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>
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 89dbd44..8b0e3d2 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -4752,6 +4752,8 @@
}
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 @@
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