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scst: Confirm percpu refs has scheduled and switched to atomic

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This patch replaces percpu_ref_kill() with percpu_ref_kill_and_confirm()
to guarantee safe usage of references in atomic mode immediately
afterwards.

This change ensures accurate checking of active commands following the
initial reference killing.

Reported-by: Lev Vainblat <lev@zadarastorage.com>
This commit is contained in:
Gleb Chesnokov
2023-06-28 15:29:22 +03:00
parent bdf867ffd1
commit 6a925490fd
5 changed files with 40 additions and 15 deletions
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1
.github/workflows/checkpatch_pull.yml vendored
View File

@@ -30,6 +30,7 @@ jobs:
UNKNOWN_COMMIT_ID
NO_AUTHOR_SIGN_OFF
COMMIT_LOG_USE_LINK
BAD_REPORTED_BY_LINK
FILE_PATH_CHANGES
SPDX_LICENSE_TAG
LINUX_VERSION_CODE

1
.github/workflows/checkpatch_push.yml vendored
View File

@@ -35,6 +35,7 @@ jobs:
UNKNOWN_COMMIT_ID
NO_AUTHOR_SIGN_OFF
COMMIT_LOG_USE_LINK
BAD_REPORTED_BY_LINK
FILE_PATH_CHANGES
SPDX_LICENSE_TAG
LINUX_VERSION_CODE

10
scst/include/backport.h
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@@ -1098,13 +1098,21 @@ static inline void percpu_ref_put(struct percpu_ref *ref)
ref->release(ref);
}
static inline void percpu_ref_kill(struct percpu_ref *ref)
static inline void
percpu_ref_kill_and_confirm(struct percpu_ref *ref, percpu_ref_func_t *confirm_kill)
{
WARN_ON_ONCE(ref->dead);
ref->dead = true;
if (confirm_kill)
confirm_kill(ref);
percpu_ref_put(ref);
}
static inline void percpu_ref_kill(struct percpu_ref *ref)
{
percpu_ref_kill_and_confirm(ref, NULL);
}
static inline void percpu_ref_resurrect(struct percpu_ref *ref)
{
WARN_ON_ONCE(!ref->dead);

42
scst/src/scst_main.c
View File

@@ -129,7 +129,8 @@ spinlock_t scst_mgmt_lock;
struct list_head scst_sess_init_list;
struct list_head scst_sess_shut_list;
wait_queue_head_t scst_dev_cmd_waitQ;
static wait_queue_head_t scst_dev_cmd_waitQ;
static struct completion scst_confirm_done;
static struct mutex scst_cmd_threads_mutex;
/* protected by scst_cmd_threads_mutex */
@@ -792,7 +793,7 @@ static int scst_susp_wait(unsigned long timeout)
t = min(timeout, SCST_SUSP_WAIT_REPORT_TIMEOUT);
res = wait_event_interruptible_timeout(scst_dev_cmd_waitQ,
percpu_ref_killed, t);
percpu_ref_killed, t);
if (res > 0) {
res = 0;
goto out;
@@ -800,15 +801,16 @@ static int scst_susp_wait(unsigned long timeout)
goto out;
if (res == 0) {
PRINT_INFO("%d active commands to still not completed. See "
"README for possible reasons.", scst_get_cmd_counter());
PRINT_INFO(
"%d active commands to still not completed. See README for possible reasons.",
scst_get_cmd_counter());
scst_trace_cmds(scst_to_syslog, &hp);
scst_trace_mcmds(scst_to_syslog, &hp);
}
if (timeout != SCST_SUSPEND_TIMEOUT_UNLIMITED) {
res = wait_event_interruptible_timeout(scst_dev_cmd_waitQ,
percpu_ref_killed, timeout - t);
percpu_ref_killed, timeout - t);
if (res == 0)
res = -EBUSY;
else if (res > 0)
@@ -826,6 +828,11 @@ out:
#undef SCST_SUSP_WAIT_REPORT_TIMEOUT
}
static void scst_suspend_counter_confirm(struct percpu_ref *ref)
{
complete(&scst_confirm_done);
}
/*
* scst_suspend_activity() - globally suspend activity
*
@@ -864,8 +871,12 @@ int scst_suspend_activity(unsigned long timeout)
goto out_up;
/* Cause scst_get_cmd() to fail. */
init_completion(&scst_confirm_done);
percpu_ref_killed = false;
percpu_ref_kill(&scst_cmd_count);
percpu_ref_kill_and_confirm(&scst_cmd_count, scst_suspend_counter_confirm);
wait_for_completion(&scst_confirm_done);
/*
* See comment in scst_user.c::dev_user_task_mgmt_fn() for more
@@ -878,7 +889,7 @@ int scst_suspend_activity(unsigned long timeout)
if (scst_get_cmd_counter() != 0) {
PRINT_INFO("Waiting for %d active commands to complete...",
scst_get_cmd_counter());
scst_get_cmd_counter());
rep = true;
lock_contended(&scst_suspend_dep_map, _RET_IP_);
@@ -887,15 +898,19 @@ int scst_suspend_activity(unsigned long timeout)
res = scst_susp_wait(timeout);
/* Cause scst_get_mcmd() to fail. */
init_completion(&scst_confirm_done);
percpu_ref_killed = false;
percpu_ref_kill(&scst_mcmd_count);
percpu_ref_kill_and_confirm(&scst_mcmd_count, scst_suspend_counter_confirm);
wait_for_completion(&scst_confirm_done);
if (res != 0)
goto out_resume;
if (scst_get_cmd_counter() != 0)
TRACE_MGMT_DBG("Waiting for %d active commands finally to "
"complete", scst_get_cmd_counter());
TRACE_MGMT_DBG("Waiting for %d active commands finally to complete",
scst_get_cmd_counter());
if (timeout != SCST_SUSPEND_TIMEOUT_UNLIMITED) {
wait_time = jiffies - cur_time;
@@ -913,7 +928,7 @@ int scst_suspend_activity(unsigned long timeout)
goto out_resume;
if (rep)
PRINT_INFO("%s", "All active commands completed");
PRINT_INFO("All active commands completed");
out_up:
mutex_unlock(&scst_suspend_mutex);
@@ -973,8 +988,9 @@ static void __scst_resume_activity(void)
spin_lock_irq(&scst_mcmd_lock);
list_for_each_entry(m, &scst_delayed_mgmt_cmd_list,
mgmt_cmd_list_entry) {
TRACE_MGMT_DBG("Moving delayed mgmt cmd %p to head of active "
"mgmt cmd list", m);
TRACE_MGMT_DBG(
"Moving delayed mgmt cmd %p to head of active mgmt cmd list",
m);
}
list_splice_init(&scst_delayed_mgmt_cmd_list,
&scst_active_mgmt_cmd_list);

1
scst/src/scst_priv.h
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@@ -172,7 +172,6 @@ extern struct list_head scst_template_list;
extern struct list_head scst_dev_list;
extern struct list_head scst_dev_type_list;
extern struct list_head scst_virtual_dev_type_list;
extern wait_queue_head_t scst_dev_cmd_waitQ;
extern const struct scst_cl_ops scst_no_dlm_cl_ops;
extern const struct scst_cl_ops scst_dlm_cl_ops;