On 07/20/2012 07:41 PM, Sage Weil wrote:
> Previously, we were opportunistically initializing the bio_iter if it
> appeared to be uninitialized in the middle of the read path. The problem
> is that a sequence like:
>
> - start reading message
> - initialize bio_iter
> - read half a message
> - messenger fault, reconnect
> - restart reading message
> - ** bio_iter now non-NULL, not reinitialized **
> - read past end of bio, crash
>
> Instead, initialize the bio_iter unconditionally when we allocate/claim
> the message for read.
>
> Signed-off-by: Sage Weil <sage@xxxxxxxxxxx>
This seems to be similar to this recent change to the writing side
of things:
commit 43643528cce60ca184fe8197efa8e8da7c89a037
Author: Yan, Zheng <zheng.z.yan@xxxxxxxxx>
rbd: Clear ceph_msg->bio_iter for retransmitted message
In any case, this is the place where a new message is being
initialized, so it makes sense that this is where you re-init
the bio_iter pointer.
Reviewed-by: Alex Elder <elder@xxxxxxxxxxx>
> ---
> net/ceph/messenger.c | 11 ++++++-----
> 1 files changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
> index e24310e..efa369f 100644
> --- a/net/ceph/messenger.c
> +++ b/net/ceph/messenger.c
> @@ -1876,6 +1876,11 @@ static int read_partial_message(struct ceph_connection *con)
> else
> con->in_msg_pos.page_pos = 0;
> con->in_msg_pos.data_pos = 0;
> +
> +#ifdef CONFIG_BLOCK
> + if (m->bio)
> + init_bio_iter(m->bio, &m->bio_iter, &m->bio_seg);
> +#endif
> }
>
> /* front */
> @@ -1892,10 +1897,6 @@ static int read_partial_message(struct ceph_connection *con)
> if (ret <= 0)
> return ret;
> }
> -#ifdef CONFIG_BLOCK
> - if (m->bio && !m->bio_iter)
> - init_bio_iter(m->bio, &m->bio_iter, &m->bio_seg);
> -#endif
>
> /* (page) data */
> while (con->in_msg_pos.data_pos < data_len) {
> @@ -1906,7 +1907,7 @@ static int read_partial_message(struct ceph_connection *con)
> return ret;
> #ifdef CONFIG_BLOCK
> } else if (m->bio) {
> -
> + BUG_ON(!m->bio_iter);
> ret = read_partial_message_bio(con,
> &m->bio_iter, &m->bio_seg,
> data_len, do_datacrc);
>
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