Commit d2c609b8 authored by Jeff Mahoney's avatar Jeff Mahoney Committed by Chris Mason
Browse files

btrfs: properly track when rescan worker is running

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.

Cc: <> # v4.4+
Signed-off-by; Jeff Mahoney <>
Reviewed-by: default avatarQu Wenruo <>
Signed-off-by: default avatarDavid Sterba <>

Signed-off-by: default avatarChris Mason <>
parent eecba891
......@@ -1028,6 +1028,7 @@ 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;
......@@ -2304,6 +2304,7 @@ static void btrfs_init_qgroup(struct btrfs_fs_info *fs_info)
fs_info->quota_enabled = 0;
fs_info->pending_quota_state = 0;
fs_info->qgroup_ulist = NULL;
fs_info->qgroup_rescan_running = false;
......@@ -2303,6 +2303,10 @@ static void btrfs_qgroup_rescan_worker(struct btrfs_work *work)
int err = -ENOMEM;
int ret = 0;
fs_info->qgroup_rescan_running = true;
path = btrfs_alloc_path();
if (!path)
goto out;
......@@ -2369,6 +2373,9 @@ out:
fs_info->qgroup_rescan_running = false;
......@@ -2494,7 +2501,7 @@ int btrfs_qgroup_wait_for_completion(struct btrfs_fs_info *fs_info)
running = fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_RESCAN;
running = fs_info->qgroup_rescan_running;
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