From 5792a2856a63cdc568e08a7d6f9b2413d9217b3e Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Wed, 4 Apr 2007 19:08:18 -0700 Subject: [PATCH] [PATCH] md: avoid a deadlock when removing a device from an md array via sysfs A device can be removed from an md array via e.g. echo remove > /sys/block/md3/md/dev-sde/state This will try to remove the 'dev-sde' subtree which will deadlock since commit e7b0d26a86943370c04d6833c6edba2a72a6e240 With this patch we run the kobject_del via schedule_work so as to avoid the deadlock. Cc: Alan Stern Signed-off-by: Neil Brown Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/md/md.c | 16 +++++++++++++++- include/linux/raid/md_k.h | 1 + 2 files changed, 16 insertions(+), 1 deletion(-) diff --git a/drivers/md/md.c b/drivers/md/md.c index 2a9b6a07e3a2..509171ca7fa8 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -1378,6 +1378,12 @@ static int bind_rdev_to_array(mdk_rdev_t * rdev, mddev_t * mddev) return err; } +static void delayed_delete(struct work_struct *ws) +{ + mdk_rdev_t *rdev = container_of(ws, mdk_rdev_t, del_work); + kobject_del(&rdev->kobj); +} + static void unbind_rdev_from_array(mdk_rdev_t * rdev) { char b[BDEVNAME_SIZE]; @@ -1390,7 +1396,12 @@ static void unbind_rdev_from_array(mdk_rdev_t * rdev) printk(KERN_INFO "md: unbind<%s>\n", bdevname(rdev->bdev,b)); rdev->mddev = NULL; sysfs_remove_link(&rdev->kobj, "block"); - kobject_del(&rdev->kobj); + + /* We need to delay this, otherwise we can deadlock when + * writing to 'remove' to "dev/state" + */ + INIT_WORK(&rdev->del_work, delayed_delete); + schedule_work(&rdev->del_work); } /* @@ -3389,6 +3400,9 @@ static int do_md_stop(mddev_t * mddev, int mode) sysfs_remove_link(&mddev->kobj, nm); } + /* make sure all delayed_delete calls have finished */ + flush_scheduled_work(); + export_array(mddev); mddev->array_size = 0; diff --git a/include/linux/raid/md_k.h b/include/linux/raid/md_k.h index 8245c282168b..de72c49747c8 100644 --- a/include/linux/raid/md_k.h +++ b/include/linux/raid/md_k.h @@ -104,6 +104,7 @@ struct mdk_rdev_s * for reporting to userspace and storing * in superblock. */ + struct work_struct del_work; /* used for delayed sysfs removal */ }; struct mddev_s -- 2.20.1