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scst: Use RCU read lock when accessing sess_tgt_dev_list #151

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merged 2 commits into from
Apr 17, 2023
Merged

scst: Use RCU read lock when accessing sess_tgt_dev_list #151

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8bd0f5f
scst: Use RCU read lock when accessing sess_tgt_dev_list
lnocturno Apr 17, 2023
b4bd27f
scst_lib: Avoid holding scst_mutex during sess_tgt_dev_list access
lnocturno Apr 17, 2023
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36 changes: 22 additions & 14 deletions scst/src/scst_lib.c
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Original file line number Diff line number Diff line change
Expand Up @@ -14084,11 +14084,11 @@ int scst_get_max_lun_commands(struct scst_session *sess, uint64_t lun)

TRACE_ENTRY();

mutex_lock(&scst_mutex);

if (sess == NULL) {
struct scst_device *dev;

mutex_lock(&scst_mutex);

list_for_each_entry(dev, &scst_dev_list, dev_list_entry) {
if (dev->handler == &scst_null_devtype)
continue;
Expand All @@ -14097,40 +14097,48 @@ int scst_get_max_lun_commands(struct scst_session *sess, uint64_t lun)
if (res > dev->max_tgt_dev_commands)
res = dev->max_tgt_dev_commands;
}
goto out_unlock;

mutex_unlock(&scst_mutex);

goto out;
}

if (lun != NO_SUCH_LUN) {
struct list_head *head =
&sess->sess_tgt_dev_list[SESS_TGT_DEV_LIST_HASH_FN(lun)];
struct list_head *head;
struct scst_tgt_dev *tgt_dev;

list_for_each_entry(tgt_dev, head, sess_tgt_dev_list_entry) {
rcu_read_lock();
head = &sess->sess_tgt_dev_list[SESS_TGT_DEV_LIST_HASH_FN(lun)];

list_for_each_entry_rcu(tgt_dev, head, sess_tgt_dev_list_entry) {
if (tgt_dev->lun == lun) {
res = tgt_dev->dev->max_tgt_dev_commands;
TRACE_DBG("tgt_dev %p, dev %s, max_tgt_dev_commands "
"%d (res %d)", tgt_dev, tgt_dev->dev->virt_name,
tgt_dev->dev->max_tgt_dev_commands, res);
TRACE_DBG("tgt_dev %p, dev %s, max_tgt_dev_commands %d (res %d)",
tgt_dev, tgt_dev->dev->virt_name,
tgt_dev->dev->max_tgt_dev_commands, res);
break;
}
}
goto out_unlock;
rcu_read_unlock();

goto out;
}

rcu_read_lock();
for (i = 0; i < SESS_TGT_DEV_LIST_HASH_SIZE; i++) {
struct list_head *head = &sess->sess_tgt_dev_list[i];
struct scst_tgt_dev *tgt_dev;

list_for_each_entry(tgt_dev, head, sess_tgt_dev_list_entry) {
list_for_each_entry_rcu(tgt_dev, head, sess_tgt_dev_list_entry) {
if (res > tgt_dev->dev->max_tgt_dev_commands)
res = tgt_dev->dev->max_tgt_dev_commands;
}
}
rcu_read_unlock();

out_unlock:
mutex_unlock(&scst_mutex);

out:
TRACE_EXIT_RES(res);

return res;
}
EXPORT_SYMBOL(scst_get_max_lun_commands);
Expand Down
4 changes: 3 additions & 1 deletion scst/src/scst_sysfs.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2557,11 +2557,12 @@ static ssize_t scst_tgt_forward_dst_store(struct kobject *kobj,
list_for_each_entry(sess, &tgt->sess_list, sess_list_entry) {
int i;

rcu_read_lock();
for (i = 0; i < SESS_TGT_DEV_LIST_HASH_SIZE; i++) {
struct list_head *head = &sess->sess_tgt_dev_list[i];
struct scst_tgt_dev *tgt_dev;

list_for_each_entry(tgt_dev, head, sess_tgt_dev_list_entry) {
list_for_each_entry_rcu(tgt_dev, head, sess_tgt_dev_list_entry) {
if (tgt->tgt_forward_dst)
set_bit(SCST_TGT_DEV_FORWARD_DST,
&tgt_dev->tgt_dev_flags);
Expand All @@ -2570,6 +2571,7 @@ static ssize_t scst_tgt_forward_dst_store(struct kobject *kobj,
&tgt_dev->tgt_dev_flags);
}
}
rcu_read_unlock();
}

if (tgt->tgt_forward_dst)
Expand Down
18 changes: 10 additions & 8 deletions scst/src/scst_targ.c
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Original file line number Diff line number Diff line change
Expand Up @@ -6153,7 +6153,6 @@ static int scst_abort_all_nexus_loss_sess(struct scst_mgmt_cmd *mcmd,
int res;
int i;
struct scst_session *sess = mcmd->sess;
struct scst_tgt_dev *tgt_dev;

TRACE_ENTRY();

Expand All @@ -6168,23 +6167,25 @@ static int scst_abort_all_nexus_loss_sess(struct scst_mgmt_cmd *mcmd,
rcu_read_lock();
for (i = 0; i < SESS_TGT_DEV_LIST_HASH_SIZE; i++) {
struct list_head *head = &sess->sess_tgt_dev_list[i];
struct scst_tgt_dev *tgt_dev;

list_for_each_entry_rcu(tgt_dev, head,
sess_tgt_dev_list_entry) {
__scst_abort_task_set(mcmd, tgt_dev);

scst_call_dev_task_mgmt_fn_received(mcmd, tgt_dev);

tm_dbg_task_mgmt(tgt_dev->dev, "NEXUS LOSS SESS or "
"ABORT ALL SESS or UNREG SESS",
tm_dbg_task_mgmt(tgt_dev->dev,
"NEXUS LOSS SESS or ABORT ALL SESS or UNREG SESS",
(mcmd->fn == SCST_UNREG_SESS_TM));
}
if (nexus_loss_unreg_sess) {
/*
* We need at first abort all affected commands and
* only then release them as part of clearing ACA
*/
list_for_each_entry(tgt_dev, head, sess_tgt_dev_list_entry) {
list_for_each_entry_rcu(tgt_dev, head,
sess_tgt_dev_list_entry) {
scst_clear_aca(tgt_dev,
(tgt_dev != mcmd->mcmd_tgt_dev));
}
Expand Down Expand Up @@ -6253,22 +6254,23 @@ static int scst_abort_all_nexus_loss_tgt(struct scst_mgmt_cmd *mcmd,
struct scst_tgt_dev *tgt_dev;

list_for_each_entry_rcu(tgt_dev, head,
sess_tgt_dev_list_entry) {
sess_tgt_dev_list_entry) {
__scst_abort_task_set(mcmd, tgt_dev);

if (mcmd->sess == tgt_dev->sess)
scst_call_dev_task_mgmt_fn_received(
mcmd, tgt_dev);

tm_dbg_task_mgmt(tgt_dev->dev, "NEXUS LOSS or "
"ABORT ALL", 0);
tm_dbg_task_mgmt(tgt_dev->dev,
"NEXUS LOSS or ABORT ALL", 0);
}
if (nexus_loss) {
/*
* We need at first abort all affected commands and
* only then release them as part of clearing ACA
*/
list_for_each_entry(tgt_dev, head, sess_tgt_dev_list_entry) {
list_for_each_entry_rcu(tgt_dev, head,
sess_tgt_dev_list_entry) {
scst_clear_aca(tgt_dev,
(tgt_dev != mcmd->mcmd_tgt_dev));
}
Expand Down