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Message-Id: <20230828020021.2489641-4-yukuai1@huaweicloud.com>
Date: Mon, 28 Aug 2023 09:59:56 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: agk@...hat.com, snitzer@...nel.org, dm-devel@...hat.com,
song@...nel.org, xni@...hat.com
Cc: linux-kernel@...r.kernel.org, linux-raid@...r.kernel.org,
yukuai3@...wei.com, yukuai1@...weicloud.com, yi.zhang@...wei.com,
yangerkun@...wei.com
Subject: [PATCH -next v2 03/28] md: add new helpers to suspend/resume array
From: Yu Kuai <yukuai3@...wei.com>
Advantages for new apis:
- reconfig_mutex is not required;
- the weird logical that suspend array hold 'reconfig_mutex' for
mddev_check_recovery() to update superblock is not needed;
- the specail handling, 'pers->prepare_suspend', for raid456 is not
needed;
- It's safe to be called at any time once mddev is allocated, and it's
designed to be used from slow path where array configuration is changed;
Signed-off-by: Yu Kuai <yukuai3@...wei.com>
---
drivers/md/md.c | 85 +++++++++++++++++++++++++++++++++++++++++++++++--
drivers/md/md.h | 3 ++
2 files changed, 86 insertions(+), 2 deletions(-)
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 7fa311a14317..6236e2e395c1 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -443,12 +443,22 @@ void mddev_suspend(struct mddev *mddev)
lockdep_is_held(&mddev->reconfig_mutex));
WARN_ON_ONCE(thread && current == thread->tsk);
- if (mddev->suspended++)
+
+ /* can't concurrent with __mddev_suspend() and __mddev_resume() */
+ mutex_lock(&mddev->suspend_mutex);
+ if (mddev->suspended++) {
+ mutex_unlock(&mddev->suspend_mutex);
return;
+ }
+
wake_up(&mddev->sb_wait);
set_bit(MD_ALLOW_SB_UPDATE, &mddev->flags);
percpu_ref_kill(&mddev->active_io);
+ /*
+ * TODO: cleanup 'pers->prepare_suspend after all callers are replaced
+ * by __mddev_suspend().
+ */
if (mddev->pers && mddev->pers->prepare_suspend)
mddev->pers->prepare_suspend(mddev);
@@ -459,14 +469,21 @@ void mddev_suspend(struct mddev *mddev)
del_timer_sync(&mddev->safemode_timer);
/* restrict memory reclaim I/O during raid array is suspend */
mddev->noio_flag = memalloc_noio_save();
+
+ mutex_unlock(&mddev->suspend_mutex);
}
EXPORT_SYMBOL_GPL(mddev_suspend);
void mddev_resume(struct mddev *mddev)
{
lockdep_assert_held(&mddev->reconfig_mutex);
- if (--mddev->suspended)
+
+ /* can't concurrent with __mddev_suspend() and __mddev_resume() */
+ mutex_lock(&mddev->suspend_mutex);
+ if (--mddev->suspended) {
+ mutex_unlock(&mddev->suspend_mutex);
return;
+ }
/* entred the memalloc scope from mddev_suspend() */
memalloc_noio_restore(mddev->noio_flag);
@@ -477,9 +494,72 @@ void mddev_resume(struct mddev *mddev)
set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
md_wakeup_thread(mddev->thread);
md_wakeup_thread(mddev->sync_thread); /* possibly kick off a reshape */
+
+ mutex_unlock(&mddev->suspend_mutex);
}
EXPORT_SYMBOL_GPL(mddev_resume);
+void __mddev_suspend(struct mddev *mddev)
+{
+
+ /*
+ * hold reconfig_mutex to wait for normal io will deadlock, because
+ * other context can't update super_block, and normal io can rely on
+ * updating super_block.
+ */
+ lockdep_assert_not_held(&mddev->reconfig_mutex);
+
+ mutex_lock(&mddev->suspend_mutex);
+
+ if (mddev->suspended) {
+ WRITE_ONCE(mddev->suspended, mddev->suspended + 1);
+ mutex_unlock(&mddev->suspend_mutex);
+ return;
+ }
+
+ percpu_ref_kill(&mddev->active_io);
+ wait_event(mddev->sb_wait, percpu_ref_is_zero(&mddev->active_io));
+
+ /*
+ * For raid456, io might be waiting for reshape to make progress,
+ * allow new reshape to start while waiting for io to be done to
+ * prevent deadlock.
+ */
+ WRITE_ONCE(mddev->suspended, mddev->suspended + 1);
+
+ del_timer_sync(&mddev->safemode_timer);
+ /* restrict memory reclaim I/O during raid array is suspend */
+ mddev->noio_flag = memalloc_noio_save();
+
+ mutex_unlock(&mddev->suspend_mutex);
+}
+EXPORT_SYMBOL_GPL(__mddev_suspend);
+
+void __mddev_resume(struct mddev *mddev)
+{
+ lockdep_assert_not_held(&mddev->reconfig_mutex);
+
+ mutex_lock(&mddev->suspend_mutex);
+ WRITE_ONCE(mddev->suspended, mddev->suspended - 1);
+ if (mddev->suspended) {
+ mutex_unlock(&mddev->suspend_mutex);
+ return;
+ }
+
+ /* entred the memalloc scope from __mddev_suspend() */
+ memalloc_noio_restore(mddev->noio_flag);
+
+ percpu_ref_resurrect(&mddev->active_io);
+ wake_up(&mddev->sb_wait);
+
+ set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
+ md_wakeup_thread(mddev->thread);
+ md_wakeup_thread(mddev->sync_thread); /* possibly kick off a reshape */
+
+ mutex_unlock(&mddev->suspend_mutex);
+}
+EXPORT_SYMBOL_GPL(__mddev_resume);
+
/*
* Generic flush handling for md
*/
@@ -667,6 +747,7 @@ 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);
INIT_LIST_HEAD(&mddev->all_mddevs);
diff --git a/drivers/md/md.h b/drivers/md/md.h
index fb3b123f16dd..1103e6b08ad9 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -316,6 +316,7 @@ struct mddev {
unsigned long sb_flags;
int suspended;
+ struct mutex suspend_mutex;
struct percpu_ref active_io;
int ro;
int sysfs_active; /* set when sysfs deletes
@@ -811,6 +812,8 @@ extern void md_rdev_clear(struct md_rdev *rdev);
extern void md_handle_request(struct mddev *mddev, struct bio *bio);
extern void mddev_suspend(struct mddev *mddev);
extern void mddev_resume(struct mddev *mddev);
+extern void __mddev_suspend(struct mddev *mddev);
+extern void __mddev_resume(struct mddev *mddev);
extern void md_reload_sb(struct mddev *mddev, int raid_disk);
extern void md_update_sb(struct mddev *mddev, int force);
--
2.39.2
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