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

[Heming Zhao <heming.zhao@suse.com>]

Hello Jes,

ping...

I am not sure whether you are too busy to review my patch, or my mail
ate by anti-spam system.
This patch derived from a SUSE customer bug, it reverts incorrect code & make
cluster-md bitmap slot back to normal.

Thanks,
Heming 

On Tue, Apr 05, 2022 at 10:18:48PM +0800, 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
> ```
> 
> Acked-by: Coly Li <colyli@suse.de>
> Signed-off-by: Heming Zhao <heming.zhao@suse.com>
> ---
>  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,
> -- 
> 2.33.0
>