[PATCH v13 03/59] libceph: add sparse read support to msgr2 crc state machine

Jeff Layton
2022-04-05T20:28:14Z

Add support for a new sparse_read ceph_connection operation. The idea is
that the client driver can define this operation use it to do special
handling for incoming reads.

The alloc_msg routine will look at the request and determine whether the
reply is expected to be sparse. If it is, then we'll dispatch to a
different set of state machine states that will repeatedly call the
driver's sparse_read op to get length and placement info for reading the
extent map, and the extents themselves.

This necessitates adding some new field to some other structs:

- The msg gets a new bool to track whether it's a sparse_read request.

- A new field is added to the cursor to track the amount remaining in the
current extent. This is used to cap the read from the socket into the
msg_data

- Handing a revoke with all of this is particularly difficult, so I've
added a new data_len_remain field to the v2 connection info, and then
use that to skip that much on a revoke. We may want to expand the use of
that to the normal read path as well, just for consistency's sake.

Reviewed-by: Xiubo Li <xiubli@redhat.com>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
include/linux/ceph/messenger.h | 28 ++++++
net/ceph/messenger.c | 1 +
net/ceph/messenger_v2.c | 168 +++++++++++++++++++++++++++++++--
3 files changed, 188 insertions(+), 9 deletions(-)

diff --git a/include/linux/ceph/messenger.h b/include/linux/ceph/messenger.h
index e7f2fb2fc207..7f09a4213834 100644
--- a/include/linux/ceph/messenger.h
+++ b/include/linux/ceph/messenger.h
@@ -17,6 +17,7 @@

struct ceph_msg;
struct ceph_connection;
+struct ceph_msg_data_cursor;

/*
* Ceph defines these callbacks for handling connection events.
@@ -70,6 +71,30 @@ struct ceph_connection_operations {
int used_proto, int result,
const int *allowed_protos, int proto_cnt,
const int *allowed_modes, int mode_cnt);
+
+ /**
+ * sparse_read: read sparse data
+ * @con: connection we're reading from
+ * @cursor: data cursor for reading extents
+ * @buf: optional buffer to read into
+ *
+ * This should be called more than once, each time setting up to
+ * receive an extent into the current cursor position, and zeroing
+ * the holes between them.
+ *
+ * Returns amount of data to be read (in bytes), 0 if reading is
+ * complete, or -errno if there was an error.
+ *
+ * If @buf is set on a >0 return, then the data should be read into
+ * the provided buffer. Otherwise, it should be read into the cursor.
+ *
+ * The sparse read operation is expected to initialize the cursor
+ * with a length covering up to the end of the last extent.
+ */
+ int (*sparse_read)(struct ceph_connection *con,
+ struct ceph_msg_data_cursor *cursor,
+ char **buf);
+
};

/* use format string %s%lld */
@@ -207,6 +232,7 @@ struct ceph_msg_data_cursor {

struct ceph_msg_data *data; /* current data item */
size_t resid; /* bytes not yet consumed */
+ int sr_resid; /* residual sparse_read len */
bool last_piece; /* current is last piece */
bool need_crc; /* crc update needed */
union {
@@ -252,6 +278,7 @@ struct ceph_msg {
struct kref kref;
bool more_to_follow;
bool needs_out_seq;
+ bool sparse_read;
int front_alloc_len;

struct ceph_msgpool *pool;
@@ -396,6 +423,7 @@ struct ceph_connection_v2_info {

void *conn_bufs[16];
int conn_buf_cnt;
+ int data_len_remain;

struct kvec in_sign_kvecs[8];
struct kvec out_sign_kvecs[8];
diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index d3bb656308b4..bf4e7f5751ee 100644
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -1034,6 +1034,7 @@ void ceph_msg_data_cursor_init(struct ceph_msg_data_cursor *cursor,

cursor->total_resid = length;
cursor->data = msg->data;
+ cursor->sr_resid = 0;

__ceph_msg_data_cursor_init(cursor);
}
diff --git a/net/ceph/messenger_v2.c b/net/ceph/messenger_v2.c
index c6e5bfc717d5..d527777af584 100644
--- a/net/ceph/messenger_v2.c
+++ b/net/ceph/messenger_v2.c
@@ -52,14 +52,16 @@
#define FRAME_LATE_STATUS_COMPLETE 0xe
#define FRAME_LATE_STATUS_ABORTED_MASK 0xf

