Merge tag 'for-6.3/dio-2023-02-16' of git://git.kernel.dk/linux

Pull legacy dio update from Jens Axboe:
 "We only have a few file systems that use the old dio code, make them
  select it rather than build it unconditionally"

* tag 'for-6.3/dio-2023-02-16' of git://git.kernel.dk/linux:
  fs: build the legacy direct I/O code conditionally
  fs: move sb_init_dio_done_wq out of direct-io.c

1 files changed, 24 insertions, 0 deletions

diff --git a/fs/super.c b/fs/super.c
index 8e531174e7c2..84332d5cb817 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -1776,3 +1776,27 @@ int thaw_super(struct super_block *sb)
 	return thaw_super_locked(sb);
 }
 EXPORT_SYMBOL(thaw_super);
+
+/*
+ * Create workqueue for deferred direct IO completions. We allocate the
+ * workqueue when it's first needed. This avoids creating workqueue for
+ * filesystems that don't need it and also allows us to create the workqueue
+ * late enough so the we can include s_id in the name of the workqueue.
+ */
+int sb_init_dio_done_wq(struct super_block *sb)
+{
+	struct workqueue_struct *old;
+	struct workqueue_struct *wq = alloc_workqueue("dio/%s",
+						      WQ_MEM_RECLAIM, 0,
+						      sb->s_id);
+	if (!wq)
+		return -ENOMEM;
+	/*
+	 * This has to be atomic as more DIOs can race to create the workqueue
+	 */
+	old = cmpxchg(&sb->s_dio_done_wq, NULL, wq);
+	/* Someone created workqueue before us? Free ours... */
+	if (old)
+		destroy_workqueue(wq);
+	return 0;
+}