From: Jeff Mahoney <jeffm@xxxxxxxx>
Commit 8d9eddad194 (Btrfs: fix qgroup rescan worker initialization)
fixed the issue with BTRFS_IOC_QUOTA_RESCAN_WAIT being racy, but
ended up reintroducing the hang-on-unmount bug that the commit it
intended to fix addressed.
The race this time is between qgroup_rescan_init setting
->qgroup_rescan_running = true and the worker starting. There are
many scenarios where we initialize the worker and never start it. The
completion btrfs_ioctl_quota_rescan_wait waits for will never come.
This can happen even without involving error handling, since mounting
the file system read-only returns between initializing the worker and
queueing it.
The right place to do it is when we're queuing the worker. The flag
really just means that btrfs_ioctl_quota_rescan_wait should wait for
a completion.
Since the BTRFS_QGROUP_STATUS_FLAG_RESCAN flag is overloaded to
refer to both runtime behavior and on-disk state, we introduce a new
fs_info->qgroup_rescan_ready to indicate that we're initialized and
waiting to start.
This patch introduces a new helper, queue_rescan_worker, that handles
most of the initialization, the two flags, and queuing the worker,
including races with unmount.
While we're at it, ->qgroup_rescan_running is protected only by the
->qgroup_rescan_mutex. btrfs_ioctl_quota_rescan_wait doesn't need
to take the spinlock too.
Fixes: 8d9eddad194 (Btrfs: fix qgroup rescan worker initialization)
Signed-off-by: Jeff Mahoney <jeffm@xxxxxxxx>
---
fs/btrfs/ctree.h | 2 ++
fs/btrfs/qgroup.c | 94 +++++++++++++++++++++++++++++++++----------------------
2 files changed, 58 insertions(+), 38 deletions(-)
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index da308774b8a4..4003498bb714 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1045,6 +1045,8 @@ struct btrfs_fs_info {
struct btrfs_workqueue *qgroup_rescan_workers;
struct completion qgroup_rescan_completion;
struct btrfs_work qgroup_rescan_work;
+ /* qgroup rescan worker is running or queued to run */
+ bool qgroup_rescan_ready;
bool qgroup_rescan_running; /* protected by qgroup_rescan_lock */
/* filesystem state */
diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index aa259d6986e1..466744741873 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -101,6 +101,7 @@ static int
qgroup_rescan_init(struct btrfs_fs_info *fs_info, u64 progress_objectid,
int init_flags);
static void qgroup_rescan_zero_tracking(struct btrfs_fs_info *fs_info);
+static void btrfs_qgroup_rescan_worker(struct btrfs_work *work);
/* must be called with qgroup_ioctl_lock held */
static struct btrfs_qgroup *find_qgroup_rb(struct btrfs_fs_info *fs_info,
@@ -2072,6 +2073,46 @@ int btrfs_qgroup_account_extents(struct btrfs_trans_handle *trans,
return ret;
}
+static void queue_rescan_worker(struct btrfs_fs_info *fs_info)
+{
+ mutex_lock(&fs_info->qgroup_rescan_lock);
+ if (btrfs_fs_closing(fs_info)) {
+ mutex_unlock(&fs_info->qgroup_rescan_lock);
+ return;
+ }
+
+ if (WARN_ON(!fs_info->qgroup_rescan_ready)) {
+ btrfs_warn(fs_info, "rescan worker not ready");
+ mutex_unlock(&fs_info->qgroup_rescan_lock);
+ return;
+ }
+ fs_info->qgroup_rescan_ready = false;
+
+ if (WARN_ON(fs_info->qgroup_rescan_running)) {
+ btrfs_warn(fs_info, "rescan worker already queued");
+ mutex_unlock(&fs_info->qgroup_rescan_lock);
+ return;
+ }
+
+ /*
+ * Being queued is enough for btrfs_qgroup_wait_for_completion
+ * to need to wait.
+ */
+ fs_info->qgroup_rescan_running = true;
+ init_completion(&fs_info->qgroup_rescan_completion);
+ mutex_unlock(&fs_info->qgroup_rescan_lock);
+
+ memset(&fs_info->qgroup_rescan_work, 0,
+ sizeof(fs_info->qgroup_rescan_work));
+
+ btrfs_init_work(&fs_info->qgroup_rescan_work,
+ btrfs_qgroup_rescan_helper,
+ btrfs_qgroup_rescan_worker, NULL, NULL);
+
+ btrfs_queue_work(fs_info->qgroup_rescan_workers,
+ &fs_info->qgroup_rescan_work);
+}
+
/*
* called from commit_transaction. Writes all changed qgroups to disk.
