from_slot can't get bitmap from slot 1
> kernel: md-cluster: Could not gather bitmaps from slot 1
> kernel: md0: invalid bitmap file superblock: bad magic
> kernel: md_bitmap_copy_from_slot can't get bitmap from slot 2
> kernel: md-cluster: Could not gather bitmaps from slot 2
> kernel: md0: invalid bitmap file superblock: bad magic
> kernel: md_bitmap_copy_from_slot can't get bitmap from slot 3
> kernel: md-cluster: Could not gather bitmaps from slot 3
> kernel: md-cluster: failed to gather all resyn infos
> kernel: md0: detected capacity change from 0 to 612352
> ```
>
> Signed-off-by: Heming Zhao <heming.zhao@suse.com>

Acked-by: Coly Li <colyli@suse.de>


Thanks.


Coly Li


> ---
>   super1.c | 12 +++++++++++-
>   1 file changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/super1.c b/super1.c
> index a12a5bc847b9..f08d4f831319 100644
> --- a/super1.c
> +++ b/super1.c
> @@ -2674,7 +2674,17 @@ static int write_bitmap1(struct supertype *st, int fd, enum bitmap_update update
>   		}
>   
>   		if (bms->version == BITMAP_MAJOR_CLUSTERED) {
> -			if (__cpu_to_le32(st->nodes) < bms->nodes) {
> +			if (st->nodes == 1) {
> +				/* the parameter for nodes is not valid */
> +				pr_err("Warning: cluster-md at least needs two nodes\n");
> +				return -EINVAL;
> +			} else if (st->nodes == 0) {
> +				/*
> +				 * parameter "--nodes" is not specified, (eg, add a disk to
> +				 * clustered raid)
> +				 */
> +				break;
> +			} else if (__cpu_to_le32(st->nodes) < bms->nodes) {
>   				/*
>   				 * Since the nodes num is not increased, no
>   				 * need to check the space enough or not,