Re: [PATCH v3 4/5] libceph: add sparse read support to OSD client

[Xiubo Li <xiubli@redhat.com>]

On 3/18/22 9:50 PM, Jeff Layton wrote:
> Add a new sparse_read operation for the OSD client, driven by its own
> state machine. The messenger can repeatedly call the sparse_read
> operation, and it will pass back the necessary info to set up to read
> the next extent of data, while zero-filling the sparse regions.
>
> Signed-off-by: Jeff Layton <jlayton@kernel.org>
> ---
>   include/linux/ceph/osd_client.h |  32 +++++
>   net/ceph/osd_client.c           | 238 +++++++++++++++++++++++++++++++-
>   2 files changed, 266 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/ceph/osd_client.h b/include/linux/ceph/osd_client.h
> index 00a5b53a6763..2c5f9eb7d888 100644
> --- a/include/linux/ceph/osd_client.h
> +++ b/include/linux/ceph/osd_client.h
> @@ -40,6 +40,36 @@ struct ceph_sparse_extent {
>   	u64	len;
>   } __attribute__((packed));
>   
> +/* Sparse read state machine state values */
> +enum ceph_sparse_read_state {
> +	CEPH_SPARSE_READ_HDR	= 0,
> +	CEPH_SPARSE_READ_EXTENTS,
> +	CEPH_SPARSE_READ_DATA_LEN,
> +	CEPH_SPARSE_READ_DATA,
> +};
> +
> +/*
> + * A SPARSE_READ reply is a 32-bit count of extents, followed by an array of
> + * 64-bit offset/length pairs, and then all of the actual file data
> + * concatenated after it (sans holes).
> + *
> + * Unfortunately, we don't know how long the extent array is until we've
> + * started reading the data section of the reply. The caller should send down
> + * a destination buffer for the array, but we'll alloc one if it's too small
> + * or if the caller doesn't.
> + */
> +struct ceph_sparse_read {
> +	enum ceph_sparse_read_state	sr_state;	/* state machine state */
> +	u64				sr_req_off;	/* orig request offset */
> +	u64				sr_req_len;	/* orig request length */
> +	u64				sr_pos;		/* current pos in buffer */
> +	int				sr_index;	/* current extent index */
> +	__le32				sr_datalen;	/* length of actual data */
> +	u32				sr_count;	/* extent count in reply */
> +	int				sr_ext_len;	/* length of extent array */
> +	struct ceph_sparse_extent	*sr_extent;	/* extent array */
> +};
> +
>   /*
>    * A given osd we're communicating with.
>    *
> @@ -48,6 +78,7 @@ struct ceph_sparse_extent {
>    */
>   struct ceph_osd {
>   	refcount_t o_ref;
> +	int o_sparse_op_idx;
>   	struct ceph_osd_client *o_osdc;
>   	int o_osd;
>   	int o_incarnation;
> @@ -63,6 +94,7 @@ struct ceph_osd {
>   	unsigned long lru_ttl;
>   	struct list_head o_keepalive_item;
>   	struct mutex lock;
> +	struct ceph_sparse_read	o_sparse_read;
>   };
>   
>   #define CEPH_OSD_SLAB_OPS	2
> diff --git a/net/ceph/osd_client.c b/net/ceph/osd_client.c
> index 9fec258e1f8d..3694696c8a31 100644
> --- a/net/ceph/osd_client.c
> +++ b/net/ceph/osd_client.c
> @@ -376,6 +376,7 @@ static void osd_req_op_data_release(struct ceph_osd_request *osd_req,
>   
>   	switch (op->op) {
>   	case CEPH_OSD_OP_READ:
> +	case CEPH_OSD_OP_SPARSE_READ:
>   	case CEPH_OSD_OP_WRITE:
>   	case CEPH_OSD_OP_WRITEFULL:
>   		kfree(op->extent.sparse_ext);
> @@ -707,6 +708,7 @@ static void get_num_data_items(struct ceph_osd_request *req,
>   		/* reply */
>   		case CEPH_OSD_OP_STAT:
>   		case CEPH_OSD_OP_READ:
> +		case CEPH_OSD_OP_SPARSE_READ:
>   		case CEPH_OSD_OP_LIST_WATCHERS:
>   			*num_reply_data_items += 1;
>   			break;
> @@ -776,7 +778,7 @@ void osd_req_op_extent_init(struct ceph_osd_request *osd_req,
>   
>   	BUG_ON(opcode != CEPH_OSD_OP_READ && opcode != CEPH_OSD_OP_WRITE &&
>   	       opcode != CEPH_OSD_OP_WRITEFULL && opcode != CEPH_OSD_OP_ZERO &&
> -	       opcode != CEPH_OSD_OP_TRUNCATE);
> +	       opcode != CEPH_OSD_OP_TRUNCATE && opcode != CEPH_OSD_OP_SPARSE_READ);
