Re: [RFC PATCH net-next v4 05/11] net/smc: implement DMB-related operations of loopback-ism

[Jan Karcher <jaka@linux.ibm.com>]

On 17/03/2024 11:05, Wen Gu wrote:
> This implements DMB (un)registration and data move operations of
> loopback-ism device.
> 
> Signed-off-by: Wen Gu <guwen@linux.alibaba.com>
> ---
>   net/smc/smc_loopback.c | 131 ++++++++++++++++++++++++++++++++++++++++-
>   net/smc/smc_loopback.h |  13 ++++
>   2 files changed, 141 insertions(+), 3 deletions(-)
> 
> diff --git a/net/smc/smc_loopback.c b/net/smc/smc_loopback.c
> index 253128c77208..7335acb03920 100644
> --- a/net/smc/smc_loopback.c
> +++ b/net/smc/smc_loopback.c
> @@ -15,11 +15,13 @@
>   #include <linux/types.h>
>   #include <net/smc.h>
>   
> +#include "smc_cdc.h"
>   #include "smc_ism.h"
>   #include "smc_loopback.h"
>   
>   #if IS_ENABLED(CONFIG_SMC_LO)
>   #define SMC_LO_V2_CAPABLE	0x1 /* loopback-ism acts as ISMv2 */
> +#define SMC_DMA_ADDR_INVALID	(~(dma_addr_t)0)
>   
>   static const char smc_lo_dev_name[] = "loopback-ism";
>   static struct smc_lo_dev *lo_dev;
> @@ -49,6 +51,93 @@ static int smc_lo_query_rgid(struct smcd_dev *smcd, struct smcd_gid *rgid,
>   	return 0;
>   }
>   
> +static int smc_lo_register_dmb(struct smcd_dev *smcd, struct smcd_dmb *dmb,
> +			       void *client_priv)
> +{
> +	struct smc_lo_dmb_node *dmb_node, *tmp_node;
> +	struct smc_lo_dev *ldev = smcd->priv;
> +	int sba_idx, rc;
> +
> +	/* check space for new dmb */
> +	for_each_clear_bit(sba_idx, ldev->sba_idx_mask, SMC_LO_MAX_DMBS) {
> +		if (!test_and_set_bit(sba_idx, ldev->sba_idx_mask))
> +			break;
> +	}
> +	if (sba_idx == SMC_LO_MAX_DMBS)
> +		return -ENOSPC;
> +
> +	dmb_node = kzalloc(sizeof(*dmb_node), GFP_KERNEL);
> +	if (!dmb_node) {
> +		rc = -ENOMEM;
> +		goto err_bit;
> +	}
> +
> +	dmb_node->sba_idx = sba_idx;
> +	dmb_node->len = dmb->dmb_len;
> +	dmb_node->cpu_addr = kzalloc(dmb_node->len, GFP_KERNEL |
> +				     __GFP_NOWARN | __GFP_NORETRY |
> +				     __GFP_NOMEMALLOC);
> +	if (!dmb_node->cpu_addr) {
> +		rc = -ENOMEM;
> +		goto err_node;
> +	}
> +	dmb_node->dma_addr = SMC_DMA_ADDR_INVALID;
> +
> +again:
> +	/* add new dmb into hash table */
> +	get_random_bytes(&dmb_node->token, sizeof(dmb_node->token));
> +	write_lock_bh(&ldev->dmb_ht_lock);
> +	hash_for_each_possible(ldev->dmb_ht, tmp_node, list, dmb_node->token) {
> +		if (tmp_node->token == dmb_node->token) {
> +			write_unlock_bh(&ldev->dmb_ht_lock);
> +			goto again;
> +		}
> +	}
> +	hash_add(ldev->dmb_ht, &dmb_node->list, dmb_node->token);
> +	write_unlock_bh(&ldev->dmb_ht_lock);
> +
> +	dmb->sba_idx = dmb_node->sba_idx;
> +	dmb->dmb_tok = dmb_node->token;
> +	dmb->cpu_addr = dmb_node->cpu_addr;
> +	dmb->dma_addr = dmb_node->dma_addr;
> +	dmb->dmb_len = dmb_node->len;
> +
> +	return 0;
> +
> +err_node:
> +	kfree(dmb_node);
> +err_bit:
> +	clear_bit(sba_idx, ldev->sba_idx_mask);
> +	return rc;
> +}
> +
> +static int smc_lo_unregister_dmb(struct smcd_dev *smcd, struct smcd_dmb *dmb)
> +{
> +	struct smc_lo_dmb_node *dmb_node = NULL, *tmp_node;
> +	struct smc_lo_dev *ldev = smcd->priv;
> +
> +	/* remove dmb from hash table */
> +	write_lock_bh(&ldev->dmb_ht_lock);
> +	hash_for_each_possible(ldev->dmb_ht, tmp_node, list, dmb->dmb_tok) {
> +		if (tmp_node->token == dmb->dmb_tok) {
> +			dmb_node = tmp_node;
> +			break;
> +		}
> +	}
> +	if (!dmb_node) {
> +		write_unlock_bh(&ldev->dmb_ht_lock);
> +		return -EINVAL;
> +	}
> +	hash_del(&dmb_node->list);
> +	write_unlock_bh(&ldev->dmb_ht_lock);
> +
> +	clear_bit(dmb_node->sba_idx, ldev->sba_idx_mask);
> +	kfree(dmb_node->cpu_addr);
> +	kfree(dmb_node);
> +
> +	return 0;
> +}
> +
>   static int smc_lo_add_vlan_id(struct smcd_dev *smcd, u64 vlan_id)
>   {
>   	return -EOPNOTSUPP;
> @@ -75,6 +164,40 @@ static int smc_lo_signal_event(struct smcd_dev *dev, struct smcd_gid *rgid,
>   	return 0;
>   }
>   
> +static int smc_lo_move_data(struct smcd_dev *smcd, u64 dmb_tok,
> +			    unsigned int idx, bool sf, unsigned int offset,
> +			    void *data, unsigned int size)
> +{
> +	struct smc_lo_dmb_node *rmb_node = NULL, *tmp_node;
> +	struct smc_lo_dev *ldev = smcd->priv;
> +
> +	read_lock_bh(&ldev->dmb_ht_lock);
> +	hash_for_each_possible(ldev->dmb_ht, tmp_node, list, dmb_tok) {
> +		if (tmp_node->token == dmb_tok) {
> +			rmb_node = tmp_node;
> +			break;
> +		}
> +	}
> +	if (!rmb_node) {
> +		read_unlock_bh(&ldev->dmb_ht_lock);
> +		return -EINVAL;
> +	}
> +	read_unlock_bh(&ldev->dmb_ht_lock);
> +
> +	memcpy((char *)rmb_node->cpu_addr + offset, data, size);