*/
@@ -2123,8 +2164,7 @@ int btrfs_run_qgroups(struct btrfs_trans_handle *trans,
ret = qgroup_rescan_init(fs_info, 0, 1);
if (!ret) {
qgroup_rescan_zero_tracking(fs_info);
- btrfs_queue_work(fs_info->qgroup_rescan_workers,
- &fs_info->qgroup_rescan_work);
+ queue_rescan_worker(fs_info);
}
ret = 0;
}
@@ -2607,6 +2647,10 @@ static void btrfs_qgroup_rescan_worker(struct btrfs_work *work)
if (!path)
goto out;
+ mutex_lock(&fs_info->qgroup_rescan_lock);
+ fs_info->qgroup_flags |= BTRFS_QGROUP_STATUS_FLAG_RESCAN;
+ mutex_unlock(&fs_info->qgroup_rescan_lock);
+
err = 0;
while (!err && !btrfs_fs_closing(fs_info)) {
trans = btrfs_start_transaction(fs_info->fs_root, 0);
@@ -2685,47 +2729,27 @@ qgroup_rescan_init(struct btrfs_fs_info *fs_info, u64 progress_objectid,
{
int ret = 0;
- if (!init_flags &&
- (!(fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_RESCAN) ||
- !(fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_ON))) {
+ if (!test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags)) {
ret = -EINVAL;
goto err;
}
mutex_lock(&fs_info->qgroup_rescan_lock);
- spin_lock(&fs_info->qgroup_lock);
-
- if (init_flags) {
- if (fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_RESCAN)
- ret = -EINPROGRESS;
- else if (!(fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_ON))
- ret = -EINVAL;
-
- if (ret) {
- spin_unlock(&fs_info->qgroup_lock);
- mutex_unlock(&fs_info->qgroup_rescan_lock);
- goto err;
- }
- fs_info->qgroup_flags |= BTRFS_QGROUP_STATUS_FLAG_RESCAN;
+ if (fs_info->qgroup_rescan_ready || fs_info->qgroup_rescan_running) {
+ mutex_unlock(&fs_info->qgroup_rescan_lock);
+ ret = -EINPROGRESS;
+ goto err;
}
memset(&fs_info->qgroup_rescan_progress, 0,
sizeof(fs_info->qgroup_rescan_progress));
fs_info->qgroup_rescan_progress.objectid = progress_objectid;
- init_completion(&fs_info->qgroup_rescan_completion);
- fs_info->qgroup_rescan_running = true;
+ fs_info->qgroup_rescan_ready = true;
- spin_unlock(&fs_info->qgroup_lock);
mutex_unlock(&fs_info->qgroup_rescan_lock);
- memset(&fs_info->qgroup_rescan_work, 0,
- sizeof(fs_info->qgroup_rescan_work));
- btrfs_init_work(&fs_info->qgroup_rescan_work,
- btrfs_qgroup_rescan_helper,
- btrfs_qgroup_rescan_worker, NULL, NULL);
-
- if (ret) {
err:
+ if (ret) {
btrfs_info(fs_info, "qgroup_rescan_init failed with %d", ret);
return ret;
}
@@ -2785,9 +2809,7 @@ btrfs_qgroup_rescan(struct btrfs_fs_info *fs_info)
qgroup_rescan_zero_tracking(fs_info);
- btrfs_queue_work(fs_info->qgroup_rescan_workers,
- &fs_info->qgroup_rescan_work);
-
+ queue_rescan_worker(fs_info);
return 0;
}
@@ -2798,9 +2820,7 @@ int btrfs_qgroup_wait_for_completion(struct btrfs_fs_info *fs_info,
int ret = 0;
mutex_lock(&fs_info->qgroup_rescan_lock);
- spin_lock(&fs_info->qgroup_lock);
running = fs_info->qgroup_rescan_running;
- spin_unlock(&fs_info->qgroup_lock);
mutex_unlock(&fs_info->qgroup_rescan_lock);
if (!running)
@@ -2819,12 +2839,10 @@ int btrfs_qgroup_wait_for_completion(struct btrfs_fs_info *fs_info,
* this is only called from open_ctree where we're still single threaded, thus
* locking is omitted here.
*/
-void
-btrfs_qgroup_rescan_resume(struct btrfs_fs_info *fs_info)
+void btrfs_qgroup_rescan_resume(struct btrfs_fs_info *fs_info)
{
if (fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_RESCAN)
- btrfs_queue_work(fs_info->qgroup_rescan_workers,
- &fs_info->qgroup_rescan_work);
+ queue_rescan_worker(fs_info);
}
/*
--
2.12.3
--
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