[PATCH 2/3] xfs_scrub: fix nr_dirs accounting problems

["Darrick J. Wong" <darrick.wong@oracle.com>]

From: Darrick J. Wong <darrick.wong@oracle.com>

When we're scanning the directory tree, we bump nr_dirs every time we
think we're going to queue a new directory to process, and we decrement
it every time we're finished doing something with a directory
(successful or not).  We forgot to undo a counter increment when
workqueue_add fails, so refactor the code into helpers and call them
as necessary for correct operation.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
---
 scrub/vfs.c |   42 +++++++++++++++++++++++++++++-------------
 1 file changed, 29 insertions(+), 13 deletions(-)


diff --git a/scrub/vfs.c b/scrub/vfs.c
index add4e815..f8bc98c0 100644
--- a/scrub/vfs.c
+++ b/scrub/vfs.c
@@ -45,6 +45,32 @@ struct scan_fs_tree_dir {
 
 static void scan_fs_dir(struct workqueue *wq, xfs_agnumber_t agno, void *arg);
 
+/* Increment the number of directories that are queued for processing. */
+static void
+inc_nr_dirs(
+	struct scan_fs_tree	*sft)
+{
+	pthread_mutex_lock(&sft->lock);
+	sft->nr_dirs++;
+	pthread_mutex_unlock(&sft->lock);
+}
+
+/*
+ * Decrement the number of directories that are queued for processing and if
+ * we ran out of dirs to process, wake up anyone who was waiting for processing
+ * to finish.
+ */
+static void
+dec_nr_dirs(
+	struct scan_fs_tree	*sft)
+{
+	pthread_mutex_lock(&sft->lock);
+	sft->nr_dirs--;
+	if (sft->nr_dirs == 0)
+		pthread_cond_signal(&sft->wakeup);
+	pthread_mutex_unlock(&sft->lock);
+}
+
 /* Queue a directory for scanning. */
 static bool
 queue_subdir(
@@ -72,15 +98,10 @@ queue_subdir(
 	new_sftd->sft = sft;
 	new_sftd->rootdir = is_rootdir;
 
-	pthread_mutex_lock(&sft->lock);
-	sft->nr_dirs++;
-	pthread_mutex_unlock(&sft->lock);
+	inc_nr_dirs(sft);
 	error = workqueue_add(wq, scan_fs_dir, 0, new_sftd);
 	if (error) {
-		/*
-		 * XXX: need to decrement nr_dirs here; will do that in the
-		 * next patch.
-		 */
+		dec_nr_dirs(sft);
 		str_info(ctx, ctx->mntpoint,
 _("Could not queue subdirectory scan work."));
 		goto out_path;
@@ -180,12 +201,7 @@ scan_fs_dir(
 		str_errno(ctx, sftd->path);
 
 out:
-	pthread_mutex_lock(&sft->lock);
-	sft->nr_dirs--;
-	if (sft->nr_dirs == 0)
-		pthread_cond_signal(&sft->wakeup);
-	pthread_mutex_unlock(&sft->lock);
-
+	dec_nr_dirs(sft);
 	free(sftd->path);
 	free(sftd);
 }