Hi, 在 2023/12/07 4:38, Song Liu 写道:
On Wed, Dec 6, 2023 at 12:37 AM Yuya Fujita <fujita.yuya-00@xxxxxxxxxxx> wrote:Do not unlock all_mddevs_lock in md_seq_show() and keep the lock until md_seq_stop(). The list of all_mddevs may be deleted in md_seq_show() because all_mddevs_lock is temporarily unlocked. The list should not be deleted while iterating over all_mddevs. (Just as the list should not be deleted during list_for_each_entry().) Fixes: cf1b6d4441ff ("md: simplify md_seq_ops") Signed-off-by: Yuya Fujita <fujita.yuya-00@xxxxxxxxxxx>Looks reasonable to me. Yu Kuai, what do you think about this?
I fail to understand what is the problem here if other mddev is deleted from the list while all_mddevs_lock is released during md_seq_show(), can you explain more? Thanks, Kuai
Thanks, Song--- drivers/md/md.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/drivers/md/md.c b/drivers/md/md.c index c94373d64f2c..97ef08608848 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -8293,7 +8293,6 @@ static int md_seq_show(struct seq_file *seq, void *v) if (!mddev_get(mddev)) return 0; - spin_unlock(&all_mddevs_lock); spin_lock(&mddev->lock); if (mddev->pers || mddev->raid_disks || !list_empty(&mddev->disks)) { seq_printf(seq, "%s : %sactive", mdname(mddev), @@ -8364,7 +8363,6 @@ static int md_seq_show(struct seq_file *seq, void *v) seq_printf(seq, "\n"); } spin_unlock(&mddev->lock); - spin_lock(&all_mddevs_lock); if (atomic_dec_and_test(&mddev->active)) __mddev_put(mddev); -- 2.31.1.