-#define IN_S_HANDLE_PREAMBLE 1
-#define IN_S_HANDLE_CONTROL 2
-#define IN_S_HANDLE_CONTROL_REMAINDER 3
-#define IN_S_PREPARE_READ_DATA 4
-#define IN_S_PREPARE_READ_DATA_CONT 5
-#define IN_S_PREPARE_READ_ENC_PAGE 6
-#define IN_S_HANDLE_EPILOGUE 7
-#define IN_S_FINISH_SKIP 8
+#define IN_S_HANDLE_PREAMBLE 1
+#define IN_S_HANDLE_CONTROL 2
+#define IN_S_HANDLE_CONTROL_REMAINDER 3
+#define IN_S_PREPARE_READ_DATA 4
+#define IN_S_PREPARE_READ_DATA_CONT 5
+#define IN_S_PREPARE_READ_ENC_PAGE 6
+#define IN_S_PREPARE_SPARSE_DATA 7
+#define IN_S_PREPARE_SPARSE_DATA_CONT 8
+#define IN_S_HANDLE_EPILOGUE 9
+#define IN_S_FINISH_SKIP 10

#define OUT_S_QUEUE_DATA 1
#define OUT_S_QUEUE_DATA_CONT 2
@@ -1819,6 +1821,124 @@ static void prepare_read_data_cont(struct ceph_connection *con)
con->v2.in_state = IN_S_HANDLE_EPILOGUE;
}

+static int prepare_sparse_read_cont(struct ceph_connection *con)
+{
+ int ret;
+ struct bio_vec bv;
+ char *buf = NULL;
+ struct ceph_msg_data_cursor *cursor = &con->v2.in_cursor;
+
+ WARN_ON(con->v2.in_state != IN_S_PREPARE_SPARSE_DATA_CONT);
+
+ if (iov_iter_is_bvec(&con->v2.in_iter)) {
+ if (ceph_test_opt(from_msgr(con->msgr), RXBOUNCE)) {
+ con->in_data_crc = crc32c(con->in_data_crc,
+ page_address(con->bounce_page),
+ con->v2.in_bvec.bv_len);
+ get_bvec_at(cursor, &bv);
+ memcpy_to_page(bv.bv_page, bv.bv_offset,
+ page_address(con->bounce_page),
+ con->v2.in_bvec.bv_len);
+ } else {
+ con->in_data_crc = ceph_crc32c_page(con->in_data_crc,
+ con->v2.in_bvec.bv_page,
+ con->v2.in_bvec.bv_offset,
+ con->v2.in_bvec.bv_len);
+ }
+
+ ceph_msg_data_advance(cursor, con->v2.in_bvec.bv_len);
+ cursor->sr_resid -= con->v2.in_bvec.bv_len;
+ dout("%s: advance by 0x%x sr_resid 0x%x\n", __func__,
+ con->v2.in_bvec.bv_len, cursor->sr_resid);
+ WARN_ON_ONCE(cursor->sr_resid > cursor->total_resid);
+ if (cursor->sr_resid) {
+ get_bvec_at(cursor, &bv);
+ if (bv.bv_len > cursor->sr_resid)
+ bv.bv_len = cursor->sr_resid;
+ if (ceph_test_opt(from_msgr(con->msgr), RXBOUNCE)) {
+ bv.bv_page = con->bounce_page;
+ bv.bv_offset = 0;
+ }
+ set_in_bvec(con, &bv);
+ con->v2.data_len_remain -= bv.bv_len;
+ return 0;
+ }
+ } else if (iov_iter_is_kvec(&con->v2.in_iter)) {
+ /* On first call, we have no kvec so don't compute crc */
+ if (con->v2.in_kvec_cnt) {
+ WARN_ON_ONCE(con->v2.in_kvec_cnt > 1);
+ con->in_data_crc = crc32c(con->in_data_crc,
+ con->v2.in_kvecs[0].iov_base,
+ con->v2.in_kvecs[0].iov_len);
+ }
+ } else {
+ return -EIO;
+ }
+
+ /* get next extent */
+ ret = con->ops->sparse_read(con, cursor, &buf);
+ if (ret <= 0) {
+ if (ret < 0)
+ return ret;
+
+ reset_in_kvecs(con);
+ add_in_kvec(con, con->v2.in_buf, CEPH_EPILOGUE_PLAIN_LEN);
+ con->v2.in_state = IN_S_HANDLE_EPILOGUE;
+ return 0;
+ }
+
+ if (buf) {
+ /* receive into buffer */
+ reset_in_kvecs(con);
+ add_in_kvec(con, buf, ret);
+ con->v2.data_len_remain -= ret;
+ return 0;
+ }
+
+ if (ret > cursor->total_resid) {
+ pr_warn("%s: ret 0x%x total_resid 0x%zx resid 0x%zx last %d\n",
+ __func__, ret, cursor->total_resid, cursor->resid,
+ cursor->last_piece);
+ return -EIO;
+ }
+ get_bvec_at(cursor, &bv);
+ if (bv.bv_len > cursor->sr_resid)
+ bv.bv_len = cursor->sr_resid;
+ if (ceph_test_opt(from_msgr(con->msgr), RXBOUNCE)) {
+ if (unlikely(!con->bounce_page)) {
+ con->bounce_page = alloc_page(GFP_NOIO);
+ if (!con->bounce_page) {
+ pr_err("failed to allocate bounce page\n");
+ return -ENOMEM;
+ }
+ }
+
+ bv.bv_page = con->bounce_page;
+ bv.bv_offset = 0;
+ }
+ set_in_bvec(con, &bv);
+ con->v2.data_len_remain -= ret;
+ return ret;
+}
+
+static int prepare_sparse_read_data(struct ceph_connection *con)
+{
+ struct ceph_msg *msg = con->in_msg;
+
+ dout("%s: starting sparse read\n", __func__);
+
+ if (WARN_ON_ONCE(!con->ops->sparse_read))
+ return -EOPNOTSUPP;
+
+ if (!con_secure(con))
+ con->in_data_crc = -1;
+
+ reset_in_kvecs(con);
+ con->v2.in_state = IN_S_PREPARE_SPARSE_DATA_CONT;
+ con->v2.data_len_remain = data_len(msg);
+ return prepare_sparse_read_cont(con);
+}
+
static int prepare_read_tail_plain(struct ceph_connection *con)
{
struct ceph_msg *msg = con->in_msg;
@@ -1839,7 +1959,10 @@ static int prepare_read_tail_plain(struct ceph_connection *con)
}