>   
>   	op->extent.offset = offset;
>   	op->extent.length = length;
> @@ -985,6 +987,7 @@ static u32 osd_req_encode_op(struct ceph_osd_op *dst,
>   	case CEPH_OSD_OP_STAT:
>   		break;
>   	case CEPH_OSD_OP_READ:
> +	case CEPH_OSD_OP_SPARSE_READ:
>   	case CEPH_OSD_OP_WRITE:
>   	case CEPH_OSD_OP_WRITEFULL:
>   	case CEPH_OSD_OP_ZERO:
> @@ -1081,7 +1084,8 @@ struct ceph_osd_request *ceph_osdc_new_request(struct ceph_osd_client *osdc,
>   
>   	BUG_ON(opcode != CEPH_OSD_OP_READ && opcode != CEPH_OSD_OP_WRITE &&
>   	       opcode != CEPH_OSD_OP_ZERO && opcode != CEPH_OSD_OP_TRUNCATE &&
> -	       opcode != CEPH_OSD_OP_CREATE && opcode != CEPH_OSD_OP_DELETE);
> +	       opcode != CEPH_OSD_OP_CREATE && opcode != CEPH_OSD_OP_DELETE &&
> +	       opcode != CEPH_OSD_OP_SPARSE_READ);
>   
>   	req = ceph_osdc_alloc_request(osdc, snapc, num_ops, use_mempool,
>   					GFP_NOFS);
> @@ -1222,6 +1226,13 @@ static void osd_init(struct ceph_osd *osd)
>   	mutex_init(&osd->lock);
>   }
>   
> +static void ceph_init_sparse_read(struct ceph_sparse_read *sr)
> +{
> +	kfree(sr->sr_extent);
> +	memset(sr, '\0', sizeof(*sr));
> +	sr->sr_state = CEPH_SPARSE_READ_HDR;
> +}
> +
>   static void osd_cleanup(struct ceph_osd *osd)
>   {
>   	WARN_ON(!RB_EMPTY_NODE(&osd->o_node));
> @@ -1232,6 +1243,8 @@ static void osd_cleanup(struct ceph_osd *osd)
>   	WARN_ON(!list_empty(&osd->o_osd_lru));
>   	WARN_ON(!list_empty(&osd->o_keepalive_item));
>   
> +	ceph_init_sparse_read(&osd->o_sparse_read);
> +
>   	if (osd->o_auth.authorizer) {
>   		WARN_ON(osd_homeless(osd));
>   		ceph_auth_destroy_authorizer(osd->o_auth.authorizer);
> @@ -1251,6 +1264,9 @@ static struct ceph_osd *create_osd(struct ceph_osd_client *osdc, int onum)
>   	osd_init(osd);
>   	osd->o_osdc = osdc;
>   	osd->o_osd = onum;
> +	osd->o_sparse_op_idx = -1;
> +
> +	ceph_init_sparse_read(&osd->o_sparse_read);
>   
>   	ceph_con_init(&osd->o_con, osd, &osd_con_ops, &osdc->client->msgr);
>   
> @@ -2055,6 +2071,7 @@ static void setup_request_data(struct ceph_osd_request *req)
>   					       &op->raw_data_in);
>   			break;
>   		case CEPH_OSD_OP_READ:
> +		case CEPH_OSD_OP_SPARSE_READ:
>   			ceph_osdc_msg_data_add(reply_msg,
>   					       &op->extent.osd_data);
>   			break;
> @@ -2470,8 +2487,10 @@ static void finish_request(struct ceph_osd_request *req)
>   
>   	req->r_end_latency = ktime_get();
>   
> -	if (req->r_osd)
> +	if (req->r_osd) {
> +		ceph_init_sparse_read(&req->r_osd->o_sparse_read);
>   		unlink_request(req->r_osd, req);
> +	}
>   	atomic_dec(&osdc->num_requests);
>   
>   	/*
> @@ -5416,6 +5435,24 @@ static void osd_dispatch(struct ceph_connection *con, struct ceph_msg *msg)
>   	ceph_msg_put(msg);
>   }
>   
> +/* How much sparse data was requested? */
> +static u64 sparse_data_requested(struct ceph_osd_request *req)
> +{
> +	u64 len = 0;
> +
> +	if (req->r_flags & CEPH_OSD_FLAG_READ) {
> +		int i;
> +
> +		for (i = 0; i < req->r_num_ops; ++i) {
> +			struct ceph_osd_req_op *op = &req->r_ops[i];
> +
> +			if (op->op == CEPH_OSD_OP_SPARSE_READ)
> +				len += op->extent.length;
> +		}
> +	}
> +	return len;
> +}
> +
>   /*
>    * Lookup and return message for incoming reply.  Don't try to do
>    * anything about a larger than preallocated data portion of the
> @@ -5432,6 +5469,7 @@ static struct ceph_msg *get_reply(struct ceph_connection *con,
>   	int front_len = le32_to_cpu(hdr->front_len);
>   	int data_len = le32_to_cpu(hdr->data_len);
>   	u64 tid = le64_to_cpu(hdr->tid);
> +	u64 srlen;
>   
>   	down_read(&osdc->lock);
>   	if (!osd_registered(osd)) {
> @@ -5464,7 +5502,8 @@ static struct ceph_msg *get_reply(struct ceph_connection *con,
>   		req->r_reply = m;
