[PATCH] md/md-llbitmap: refuse reshape while llbitmap still needs sync

[Yu Kuai <yukuai@kernel.org>]

From: Yu Kuai <yukuai@fygo.io>

Reject reshape when llbitmap still contains NeedSync or Syncing bits.

This keeps reshape from starting until the current llbitmap state has
been reconciled.

Signed-off-by: Yu Kuai <yukuai@fygo.io>
---
 drivers/md/md-llbitmap.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/drivers/md/md-llbitmap.c b/drivers/md/md-llbitmap.c
index 52ab45f2a018..f45daf3be4d5 100644
--- a/drivers/md/md-llbitmap.c
+++ b/drivers/md/md-llbitmap.c
@@ -1677,10 +1677,33 @@ static void llbitmap_dirty_bits(struct mddev *mddev, unsigned long s,
 				unsigned long e)
 {
 	llbitmap_state_machine(mddev->bitmap, s, e, BitmapActionStartwrite);
 }
 
+static int llbitmap_reshape_can_start(struct mddev *mddev)
+{
+	struct llbitmap *llbitmap = mddev->bitmap;
+	unsigned long chunk;
+	int ret = 0;
+
+	if (!llbitmap)
+		return 0;
+
+	mutex_lock(&mddev->bitmap_info.mutex);
+	for (chunk = 0; chunk < llbitmap->chunks; chunk++) {
+		enum llbitmap_state state = llbitmap_read(llbitmap, chunk);
+
+		if (state == BitNeedSync || state == BitSyncing) {
+			ret = -EBUSY;
+			break;
+		}
+	}
+	mutex_unlock(&mddev->bitmap_info.mutex);
+
+	return ret;
+}
+
 static void llbitmap_reshape_finish(struct mddev *mddev)
 {
 	struct llbitmap *llbitmap = mddev->bitmap;
 
 	if (mddev->pers->quiesce)
@@ -1996,10 +2019,11 @@ static struct bitmap_operations llbitmap_ops = {
 	.update_sb		= llbitmap_update_sb,
 	.get_stats		= llbitmap_get_stats,
 	.dirty_bits		= llbitmap_dirty_bits,
 	.prepare_range		= llbitmap_prepare_range,
 	.reshape_finish		= llbitmap_reshape_finish,
+	.reshape_can_start	= llbitmap_reshape_can_start,
 	.write_all		= llbitmap_write_all,
 
 	.groups			= md_llbitmap_groups,
 };
 
-- 
2.51.0