From 7343dd61fd1b57c40cc06a5b5b5386df7f73c3ac Mon Sep 17 00:00:00 2001 From: Justin Maggard Date: Wed, 4 Nov 2015 15:56:16 -0800 Subject: [PATCH] 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: Justin Maggard Reviewed-by: Filipe Manana --- fs/btrfs/disk-io.c | 3 +++ fs/btrfs/qgroup.c | 9 ++++++--- 2 files changed, 9 insertions(+), 3 deletions(-) diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index 2d4667594681..1eb08393bff0 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -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 */ diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c index 46476c226395..75c0249702df 100644 --- a/fs/btrfs/qgroup.c +++ b/fs/btrfs/qgroup.c @@ -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); @@ -2307,7 +2307,8 @@ out: btrfs_free_path(path); mutex_lock(&fs_info->qgroup_rescan_lock); - fs_info->qgroup_flags &= ~BTRFS_QGROUP_STATUS_FLAG_RESCAN; + if (!btrfs_fs_closing(fs_info)) + fs_info->qgroup_flags &= ~BTRFS_QGROUP_STATUS_FLAG_RESCAN; if (err > 0 && fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT) { @@ -2336,7 +2337,9 @@ out: } 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 {