>   	}
>   
> -	if (data_len > req->r_reply->data_length) {
> +	srlen = sparse_data_requested(req);
> +	if (!srlen && (data_len > req->r_reply->data_length)) {
>   		pr_warn("%s osd%d tid %llu data %d > preallocated %zu, skipping\n",
>   			__func__, osd->o_osd, req->r_tid, data_len,
>   			req->r_reply->data_length);
> @@ -5474,6 +5513,8 @@ static struct ceph_msg *get_reply(struct ceph_connection *con,
>   	}
>   
>   	m = ceph_msg_get(req->r_reply);
> +	m->sparse_read = (bool)srlen;
> +
>   	dout("get_reply tid %lld %p\n", tid, m);
>   
>   out_unlock_session:
> @@ -5706,9 +5747,198 @@ static int osd_check_message_signature(struct ceph_msg *msg)
>   	return ceph_auth_check_message_signature(auth, msg);
>   }
>   
> +static void advance_cursor(struct ceph_msg_data_cursor *cursor, size_t len, bool zero)
> +{
> +	while (len) {
> +		struct page *page;
> +		size_t poff, plen;
> +		bool last = false;
> +
> +		page = ceph_msg_data_next(cursor, &poff, &plen, &last);
> +		if (plen > len)
> +			plen = len;
> +		if (zero)
> +			zero_user_segment(page, poff, poff + plen);
> +		len -= plen;
> +		ceph_msg_data_advance(cursor, plen);
> +	}
> +}
> +
> +static int prep_next_sparse_read(struct ceph_connection *con,
> +				 struct ceph_msg_data_cursor *cursor)
> +{
> +	struct ceph_osd *o = con->private;
> +	struct ceph_sparse_read *sr = &o->o_sparse_read;
> +	struct ceph_osd_request *req;
> +	struct ceph_osd_req_op *op;
> +
> +	spin_lock(&o->o_requests_lock);
> +	req = lookup_request(&o->o_requests, le64_to_cpu(con->in_msg->hdr.tid));
> +	if (!req) {
> +		spin_unlock(&o->o_requests_lock);
> +		return -EBADR;
> +	}
> +
> +	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);
> +	} else {
> +		op = &req->r_ops[o->o_sparse_op_idx];
> +
> +		WARN_ON_ONCE(op->extent.sparse_ext);
> +
> +		/* hand back buffer we took earlier */
> +		op->extent.sparse_ext = sr->sr_extent;
> +		sr->sr_extent = NULL;
> +		op->extent.sparse_ext_len = sr->sr_count;
> +		sr->sr_ext_len = 0;
> +		dout("%s: [%d] completed extent array len %d cursor->resid %zd\n",
> +			__func__, o->o_osd, op->extent.sparse_ext_len,
> +			cursor->resid);
> +		/*
> +		 * FIXME: Need to advance to the next data item here, in the
> +		 * event that there are multiple sparse read requests. Is this
> +		 * the right way to do that?
> +		 */
> +		if (cursor->resid)
> +			advance_cursor(cursor, cursor->resid, false);
> +	}
> +
> +	ceph_init_sparse_read(sr);
> +
> +	/* find next op in this request (if any) */
> +	while (++o->o_sparse_op_idx < req->r_num_ops) {
> +		op = &req->r_ops[o->o_sparse_op_idx];
> +		if (op->op == CEPH_OSD_OP_SPARSE_READ)
> +			goto found;
> +	}
> +
> +	/* reset for next sparse read request */
> +	spin_unlock(&o->o_requests_lock);
> +	o->o_sparse_op_idx = -1;
> +	return 0;
> +found:
> +	sr->sr_req_off = op->extent.offset;
> +	sr->sr_req_len = op->extent.length;
> +	sr->sr_pos = sr->sr_req_off;
> +	dout("%s: [%d] new sparse read op at idx %d 0x%llx~0x%llx\n", __func__,
> +		o->o_osd, o->o_sparse_op_idx, sr->sr_req_off, sr->sr_req_len);
> +
> +	/* hand off request's sparse extent map buffer */
> +	sr->sr_ext_len = op->extent.sparse_ext_len;
> +	op->extent.sparse_ext_len = 0;
> +	sr->sr_extent = op->extent.sparse_ext;
> +	op->extent.sparse_ext = NULL;
> +
> +	spin_unlock(&o->o_requests_lock);
> +	return 1;
> +}
> +
> +#ifdef __BIG_ENDIAN
> +static inline void convert_extent_map(struct ceph_sparse_read *sr)
> +{
> +	int i;
> +
> +	for (i = 0; i < sr->sr_count; i++) {
> +		struct ceph_sparse_extent *ext = sr->sr_extent[i];
> +
> +		ext->off = le64_to_cpu((__force __le32)ext->off);
> +		ext->len = le64_to_cpu((__force __le32)ext->len);

Why '__le32' ? Shouldn't it be '__le64' ?