Hi Wen Gu,

Could we get into use after free trouble here if the dmb gets 
unregistered between the read_unlock and memcpy?


> +
> +	if (sf) {
> +		struct smc_connection *conn =
> +			smcd->conn[rmb_node->sba_idx];

Please put the `struct smc_connection *conn = NULL` at the top of the 
function and assign the value here.

Thanks
- Jan

> +
> +		if (conn && !conn->killed)
> +			tasklet_schedule(&conn->rx_tsklet);
> +		else
> +			return -EPIPE;
> +	}
> +	return 0;
> +}
> +
>   static int smc_lo_supports_v2(void)
>   {
>   	return SMC_LO_V2_CAPABLE;
> @@ -101,14 +224,14 @@ static struct device *smc_lo_get_dev(struct smcd_dev *smcd)
>   
>   static const struct smcd_ops lo_ops = {
>   	.query_remote_gid = smc_lo_query_rgid,
> -	.register_dmb		= NULL,
> -	.unregister_dmb		= NULL,
> +	.register_dmb = smc_lo_register_dmb,
> +	.unregister_dmb = smc_lo_unregister_dmb,
>   	.add_vlan_id = smc_lo_add_vlan_id,
>   	.del_vlan_id = smc_lo_del_vlan_id,
>   	.set_vlan_required = smc_lo_set_vlan_required,
>   	.reset_vlan_required = smc_lo_reset_vlan_required,
>   	.signal_event = smc_lo_signal_event,
> -	.move_data		= NULL,
> +	.move_data = smc_lo_move_data,
>   	.supports_v2 = smc_lo_supports_v2,
>   	.get_local_gid = smc_lo_get_local_gid,
>   	.get_chid = smc_lo_get_chid,
> @@ -173,6 +296,8 @@ static void smcd_lo_unregister_dev(struct smc_lo_dev *ldev)
>   static int smc_lo_dev_init(struct smc_lo_dev *ldev)
>   {
>   	smc_lo_generate_id(ldev);
> +	rwlock_init(&ldev->dmb_ht_lock);
> +	hash_init(ldev->dmb_ht);
>   	return smcd_lo_register_dev(ldev);
>   }
>   
> diff --git a/net/smc/smc_loopback.h b/net/smc/smc_loopback.h
> index 55b41133a97f..24ab9d747613 100644
> --- a/net/smc/smc_loopback.h
> +++ b/net/smc/smc_loopback.h
> @@ -20,13 +20,26 @@
>   
>   #if IS_ENABLED(CONFIG_SMC_LO)
>   #define SMC_LO_MAX_DMBS		5000
> +#define SMC_LO_DMBS_HASH_BITS	12
>   #define SMC_LO_CHID		0xFFFF
>   
> +struct smc_lo_dmb_node {
> +	struct hlist_node list;
> +	u64 token;
> +	u32 len;
> +	u32 sba_idx;
> +	void *cpu_addr;
> +	dma_addr_t dma_addr;
> +};
> +
>   struct smc_lo_dev {
>   	struct smcd_dev *smcd;
>   	struct device dev;
>   	u16 chid;
>   	struct smcd_gid local_gid;
> +	rwlock_t dmb_ht_lock;
> +	DECLARE_BITMAP(sba_idx_mask, SMC_LO_MAX_DMBS);
> +	DECLARE_HASHTABLE(dmb_ht, SMC_LO_DMBS_HASH_BITS);
>   };
>   #endif
>