Hi, 在 2023/09/29 2:45, Song Liu 写道:
On Wed, Sep 27, 2023 at 11:22 PM Yu Kuai <yukuai1@xxxxxxxxxxxxxxx> wrote:From: Yu Kuai <yukuai3@xxxxxxxxxx> 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; - the new helpers is designed to be called before mddev_lock(), hence it support to be interrupted by user as well. Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx> --- drivers/md/md.c | 102 +++++++++++++++++++++++++++++++++++++++++++++++- drivers/md/md.h | 3 ++ 2 files changed, 103 insertions(+), 2 deletions(-) diff --git a/drivers/md/md.c b/drivers/md/md.c index e460b380143d..a075d03d03d3 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;Can we make mddev->suspended atomic_t, and use atomic_inc_return() here?
'suspend_mutex' is needed, because concurrent caller of mddev_suspend() shound be ordered, they need to wait for the first mddev_suspend() to be done. Updating suspended is protected by 'suspend_mutex' in the new api, so I think it's not necessary to use atomic, WRITE/READ_ONCE() should be enough. Thanks, Kuai
Thanks, Song [...] .
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