Hi Xiubo!
xiubli@xxxxxxxxxx writes:
> From: Xiubo Li <xiubli@xxxxxxxxxx>
>
> A short read may occur while reading the message footer from the
> socket. Later, when the socket is ready for another read, the
> messenger shoudl invoke all read_partial* handlers, except the
> read_partial_sparse_msg_data(). The contract between the messenger
> and these handlers is that the handlers should bail if the area
> of the message is responsible for is already processed. So,
> in this case, it's expected that read_sparse_msg_data() would bail,
> allowing the messenger to invoke read_partial() for the footer and
> pick up where it left off.
>
> However read_partial_sparse_msg_data() violates that contract and
> ends up calling into the state machine in the OSD client. The
> sparse-read state machine just assumes that it's a new op and
> interprets some piece of the footer as the sparse-read extents/data
> and then returns bogus extents/data length, etc.
>
> This will just reuse the 'total_resid' to determine whether should
> the read_partial_sparse_msg_data() bail out or not. Because once
> it reaches to zero that means all the extents and data have been
> successfully received in last read, else it could break out when
> partially reading any of the extents and data. And then the
> osd_sparse_read() could continue where it left off.
I'm seeing an issue with fstest generic/580, which seems to enter an
infinite loop effectively rendering the testing VM unusable. It's pretty
easy to reproduce, just run the test ensuring to be using msgv2 (I'm
mounting the filesystem with 'ms_mode=crc'), and you should see the
following on the logs:
[...]
libceph: prepare_sparse_read_cont: ret 0x1000 total_resid 0x0 resid 0x0
libceph: osd1 (2)192.168.155.1:6810 read processing error
libceph: mon0 (2)192.168.155.1:40608 session established
libceph: bad late_status 0x1
libceph: osd1 (2)192.168.155.1:6810 protocol error, bad epilogue
libceph: mon0 (2)192.168.155.1:40608 session established
libceph: prepare_sparse_read_cont: ret 0x1000 total_resid 0x0 resid 0x0
libceph: osd1 (2)192.168.155.1:6810 read processing error
libceph: mon0 (2)192.168.155.1:40608 session established
libceph: bad late_status 0x1
[...]
Reverting this patch (commit 8e46a2d068c9 ("libceph: just wait for more
data to be available on the socket")) seems to fix. I haven't
investigated it further, but since it'll take me some time to refresh my
memory, I thought I should report it immediately. Maybe someone has any
idea.
Cheers,
--
Luís
> URL: https://tracker.ceph.com/issues/63586
> Signed-off-by: Xiubo Li <xiubli@xxxxxxxxxx>
> Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
> ---
> include/linux/ceph/messenger.h | 2 +-
> net/ceph/messenger_v1.c | 25 +++++++++++++------------
> net/ceph/messenger_v2.c | 4 ++--
> net/ceph/osd_client.c | 9 +++------
> 4 files changed, 19 insertions(+), 21 deletions(-)
>
> diff --git a/include/linux/ceph/messenger.h b/include/linux/ceph/messenger.h
> index 2eaaabbe98cb..1717cc57cdac 100644
> --- a/include/linux/ceph/messenger.h
> +++ b/include/linux/ceph/messenger.h
> @@ -283,7 +283,7 @@ struct ceph_msg {
> struct kref kref;
> bool more_to_follow;
> bool needs_out_seq;
> - bool sparse_read;
> + u64 sparse_read_total;
> int front_alloc_len;
>
> struct ceph_msgpool *pool;
> diff --git a/net/ceph/messenger_v1.c b/net/ceph/messenger_v1.c
> index 4cb60bacf5f5..126b2e712247 100644
> --- a/net/ceph/messenger_v1.c
> +++ b/net/ceph/messenger_v1.c