-- Xiubo


> +	}
> +}
> +#else
> +static inline void convert_extent_map(struct ceph_sparse_read *sr)
> +{
> +}
> +#endif
> +
> +static int osd_sparse_read(struct ceph_connection *con,
> +			   struct ceph_msg_data_cursor *cursor,
> +			   u64 *plen, char **pbuf)
> +{
> +	struct ceph_osd *o = con->private;
> +	struct ceph_sparse_read *sr = &o->o_sparse_read;
> +	u32 count = sr->sr_count;
> +	u64 eoff, elen;
> +	int ret;
> +
> +	switch (sr->sr_state) {
> +	case CEPH_SPARSE_READ_HDR:
> +next_op:
> +		ret = prep_next_sparse_read(con, cursor);
> +		if (ret <= 0)
> +			return ret;
> +
> +		/* number of extents */
> +		*plen = sizeof(sr->sr_count);
> +		*pbuf = (char *)&sr->sr_count;
> +		sr->sr_state = CEPH_SPARSE_READ_EXTENTS;
> +		break;
> +	case CEPH_SPARSE_READ_EXTENTS:
> +		/* Convert sr_count to host-endian */
> +		count = le32_to_cpu((__force __le32)sr->sr_count);
> +		sr->sr_count = count;
> +		dout("[%d] got %u extents\n", o->o_osd, count);
> +
> +		if (count > 0) {
> +			if (!sr->sr_extent || count > sr->sr_ext_len) {
> +				/* no extent array provided, or too short */
> +				kfree(sr->sr_extent);
> +				sr->sr_extent = kmalloc_array(count, sizeof(*sr->sr_extent),
> +							   GFP_NOIO);
> +				if (!sr->sr_extent)
> +					return -ENOMEM;
> +				sr->sr_ext_len = count;
> +			}
> +			*plen = count * sizeof(*sr->sr_extent);
> +			*pbuf = (char *)sr->sr_extent;
> +			sr->sr_state = CEPH_SPARSE_READ_DATA_LEN;
> +			break;
> +		}
> +		/* No extents? Fall through to reading data len */
> +		fallthrough;
> +	case CEPH_SPARSE_READ_DATA_LEN:
> +		convert_extent_map(sr);
> +		*plen = sizeof(sr->sr_datalen);
> +		*pbuf = (char *)&sr->sr_datalen;
> +		sr->sr_state = CEPH_SPARSE_READ_DATA;
> +		break;
> +	case CEPH_SPARSE_READ_DATA:
> +		if (sr->sr_index >= count) {
> +			sr->sr_state = CEPH_SPARSE_READ_HDR;
> +			goto next_op;
> +		}
> +
> +		eoff = sr->sr_extent[sr->sr_index].off;
> +		elen = sr->sr_extent[sr->sr_index].len;
> +
> +		dout("[%d] ext %d off 0x%llx len 0x%llx\n",
> +		     o->o_osd, sr->sr_index, eoff, elen);
> +
> +		/* zero out anything from sr_pos to start of extent */
> +		if (sr->sr_pos < eoff)
> +			advance_cursor(cursor, eoff - sr->sr_pos, true);
> +
> +		/* Set position to end of extent */
> +		sr->sr_pos = eoff + elen;
> +
> +		/* send back the new length */
> +		*plen = elen;
> +
> +		/* Bump the array index */
> +		++sr->sr_index;
> +		break;
> +	}
> +	return 1;
> +}
> +
>   static const struct ceph_connection_operations osd_con_ops = {
>   	.get = osd_get_con,
>   	.put = osd_put_con,
> +	.sparse_read = osd_sparse_read,
>   	.alloc_msg = osd_alloc_msg,
>   	.dispatch = osd_dispatch,
>   	.fault = osd_fault,