if (data_len(msg)) {
- con->v2.in_state = IN_S_PREPARE_READ_DATA;
+ if (msg->sparse_read)
+ con->v2.in_state = IN_S_PREPARE_SPARSE_DATA;
+ else
+ con->v2.in_state = IN_S_PREPARE_READ_DATA;
} else {
add_in_kvec(con, con->v2.in_buf, CEPH_EPILOGUE_PLAIN_LEN);
con->v2.in_state = IN_S_HANDLE_EPILOGUE;
@@ -2893,6 +3016,12 @@ static int populate_in_iter(struct ceph_connection *con)
prepare_read_enc_page(con);
ret = 0;
break;
+ case IN_S_PREPARE_SPARSE_DATA:
+ ret = prepare_sparse_read_data(con);
+ break;
+ case IN_S_PREPARE_SPARSE_DATA_CONT:
+ ret = prepare_sparse_read_cont(con);
+ break;
case IN_S_HANDLE_EPILOGUE:
ret = handle_epilogue(con);
break;
@@ -3485,6 +3614,23 @@ static void revoke_at_prepare_read_enc_page(struct ceph_connection *con)
con->v2.in_state = IN_S_FINISH_SKIP;
}

+static void revoke_at_prepare_sparse_data(struct ceph_connection *con)
+{
+ int resid; /* current piece of data */
+ int remaining;
+
+ WARN_ON(con_secure(con));
+ WARN_ON(!data_len(con->in_msg));
+ WARN_ON(!iov_iter_is_bvec(&con->v2.in_iter));
+ resid = iov_iter_count(&con->v2.in_iter);
+ dout("%s con %p resid %d\n", __func__, con, resid);
+
+ remaining = CEPH_EPILOGUE_PLAIN_LEN + con->v2.data_len_remain;
+ con->v2.in_iter.count -= resid;
+ set_in_skip(con, resid + remaining);
+ con->v2.in_state = IN_S_FINISH_SKIP;
+}
+
static void revoke_at_handle_epilogue(struct ceph_connection *con)
{
int resid;
@@ -3501,6 +3647,7 @@ static void revoke_at_handle_epilogue(struct ceph_connection *con)
void ceph_con_v2_revoke_incoming(struct ceph_connection *con)
{
switch (con->v2.in_state) {
+ case IN_S_PREPARE_SPARSE_DATA:
case IN_S_PREPARE_READ_DATA:
revoke_at_prepare_read_data(con);
break;
@@ -3510,6 +3657,9 @@ void ceph_con_v2_revoke_incoming(struct ceph_connection *con)
case IN_S_PREPARE_READ_ENC_PAGE:
revoke_at_prepare_read_enc_page(con);
break;
+ case IN_S_PREPARE_SPARSE_DATA_CONT:
+ revoke_at_prepare_sparse_data(con);
+ break;
case IN_S_HANDLE_EPILOGUE:
revoke_at_handle_epilogue(con);
break;
--
2.35.1