[PATCH net-next 08/10] net/smc: replace mutex rmbs_lock and sndbufs_lock with rw_semaphore

D. Wythe
2022-08-10T17:48:29Z

From: "D. Wythe" <alibuda@linux.alibaba.com>

It's clear that rmbs_lock and sndbufs_lock are aims to protect the
rmbs list or the sndbufs list.

During conenction establieshment, smc_buf_get_slot() will always
be invoke, and it only performs read semantics in rmbs list and
sndbufs list.

Based on the above considerations, we replace mutex with rw_semaphore.
Only smc_buf_get_slot() use down_read() to allow smc_buf_get_slot()
run concurrently, other part use down_write() to keep exclusive
semantics.

Signed-off-by: D. Wythe <alibuda@linux.alibaba.com>
---
net/smc/smc_core.c | 55 +++++++++++++++++++++++++++---------------------------
net/smc/smc_core.h | 4 ++--
net/smc/smc_llc.c | 16 ++++++++--------
3 files changed, 38 insertions(+), 37 deletions(-)

diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c
index 113804d..b90970a 100644
--- a/net/smc/smc_core.c
+++ b/net/smc/smc_core.c
@@ -1138,8 +1138,8 @@ static int smc_lgr_create(struct smc_sock *smc, struct smc_init_info *ini)
lgr->freeing = 0;
lgr->vlan_id = ini->vlan_id;
refcount_set(&lgr->refcnt, 1); /* set lgr refcnt to 1 */
- mutex_init(&lgr->sndbufs_lock);
- mutex_init(&lgr->rmbs_lock);
+ init_rwsem(&lgr->sndbufs_lock);
+ init_rwsem(&lgr->rmbs_lock);
rwlock_init(&lgr->conns_lock);
for (i = 0; i < SMC_RMBE_SIZES; i++) {
INIT_LIST_HEAD(&lgr->sndbufs[i]);
@@ -1380,7 +1380,7 @@ struct smc_link *smc_switch_conns(struct smc_link_group *lgr,
static void smcr_buf_unuse(struct smc_buf_desc *buf_desc, bool is_rmb,
struct smc_link_group *lgr)
{
- struct mutex *lock; /* lock buffer list */
+ struct rw_semaphore *lock; /* lock buffer list */
int rc;

if (is_rmb && buf_desc->is_conf_rkey && !list_empty(&lgr->list)) {
@@ -1400,9 +1400,9 @@ static void smcr_buf_unuse(struct smc_buf_desc *buf_desc, bool is_rmb,
/* buf registration failed, reuse not possible */
lock = is_rmb ? &lgr->rmbs_lock :
&lgr->sndbufs_lock;
- mutex_lock(lock);
+ down_write(lock);
list_del(&buf_desc->list);
- mutex_unlock(lock);
+ up_write(lock);

smc_buf_free(lgr, is_rmb, buf_desc);
} else {
@@ -1506,15 +1506,16 @@ static void smcr_buf_unmap_lgr(struct smc_link *lnk)
int i;

for (i = 0; i < SMC_RMBE_SIZES; i++) {
- mutex_lock(&lgr->rmbs_lock);
+ down_write(&lgr->rmbs_lock);
list_for_each_entry_safe(buf_desc, bf, &lgr->rmbs[i], list)
smcr_buf_unmap_link(buf_desc, true, lnk);
- mutex_unlock(&lgr->rmbs_lock);
- mutex_lock(&lgr->sndbufs_lock);
+ up_write(&lgr->rmbs_lock);
+
+ down_write(&lgr->sndbufs_lock);
list_for_each_entry_safe(buf_desc, bf, &lgr->sndbufs[i],
list)
smcr_buf_unmap_link(buf_desc, false, lnk);
- mutex_unlock(&lgr->sndbufs_lock);
+ up_write(&lgr->sndbufs_lock);
}
}

@@ -2324,19 +2325,19 @@ int smc_uncompress_bufsize(u8 compressed)
* buffer size; if not available, return NULL
*/
static struct smc_buf_desc *smc_buf_get_slot(int compressed_bufsize,
- struct mutex *lock,
+ struct rw_semaphore *lock,
struct list_head *buf_list)
{
struct smc_buf_desc *buf_slot;

