• Mikulas Patocka's avatar
    dm: avoid unsupported spanning of md stripe boundaries · 8cbeb67a
    Mikulas Patocka authored
    A bio that has two or more vector entries, size less than or equal to
    page size, that crosses a stripe boundary of an underlying md device is
    accepted by device mapper (it conforms to all its limits) but not by the
    underlying device.
    
    The fix is: If device mapper selects the one-page maximum request size,
    it also needs to set its own q->merge_bvec_fn to reject any bios with
    multiple vector entries that span more pages.
    
    The problem was discovered in the following scenario:
      * MD - RAID-0
      * LV on the top of it (raid1, snapshot or striped with chunk
    size/stripe larger than RAID-0 stripe)
      * one of the logical volumes is exported to xen domU
      * inside xen domU it is partitioned, the key point is that the partition
    must be unaligned on page boundary (fdisk normally aligns the partition to
    63 sectors which will trigger it)
      * install the system on the partitioned disk in domU
    This causes I/O failures in dom0.
    Reference: https://bugzilla.redhat.com/show_bug.cgi?id=223947Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
    Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
    8cbeb67a
dm.c 37.7 KB