On 2/2/21 7:22 PM, Zhao Heming wrote:
> With kernel commit 480523feae58 ("md: only call set_in_sync() when it
> is expected to succeed."), mddev->in_sync in clustered array is always
> zero. It makes metadata resync_offset to always zero.
> When assembling a clusterd array with "-U no-bitmap" option, kernel
> md layer "mddev->resync_offset == 0" and "mddev->bitmap == NULL" will
> trigger raid1 do sync on every bitmap chunk. the sync action is useless,
> we should avoid it.
>
> Related kernel flow:
> ```
> md_do_sync
> mddev->pers->sync_request
> raid1_sync_request
> md_bitmap_start_sync(mddev->bitmap, sector_nr, &sync_blocks, 1)
> __bitmap_start_sync(bitmap, offset,&blocks1, degraded)
> if (bitmap == NULL) {/* FIXME or bitmap set as 'failed' */
> *blocks = 1024;
> return 1; /* always resync if no bitmap */
> }
> ```
>
> Reprodusible steps:
> ```
> node1 # mdadm -C /dev/md0 -b clustered -e 1.2 -n 2 -l mirror /dev/sd{a,b}
> node1 # mdadm -Ss
> (in another shell, executing & watching: watch -n 1 'cat /proc/mdstat')
> node1 # mdadm -A -U no-bitmap /dev/md0 /dev/sd{a,b}
> ```
>
> Signed-off-by: Zhao Heming <heming.zhao@xxxxxxxx>
> ---
> v2: only set MaxSector on bitmap clean device
Applied!
Thanks,
Jes
