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Commit 7343dd61 authored by Justin Maggard's avatar Justin Maggard Committed by Filipe Manana
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btrfs: qgroup: exit the rescan worker during umount 



I was hitting a consistent NULL pointer dereference during shutdown that
showed the trace running through end_workqueue_bio().  I traced it back to
the endio_meta_workers workqueue being poked after it had already been
destroyed.

Eventually I found that the root cause was a qgroup rescan that was still
in progress while we were stopping all the btrfs workers.

Currently we explicitly pause balance and scrub operations in
close_ctree(), but we do nothing to stop the qgroup rescan.  We should
probably be doing the same for qgroup rescan, but that's a much larger
change.  This small change is good enough to allow me to unmount without
crashing.

Signed-off-by: default avatarJustin Maggard <jmaggard@netgear.com>
Reviewed-by: default avatarFilipe Manana <fdmanana@suse.com>
parent 9c9464cc

fs/btrfs/disk-io.c

+3 −0
Original line number Diff line number Diff line
@@ -3780,6 +3780,9 @@ void close_ctree(struct btrfs_root *root) 
	fs_info->closing = 1;

	smp_mb();



	/* wait for the qgroup rescan worker to stop */

	btrfs_qgroup_wait_for_completion(fs_info);



	/* wait for the uuid_scan task to finish */

	down(&fs_info->uuid_tree_rescan_sem);

	/* avoid complains from lockdep et al., set sem back to initial state */

fs/btrfs/qgroup.c

+6 −3
Original line number Diff line number Diff line
@@ -2286,7 +2286,7 @@ static void btrfs_qgroup_rescan_worker(struct btrfs_work *work) 
		goto out;



	err = 0;

	while (!err) {

	while (!err && !btrfs_fs_closing(fs_info)) {

		trans = btrfs_start_transaction(fs_info->fs_root, 0);

		if (IS_ERR(trans)) {

			err = PTR_ERR(trans);
@@ -2307,6 +2307,7 @@ static void btrfs_qgroup_rescan_worker(struct btrfs_work *work) 
	btrfs_free_path(path);



	mutex_lock(&fs_info->qgroup_rescan_lock);

	if (!btrfs_fs_closing(fs_info))

		fs_info->qgroup_flags &= ~BTRFS_QGROUP_STATUS_FLAG_RESCAN;



	if (err > 0 &&
@@ -2336,7 +2337,9 @@ static void btrfs_qgroup_rescan_worker(struct btrfs_work *work) 
	}

	btrfs_end_transaction(trans, fs_info->quota_root);



	if (err >= 0) {

	if (btrfs_fs_closing(fs_info)) {

		btrfs_info(fs_info, "qgroup scan paused");

	} else if (err >= 0) {

		btrfs_info(fs_info, "qgroup scan completed%s",

			err > 0 ? " (inconsistency flag cleared)" : "");

	} else {