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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>
This commit is contained in:
NeilBrown 2012-12-11 13:35:54 +11:00
parent 1f3c9907b8
commit a7a3f08dc2
1 changed files with 6 additions and 0 deletions
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6
drivers/md/md.c
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@ -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