> @@ -160,8 +160,9 @@ static size_t sizeof_footer(struct ceph_connection *con)
> static void prepare_message_data(struct ceph_msg *msg, u32 data_len)
> {
> /* Initialize data cursor if it's not a sparse read */
> - if (!msg->sparse_read)
> - ceph_msg_data_cursor_init(&msg->cursor, msg, data_len);
> + u64 len = msg->sparse_read_total ? : data_len;
> +
> + ceph_msg_data_cursor_init(&msg->cursor, msg, len);
> }
>
> /*
> @@ -1036,7 +1037,7 @@ static int read_partial_sparse_msg_data(struct ceph_connection *con)
> if (do_datacrc)
> crc = con->in_data_crc;
>
> - do {
> + while (cursor->total_resid) {
> if (con->v1.in_sr_kvec.iov_base)
> ret = read_partial_message_chunk(con,
> &con->v1.in_sr_kvec,
> @@ -1044,23 +1045,23 @@ static int read_partial_sparse_msg_data(struct ceph_connection *con)
> &crc);
> else if (cursor->sr_resid > 0)
> ret = read_partial_sparse_msg_extent(con, &crc);
> -
> - if (ret <= 0) {
> - if (do_datacrc)
> - con->in_data_crc = crc;
> - return ret;
> - }
> + if (ret <= 0)
> + break;
>
> memset(&con->v1.in_sr_kvec, 0, sizeof(con->v1.in_sr_kvec));
> ret = con->ops->sparse_read(con, cursor,
> (char **)&con->v1.in_sr_kvec.iov_base);
> + if (ret <= 0) {
> + ret = ret ? ret : 1; /* must return > 0 to indicate success */
> + break;
> + }
> con->v1.in_sr_len = ret;
> - } while (ret > 0);
> + }
>
> if (do_datacrc)
> con->in_data_crc = crc;
>
> - return ret < 0 ? ret : 1; /* must return > 0 to indicate success */
> + return ret;
> }
>
> static int read_partial_msg_data(struct ceph_connection *con)
> @@ -1253,7 +1254,7 @@ static int read_partial_message(struct ceph_connection *con)
> if (!m->num_data_items)
> return -EIO;
>
> - if (m->sparse_read)
> + if (m->sparse_read_total)
> ret = read_partial_sparse_msg_data(con);
> else if (ceph_test_opt(from_msgr(con->msgr), RXBOUNCE))
> ret = read_partial_msg_data_bounce(con);
> diff --git a/net/ceph/messenger_v2.c b/net/ceph/messenger_v2.c
> index f8ec60e1aba3..a0ca5414b333 100644
> --- a/net/ceph/messenger_v2.c
> +++ b/net/ceph/messenger_v2.c
> @@ -1128,7 +1128,7 @@ static int decrypt_tail(struct ceph_connection *con)
> struct sg_table enc_sgt = {};
> struct sg_table sgt = {};
> struct page **pages = NULL;
> - bool sparse = con->in_msg->sparse_read;
> + bool sparse = !!con->in_msg->sparse_read_total;
> int dpos = 0;
> int tail_len;
> int ret;
> @@ -2060,7 +2060,7 @@ static int prepare_read_tail_plain(struct ceph_connection *con)
> }
>
> if (data_len(msg)) {
> - if (msg->sparse_read)
> + if (msg->sparse_read_total)
> con->v2.in_state = IN_S_PREPARE_SPARSE_DATA;
> else
> con->v2.in_state = IN_S_PREPARE_READ_DATA;
> diff --git a/net/ceph/osd_client.c b/net/ceph/osd_client.c
> index 837b69541376..ad2ed334cdbb 100644
> --- a/net/ceph/osd_client.c
> +++ b/net/ceph/osd_client.c
> @@ -5510,7 +5510,7 @@ static struct ceph_msg *get_reply(struct ceph_connection *con,
> }
>
> m = ceph_msg_get(req->r_reply);
> - m->sparse_read = (bool)srlen;
> + m->sparse_read_total = srlen;
>
> dout("get_reply tid %lld %p\n", tid, m);
>
> @@ -5777,11 +5777,8 @@ static int prep_next_sparse_read(struct ceph_connection *con,
> }
>
> if (o->o_sparse_op_idx < 0) {
> - u64 srlen = sparse_data_requested(req);
> -
> - dout("%s: [%d] starting new sparse read req. srlen=0x%llx\n",
> - __func__, o->o_osd, srlen);
> - ceph_msg_data_cursor_init(cursor, con->in_msg, srlen);
> + dout("%s: [%d] starting new sparse read req\n",
> + __func__, o->o_osd);
> } else {
> u64 end;
>
> --
>
> 2.43.0
>
