On Sunday July 17, mjt@xxxxxxxxxx wrote:
> When debugging some weird raid failure case, we come
> across a problem when kernel disallows assembling a
> linear array with zero chunksize, printing
> 'no chunksize specified' in dmesg and mdadm failing
> with EINVAL. The following patch fixes the problem
> (the patch is with large context to show why the change).
>
> Note chunk size is never used on linear array. The
> only usage of chunk_size member is in /proc/mdstat,
> as "rounding" parameter (linear.c) - looks like it
> should be removed too.
This statement isn't entirely true, though it took me a little while
to remind myself exactly how linear.c does use chunk_size.
linear_run in linear.c uses rdev->size for each devices.
in md.c rdev->size is set by a call to calc_dev_size()
calc_dev_size *does* use chunk_size (if it is non-zero)
However that doesn't make your patch wrong, as a zero chunk size
certainly seems to be handled correctly by linear. However I might
spend a little while reviewing that aspect of the code before I pass
on this patch.
Thanks,
NeilBrown
>
> Signed-Off-By: Michael Tokarev <mjt@xxxxxxxxxx>
>
> --- linux-2.6.12/drivers/md/md.c.orig 2005-06-17 23:48:29.000000000 +0400
> +++ linux-2.6.12/drivers/md/md.c 2005-07-17 03:07:05.000000000 +0400
> @@ -1516,21 +1516,21 @@ static int do_md_run(mddev_t * mddev)
>
> /*
> * Analyze all RAID superblock(s)
> */
> if (!mddev->raid_disks)
> analyze_sbs(mddev);
>
> chunk_size = mddev->chunk_size;
> pnum = level_to_pers(mddev->level);
>
> - if ((pnum != MULTIPATH) && (pnum != RAID1)) {
> + if ((pnum != MULTIPATH) && (pnum != RAID1) && (pnum != LINEAR)) {
> if (!chunk_size) {
> /*
> * 'default chunksize' in the old md code used to
> * be PAGE_SIZE, baaad.
> * we abort here to be on the safe side. We don't
> * want to continue the bad practice.
> */
> printk(KERN_ERR
> "no chunksize specified, see 'man raidtab'\n");
> return -EINVAL;
> -
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