Commit a7a3f08d authored Dec 11, 2012 by NeilBrown

md: close race between removing and adding a device.



When we remove a device from an md array, the final removal of
the "dev-XX" sys entry is run asynchronously.
If we then re-add that device immediately before the worker thread
gets to run, we can end up trying to add the "dev-XX" sysfs entry back
before it has been removed.

So in both places where we add a device, call
  flush_workqueue(md_misc_wq);
before taking the md lock (as holding the md lock can prevent removal
to complete).

Signed-off-by: NeilBrown <neilb@suse.de>

parent 1f3c9907

drivers/md/md.c

+6 −0

Original line number	Diff line number	Diff line
		@@ -4752,6 +4752,8 @@ md_attr_store(struct kobject kobj, struct attribute attr,
		}
		mddev_get(mddev);
		spin_unlock(&all_mddevs_lock);
		if (entry->store == new_dev_store)
		flush_workqueue(md_misc_wq);
		rv = mddev_lock(mddev);
		if (!rv) {
		rv = entry->store(mddev, page, length);
		@@ -6397,6 +6399,10 @@ static int md_ioctl(struct block_device *bdev, fmode_t mode,
		goto abort;
		}

		if (cmd == ADD_NEW_DISK)
		/* need to ensure md_delayed_delete() has completed */
		flush_workqueue(md_misc_wq);

		err = mddev_lock(mddev);
		if (err) {
		printk(KERN_INFO

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