• Dennis Yang's avatar
    md/raid5: preserve STRIPE_ON_UNPLUG_LIST in break_stripe_batch_list · 184a09eb
    Dennis Yang authored
    In release_stripe_plug(), if a stripe_head has its STRIPE_ON_UNPLUG_LIST
    set, it indicates that this stripe_head is already in the raid5_plug_cb
    list and release_stripe() would be called instead to drop a reference
    count. Otherwise, the STRIPE_ON_UNPLUG_LIST bit would be set for this
    stripe_head and it will get queued into the raid5_plug_cb list.
    
    Since break_stripe_batch_list() did not preserve STRIPE_ON_UNPLUG_LIST,
    A stripe could be re-added to plug list while it is still on that list
    in the following situation. If stripe_head A is added to another
    stripe_head B's batch list, in this case A will have its
    batch_head != NULL and be added into the plug list. After that,
    stripe_head B gets handled and called break_stripe_batch_list() to
    reset all the batched stripe_head(including A which is still on
    the plug list)'s state and reset their batch_head to NULL.
    Before the plug list gets processed, if there is another write request
    comes in and get stripe_head A, A will have its batch_head == NULL
    (cleared by calling break_stripe_batch_list() on B) and be added to
    plug list once again.
    Signed-off-by: default avatarDennis Yang <dennisyang@qnap.com>
    Cc: stable@vger.kernel.org (v4.1+)
    Signed-off-by: default avatarShaohua Li <shli@fb.com>
    184a09eb
raid5.c 238 KB