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authorYu Kuai <yukuai3@huawei.com>2023-12-05 17:42:15 +0800
committerSong Liu <song@kernel.org>2023-12-06 12:44:00 -0800
commitf52f5c71f3d4bb0992800139d2f35cf9f6f6e0ee (patch)
tree518a172daaadb01e9d7882eba4dd12e4cc5486e3 /drivers/md
parentc9f7cb5b2bc968adcdc686c197ed108f47fd8eb0 (diff)
downloadlwn-f52f5c71f3d4bb0992800139d2f35cf9f6f6e0ee.tar.gz
lwn-f52f5c71f3d4bb0992800139d2f35cf9f6f6e0ee.zip
md: fix stopping sync thread
Currently sync thread is stopped from multiple contex: - idle_sync_thread - frozen_sync_thread - __md_stop_writes - md_set_readonly - do_md_stop And there are some problems: 1) sync_work is flushed while reconfig_mutex is grabbed, this can deadlock because the work function will grab reconfig_mutex as well. 2) md_reap_sync_thread() can't be called directly while md_do_sync() is not finished yet, for example, commit 130443d60b1b ("md: refactor idle/frozen_sync_thread() to fix deadlock"). 3) If MD_RECOVERY_RUNNING is not set, there is no need to stop sync_thread at all because sync_thread must not be registered. Factor out a helper stop_sync_thread(), so that above contex will behave the same. Fix 1) by flushing sync_work after reconfig_mutex is released, before waiting for sync_thread to be done; Fix 2) bt letting daemon thread to unregister sync_thread; Fix 3) by always checking MD_RECOVERY_RUNNING first. Fixes: db5e653d7c9f ("md: delay choosing sync action to md_start_sync()") Signed-off-by: Yu Kuai <yukuai3@huawei.com> Signed-off-by: Song Liu <song@kernel.org> Link: https://lore.kernel.org/r/20231205094215.1824240-4-yukuai1@huaweicloud.com
Diffstat (limited to 'drivers/md')
-rw-r--r--drivers/md/md.c90
1 files changed, 37 insertions, 53 deletions
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 2d8e45a1af23..bc9d67af1961 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -4840,25 +4840,29 @@ action_show(struct mddev *mddev, char *page)
return sprintf(page, "%s\n", type);
}
-static void stop_sync_thread(struct mddev *mddev)
+/**
+ * stop_sync_thread() - wait for sync_thread to stop if it's running.
+ * @mddev: the array.
+ * @locked: if set, reconfig_mutex will still be held after this function
+ * return; if not set, reconfig_mutex will be released after this
+ * function return.
+ * @check_seq: if set, only wait for curent running sync_thread to stop, noted
+ * that new sync_thread can still start.
+ */
+static void stop_sync_thread(struct mddev *mddev, bool locked, bool check_seq)
{
- if (!test_bit(MD_RECOVERY_RUNNING, &mddev->recovery))
- return;
+ int sync_seq;
- if (mddev_lock(mddev))
- return;
+ if (check_seq)
+ sync_seq = atomic_read(&mddev->sync_seq);
- /*
- * Check again in case MD_RECOVERY_RUNNING is cleared before lock is
- * held.
- */
if (!test_bit(MD_RECOVERY_RUNNING, &mddev->recovery)) {
- mddev_unlock(mddev);
+ if (!locked)
+ mddev_unlock(mddev);
return;
}
- if (work_pending(&mddev->sync_work))
- flush_workqueue(md_misc_wq);
+ mddev_unlock(mddev);
set_bit(MD_RECOVERY_INTR, &mddev->recovery);
/*
@@ -4866,21 +4870,28 @@ static void stop_sync_thread(struct mddev *mddev)
* never happen
*/
md_wakeup_thread_directly(mddev->sync_thread);
+ if (work_pending(&mddev->sync_work))
+ flush_work(&mddev->sync_work);
- mddev_unlock(mddev);
+ wait_event(resync_wait,
+ !test_bit(MD_RECOVERY_RUNNING, &mddev->recovery) ||
+ (check_seq && sync_seq != atomic_read(&mddev->sync_seq)));
+
+ if (locked)
+ mddev_lock_nointr(mddev);
}
static void idle_sync_thread(struct mddev *mddev)
{
- int sync_seq = atomic_read(&mddev->sync_seq);
-
mutex_lock(&mddev->sync_mutex);
clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
- stop_sync_thread(mddev);
- wait_event(resync_wait, sync_seq != atomic_read(&mddev->sync_seq) ||
- !test_bit(MD_RECOVERY_RUNNING, &mddev->recovery));
+ if (mddev_lock(mddev)) {
+ mutex_unlock(&mddev->sync_mutex);
+ return;
+ }
+ stop_sync_thread(mddev, false, true);
mutex_unlock(&mddev->sync_mutex);
}
@@ -4888,11 +4899,13 @@ static void frozen_sync_thread(struct mddev *mddev)
{
mutex_lock(&mddev->sync_mutex);
set_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
- stop_sync_thread(mddev);
- wait_event(resync_wait, mddev->sync_thread == NULL &&
- !test_bit(MD_RECOVERY_RUNNING, &mddev->recovery));
+ if (mddev_lock(mddev)) {
+ mutex_unlock(&mddev->sync_mutex);
+ return;
+ }
+ stop_sync_thread(mddev, false, false);
mutex_unlock(&mddev->sync_mutex);
}
@@ -6264,14 +6277,7 @@ static void md_clean(struct mddev *mddev)
static void __md_stop_writes(struct mddev *mddev)
{
- set_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
- if (work_pending(&mddev->sync_work))
- flush_workqueue(md_misc_wq);
- if (mddev->sync_thread) {
- set_bit(MD_RECOVERY_INTR, &mddev->recovery);
- md_reap_sync_thread(mddev);
- }
-
+ stop_sync_thread(mddev, true, false);
del_timer_sync(&mddev->safemode_timer);
if (mddev->pers && mddev->pers->quiesce) {
@@ -6363,18 +6369,8 @@ static int md_set_readonly(struct mddev *mddev, struct block_device *bdev)
set_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
md_wakeup_thread(mddev->thread);
}
- if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery))
- set_bit(MD_RECOVERY_INTR, &mddev->recovery);
-
- /*
- * Thread might be blocked waiting for metadata update which will now
- * never happen
- */
- md_wakeup_thread_directly(mddev->sync_thread);
- mddev_unlock(mddev);
- wait_event(resync_wait, !test_bit(MD_RECOVERY_RUNNING,
- &mddev->recovery));
+ stop_sync_thread(mddev, false, false);
wait_event(mddev->sb_wait,
!test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags));
mddev_lock_nointr(mddev);
@@ -6428,20 +6424,8 @@ static int do_md_stop(struct mddev *mddev, int mode,
set_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
md_wakeup_thread(mddev->thread);
}
- if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery))
- set_bit(MD_RECOVERY_INTR, &mddev->recovery);
- /*
- * Thread might be blocked waiting for metadata update which will now
- * never happen
- */
- md_wakeup_thread_directly(mddev->sync_thread);
-
- mddev_unlock(mddev);
- wait_event(resync_wait, (mddev->sync_thread == NULL &&
- !test_bit(MD_RECOVERY_RUNNING,
- &mddev->recovery)));
- mddev_lock_nointr(mddev);
+ stop_sync_thread(mddev, true, false);
mutex_lock(&mddev->open_mutex);
if ((mddev->pers && atomic_read(&mddev->openers) > !!bdev) ||