On Thu, 12 Feb 2015, Mikulas Patocka wrote:
> It may be possible that a device claims discard support but it rejects
> discards with -EOPNOTSUPP. It happens when using loopback on ext2/ext3
> filesystem driven by the ext4 driver. It may also happen if the underlying
> devices are moved from one disk on another.
>
> If discard error happens, we reject the bio with -EOPNOTSUPP, but we do
> not degrade the array.
>
> This patch fixes failed test shell/lvconvert-repair-transient.sh in the
> lvm2 testsuite if the testsuite is extracted on an ext2 or ext3 filesystem
> and it is being driven by the ext4 driver.
>
> Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
I forgot to add
Cc: stable@xxxxxxxxxx
BTW. that ext4 behavior is specific to RHEL 7. On upstream kernel, the
ext4 driver can punch a hole in the ext2 or ext3 filesystem, but there are
corruptions when doing it - see bug 1176840.
Mikulas
> Index: linux-2.6/drivers/md/dm-raid1.c
> ===================================================================
> --- linux-2.6.orig/drivers/md/dm-raid1.c
> +++ linux-2.6/drivers/md/dm-raid1.c
> @@ -604,6 +604,15 @@ static void write_callback(unsigned long
> return;
> }
>
> + /*
> + * If the bio is discard, return an error, but do not
> + * degrade the array.
> + */
> + if (bio->bi_rw & REQ_DISCARD) {
> + bio_endio(bio, -EOPNOTSUPP);
> + return;
> + }
> +
> for (i = 0; i < ms->nr_mirrors; i++)
> if (test_bit(i, &error))
> fail_mirror(ms->mirror + i, DM_RAID1_WRITE_ERROR);
>
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