- mutex_lock(lock);
+ down_read(lock);
list_for_each_entry(buf_slot, buf_list, list) {
if (cmpxchg(&buf_slot->used, 0, 1) == 0) {
- mutex_unlock(lock);
+ up_read(lock);
return buf_slot;
}
}
- mutex_unlock(lock);
+ up_read(lock);
return NULL;
}

@@ -2445,13 +2446,13 @@ int smcr_link_reg_buf(struct smc_link *link, struct smc_buf_desc *buf_desc)
return 0;
}

-static int _smcr_buf_map_lgr(struct smc_link *lnk, struct mutex *lock,
+static int _smcr_buf_map_lgr(struct smc_link *lnk, struct rw_semaphore *lock,
struct list_head *lst, bool is_rmb)
{
struct smc_buf_desc *buf_desc, *bf;
int rc = 0;

- mutex_lock(lock);
+ down_write(lock);
list_for_each_entry_safe(buf_desc, bf, lst, list) {
if (!buf_desc->used)
continue;
@@ -2460,7 +2461,7 @@ static int _smcr_buf_map_lgr(struct smc_link *lnk, struct mutex *lock,
goto out;
}
out:
- mutex_unlock(lock);
+ up_write(lock);
return rc;
}

@@ -2493,37 +2494,37 @@ int smcr_buf_reg_lgr(struct smc_link *lnk)
int i, rc = 0;

/* reg all RMBs for a new link */
- mutex_lock(&lgr->rmbs_lock);
+ down_write(&lgr->rmbs_lock);
for (i = 0; i < SMC_RMBE_SIZES; i++) {
list_for_each_entry_safe(buf_desc, bf, &lgr->rmbs[i], list) {
if (!buf_desc->used)
continue;
rc = smcr_link_reg_buf(lnk, buf_desc);
if (rc) {
- mutex_unlock(&lgr->rmbs_lock);
+ up_write(&lgr->rmbs_lock);
return rc;
}
}
}
- mutex_unlock(&lgr->rmbs_lock);
+ up_write(&lgr->rmbs_lock);

if (lgr->buf_type == SMCR_PHYS_CONT_BUFS)
return rc;

/* reg all vzalloced sndbufs for a new link */
- mutex_lock(&lgr->sndbufs_lock);
+ down_write(&lgr->sndbufs_lock);
for (i = 0; i < SMC_RMBE_SIZES; i++) {
list_for_each_entry_safe(buf_desc, bf, &lgr->sndbufs[i], list) {
if (!buf_desc->used || !buf_desc->is_vm)
continue;
rc = smcr_link_reg_buf(lnk, buf_desc);
if (rc) {
- mutex_unlock(&lgr->sndbufs_lock);
+ up_write(&lgr->sndbufs_lock);
return rc;
}
}
}
- mutex_unlock(&lgr->sndbufs_lock);
+ up_write(&lgr->sndbufs_lock);
return rc;
}

@@ -2641,7 +2642,7 @@ static int __smc_buf_create(struct smc_sock *smc, bool is_smcd, bool is_rmb)
struct list_head *buf_list;
int bufsize, bufsize_short;
bool is_dgraded = false;
- struct mutex *lock; /* lock buffer list */
+ struct rw_semaphore *lock; /* lock buffer list */
int sk_buf_size;

if (is_rmb)
@@ -2689,9 +2690,9 @@ static int __smc_buf_create(struct smc_sock *smc, bool is_smcd, bool is_rmb)
SMC_STAT_RMB_ALLOC(smc, is_smcd, is_rmb);
SMC_STAT_RMB_SIZE(smc, is_smcd, is_rmb, bufsize);
buf_desc->used = 1;
- mutex_lock(lock);
+ down_write(lock);
list_add(&buf_desc->list, buf_list);
- mutex_unlock(lock);
+ up_write(lock);
break; /* found */
}

