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Subject[PATCH v2 md-6.11 07/12] md: don't fail action_store() if sync_thread is not registered
Date
From: Yu Kuai <yukuai3@huawei.com>

MD_RECOVERY_RUNNING will always be set when trying to register a new
sync_thread, however, if md_start_sync() turns out to do nothing,
MD_RECOVERY_RUNNING will be cleared in this case. And during the race
window, action_store() will return -EBUSY, which will cause some
mdadm tests to fail. For example:

The test 07reshape5intr will add a new disk to array, then start
reshape:

mdadm /dev/md0 --add /dev/xxx
mdadm --grow /dev/md0 -n 3

And add_bound_rdev() from mdadm --add will set MD_RECOVERY_NEEDED,
then during the race windown, mdadm --grow will fail.

Fix the problem by waiting in action_store() during the race window,
fail only if sync_thread is registered.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
---
drivers/md/md.c | 85 +++++++++++++++++++------------------------------
drivers/md/md.h | 2 --
2 files changed, 33 insertions(+), 54 deletions(-)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 44cb18ec1c52..86abd0fe0681 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -753,7 +753,6 @@ int mddev_init(struct mddev *mddev)

mutex_init(&mddev->open_mutex);
mutex_init(&mddev->reconfig_mutex);
- mutex_init(&mddev->sync_mutex);
mutex_init(&mddev->suspend_mutex);
mutex_init(&mddev->bitmap_info.mutex);
INIT_LIST_HEAD(&mddev->disks);
@@ -5021,34 +5020,6 @@ void md_unfrozen_sync_thread(struct mddev *mddev)
}
EXPORT_SYMBOL_GPL(md_unfrozen_sync_thread);

-static void idle_sync_thread(struct mddev *mddev)
-{
- mutex_lock(&mddev->sync_mutex);
- clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
-
- if (mddev_lock(mddev)) {
- mutex_unlock(&mddev->sync_mutex);
- return;
- }
-
- stop_sync_thread(mddev, false);
- mutex_unlock(&mddev->sync_mutex);
-}
-
-static void frozen_sync_thread(struct mddev *mddev)
-{
- mutex_lock(&mddev->sync_mutex);
- set_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
-
- if (mddev_lock(mddev)) {
- mutex_unlock(&mddev->sync_mutex);
- return;
- }
-
- stop_sync_thread(mddev, false);
- mutex_unlock(&mddev->sync_mutex);
-}
-
static int mddev_start_reshape(struct mddev *mddev)
{
int ret;
@@ -5056,24 +5027,13 @@ static int mddev_start_reshape(struct mddev *mddev)
if (mddev->pers->start_reshape == NULL)
return -EINVAL;

- ret = mddev_lock(mddev);
- if (ret)
- return ret;
-
- if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery)) {
- mddev_unlock(mddev);
- return -EBUSY;
- }
-
if (mddev->reshape_position == MaxSector ||
mddev->pers->check_reshape == NULL ||
mddev->pers->check_reshape(mddev)) {
clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
ret = mddev->pers->start_reshape(mddev);
- if (ret) {
- mddev_unlock(mddev);
+ if (ret)
return ret;
- }
} else {
/*
* If reshape is still in progress, and md_check_recovery() can
@@ -5083,7 +5043,6 @@ static int mddev_start_reshape(struct mddev *mddev)
clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
}

- mddev_unlock(mddev);
sysfs_notify_dirent_safe(mddev->sysfs_degraded);
return 0;
}
@@ -5097,36 +5056,53 @@ action_store(struct mddev *mddev, const char *page, size_t len)
if (!mddev->pers || !mddev->pers->sync_request)
return -EINVAL;

+retry:
+ if (work_busy(&mddev->sync_work))
+ flush_work(&mddev->sync_work);
+
+ ret = mddev_lock(mddev);
+ if (ret)
+ return ret;
+
+ if (work_busy(&mddev->sync_work)) {
+ mddev_unlock(mddev);
+ goto retry;
+ }
+
action = md_sync_action_by_name(page);

/* TODO: mdadm rely on "idle" to start sync_thread. */
if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery)) {
switch (action) {
case ACTION_FROZEN:
- frozen_sync_thread(mddev);
- return len;
+ md_frozen_sync_thread(mddev);
+ ret = len;
+ goto out;
case ACTION_IDLE:
- idle_sync_thread(mddev);
+ md_idle_sync_thread(mddev);
break;
case ACTION_RESHAPE:
case ACTION_RECOVER:
case ACTION_CHECK:
case ACTION_REPAIR:
case ACTION_RESYNC:
- return -EBUSY;
+ ret = -EBUSY;
+ goto out;
default:
- return -EINVAL;
+ ret = -EINVAL;
+ goto out;
}
} else {
switch (action) {
case ACTION_FROZEN:
set_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
- return len;
+ ret = len;
+ goto out;
case ACTION_RESHAPE:
clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
ret = mddev_start_reshape(mddev);
if (ret)
- return ret;
+ goto out;
break;
case ACTION_RECOVER:
clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
@@ -5144,7 +5120,8 @@ action_store(struct mddev *mddev, const char *page, size_t len)
clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
break;
default:
- return -EINVAL;
+ ret = -EINVAL;
+ goto out;
}
}

@@ -5152,14 +5129,18 @@ action_store(struct mddev *mddev, const char *page, size_t len)
/* A write to sync_action is enough to justify
* canceling read-auto mode
*/
- flush_work(&mddev->sync_work);
mddev->ro = MD_RDWR;
md_wakeup_thread(mddev->sync_thread);
}
+
set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
md_wakeup_thread(mddev->thread);
sysfs_notify_dirent_safe(mddev->sysfs_action);
- return len;
+ ret = len;
+
+out:
+ mddev_unlock(mddev);
+ return ret;
}

static struct md_sysfs_entry md_scan_mode =
diff --git a/drivers/md/md.h b/drivers/md/md.h
index 88add162b08e..732053b905b2 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -595,8 +595,6 @@ struct mddev {
*/
struct list_head deleting;

- /* Used to synchronize idle and frozen for action_store() */
- struct mutex sync_mutex;
/* The sequence number for sync thread */
atomic_t sync_seq;

--
2.39.2

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