[PATCH 4.4 087/113] btrfs: properly track when rescan worker is running
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date: 2016-09-05 16:55:26
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4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jeff Mahoney <redacted> commit d2c609b834d62f1e91f1635a27dca29f7806d3d6 upstream. The qgroup_flags field is overloaded such that it reflects the on-disk status of qgroups and the runtime state. The BTRFS_QGROUP_STATUS_FLAG_RESCAN flag is used to indicate that a rescan operation is in progress, but if the file system is unmounted while a rescan is running, the rescan operation is paused. If the file system is then mounted read-only, the flag will still be present but the rescan operation will not have been resumed. When we go to umount, btrfs_qgroup_wait_for_completion will see the flag and interpret it to mean that the rescan worker is still running and will wait for a completion that will never come. This patch uses a separate flag to indicate when the worker is running. The locking and state surrounding the qgroup rescan worker needs a lot of attention beyond this patch but this is enough to avoid a hung umount. Signed-off-by; Jeff Mahoney [off-list ref] Reviewed-by: Qu Wenruo <redacted> Signed-off-by: David Sterba <dsterba@suse.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Chris Mason <clm@fb.com> --- fs/btrfs/ctree.h | 1 + fs/btrfs/disk-io.c | 1 + fs/btrfs/qgroup.c | 9 ++++++++- 3 files changed, 10 insertions(+), 1 deletion(-)
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h@@ -1770,6 +1770,7 @@ struct btrfs_fs_info { struct btrfs_workqueue *qgroup_rescan_workers; struct completion qgroup_rescan_completion; struct btrfs_work qgroup_rescan_work; + bool qgroup_rescan_running; /* protected by qgroup_rescan_lock */ /* filesystem state */ unsigned long fs_state; --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c
@@ -2276,6 +2276,7 @@ static void btrfs_init_qgroup(struct btr fs_info->quota_enabled = 0; fs_info->pending_quota_state = 0; fs_info->qgroup_ulist = NULL; + fs_info->qgroup_rescan_running = false; mutex_init(&fs_info->qgroup_rescan_lock); } --- a/fs/btrfs/qgroup.c +++ b/fs/btrfs/qgroup.c
@@ -2283,6 +2283,10 @@ static void btrfs_qgroup_rescan_worker(s int err = -ENOMEM; int ret = 0; + mutex_lock(&fs_info->qgroup_rescan_lock); + fs_info->qgroup_rescan_running = true; + mutex_unlock(&fs_info->qgroup_rescan_lock); + path = btrfs_alloc_path(); if (!path) goto out;
@@ -2349,6 +2353,9 @@ out: } done: + mutex_lock(&fs_info->qgroup_rescan_lock); + fs_info->qgroup_rescan_running = false; + mutex_unlock(&fs_info->qgroup_rescan_lock); complete_all(&fs_info->qgroup_rescan_completion); }
@@ -2475,7 +2482,7 @@ int btrfs_qgroup_wait_for_completion(str mutex_lock(&fs_info->qgroup_rescan_lock); spin_lock(&fs_info->qgroup_lock); - running = fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_RESCAN; + running = fs_info->qgroup_rescan_running; spin_unlock(&fs_info->qgroup_lock); mutex_unlock(&fs_info->qgroup_rescan_lock);