@@ -2765,9 +2766,9 @@ int smc_buf_create(struct smc_sock *smc, bool is_smcd)
/* create rmb */
rc = __smc_buf_create(smc, is_smcd, true);
if (rc) {
- mutex_lock(&smc->conn.lgr->sndbufs_lock);
+ down_write(&smc->conn.lgr->sndbufs_lock);
list_del(&smc->conn.sndbuf_desc->list);
- mutex_unlock(&smc->conn.lgr->sndbufs_lock);
+ up_write(&smc->conn.lgr->sndbufs_lock);
smc_buf_free(smc->conn.lgr, false, smc->conn.sndbuf_desc);
smc->conn.sndbuf_desc = NULL;
}
diff --git a/net/smc/smc_core.h b/net/smc/smc_core.h
index 559d330..008148c 100644
--- a/net/smc/smc_core.h
+++ b/net/smc/smc_core.h
@@ -300,9 +300,9 @@ struct smc_link_group {
unsigned short vlan_id; /* vlan id of link group */

struct list_head sndbufs[SMC_RMBE_SIZES];/* tx buffers */
- struct mutex sndbufs_lock; /* protects tx buffers */
+ struct rw_semaphore sndbufs_lock; /* protects tx buffers */
struct list_head rmbs[SMC_RMBE_SIZES]; /* rx buffers */
- struct mutex rmbs_lock; /* protects rx buffers */
+ struct rw_semaphore rmbs_lock; /* protects rx buffers */

u8 id[SMC_LGR_ID_SIZE]; /* unique lgr id */
struct delayed_work free_work; /* delayed freeing of an lgr */
diff --git a/net/smc/smc_llc.c b/net/smc/smc_llc.c
index d744937..76f9906 100644
--- a/net/smc/smc_llc.c
+++ b/net/smc/smc_llc.c
@@ -642,7 +642,7 @@ static int smc_llc_fill_ext_v2(struct smc_llc_msg_add_link_v2_ext *ext,

prim_lnk_idx = link->link_idx;
lnk_idx = link_new->link_idx;
- mutex_lock(&lgr->rmbs_lock);
+ down_write(&lgr->rmbs_lock);
ext->num_rkeys = lgr->conns_num;
if (!ext->num_rkeys)
goto out;
@@ -662,7 +662,7 @@ static int smc_llc_fill_ext_v2(struct smc_llc_msg_add_link_v2_ext *ext,
}
len += i * sizeof(ext->rt[0]);
out:
- mutex_unlock(&lgr->rmbs_lock);
+ up_write(&lgr->rmbs_lock);
return len;
}

@@ -923,7 +923,7 @@ static int smc_llc_cli_rkey_exchange(struct smc_link *link,
int rc = 0;
int i;

- mutex_lock(&lgr->rmbs_lock);
+ down_write(&lgr->rmbs_lock);
num_rkeys_send = lgr->conns_num;
buf_pos = smc_llc_get_first_rmb(lgr, &buf_lst);
do {
@@ -950,7 +950,7 @@ static int smc_llc_cli_rkey_exchange(struct smc_link *link,
break;
} while (num_rkeys_send || num_rkeys_recv);

- mutex_unlock(&lgr->rmbs_lock);
+ up_write(&lgr->rmbs_lock);
return rc;
}

@@ -1033,14 +1033,14 @@ static void smc_llc_save_add_link_rkeys(struct smc_link *link,
ext = (struct smc_llc_msg_add_link_v2_ext *)((u8 *)lgr->wr_rx_buf_v2 +
SMC_WR_TX_SIZE);
max = min_t(u8, ext->num_rkeys, SMC_LLC_RKEYS_PER_MSG_V2);
- mutex_lock(&lgr->rmbs_lock);
+ down_write(&lgr->rmbs_lock);
for (i = 0; i < max; i++) {
smc_rtoken_set(lgr, link->link_idx, link_new->link_idx,
ext->rt[i].rmb_key,
ext->rt[i].rmb_vaddr_new,
ext->rt[i].rmb_key_new);
}
- mutex_unlock(&lgr->rmbs_lock);
+ up_write(&lgr->rmbs_lock);
}

static void smc_llc_save_add_link_info(struct smc_link *link,
@@ -1349,7 +1349,7 @@ static int smc_llc_srv_rkey_exchange(struct smc_link *link,
int rc = 0;
int i;

- mutex_lock(&lgr->rmbs_lock);
+ down_write(&lgr->rmbs_lock);
num_rkeys_send = lgr->conns_num;
buf_pos = smc_llc_get_first_rmb(lgr, &buf_lst);
do {
@@ -1374,7 +1374,7 @@ static int smc_llc_srv_rkey_exchange(struct smc_link *link,
smc_llc_flow_qentry_del(&lgr->llc_flow_lcl);
} while (num_rkeys_send || num_rkeys_recv);
out:
- mutex_unlock(&lgr->rmbs_lock);
+ up_write(&lgr->rmbs_lock);
return rc;
}

--
1.8.3.1