• Mikulas Patocka's avatar
    dm thin: do not send discards to shared blocks · 650d2a06
    Mikulas Patocka authored
    When process_discard receives a partial discard that doesn't cover a
    full block, it sends this discard down to that block. Unfortunately, the
    block can be shared and the discard would corrupt the other snapshots
    sharing this block.
    
    This patch detects block sharing and ends the discard with success when
    sending it to the shared block.
    
    The above change means that if the device supports discard it can't be
    guaranteed that a discard request zeroes data. Therefore, we set
    ti->discard_zeroes_data_unsupported.
    
    Thin target discard support with this bug arrived in commit
    104655fd (dm thin: support discards).
    Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
    Cc: stable@kernel.org
    Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
    Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
    650d2a06
dm-thin.c 68.2 KB