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

[Wen Gu <guwen@linux.alibaba.com>]

On 2024/3/21 16:12, Jan Karcher wrote:
> 
> 
> 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?
> 

rmb_node won't be unregistered until smc_lgr_free_bufs() in __smc_lgr_free(). At
that time, the connections on this lgr should be all freed (smc_conn_free() and
then lgr->refcnt == 0), so I think there will be no move data operation at that
point. But in case there is something unforeseen, I will put memcpy between dmb_ht_lock.

Thanks!

> 
>> +
>> +    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.
> 

OK, I will put it at the top. Thanks!

> 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