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Date: Sat, 16 Dec 2023 19:11:05 -0800
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Subject: Re: [syzbot] [block?] INFO: task hung in bdev_release
From: syzbot <syzbot+4da851837827326a7cd4@syzkaller.appspotmail.com>
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Subject: [block?] INFO: task hung in bdev_release
Author: eadavis@qq.com

please test task hung in bdev_release

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git  8c9660f65153

diff --git a/block/bdev.c b/block/bdev.c
index 6f73b02d549c..95be32bc8dea 100644
--- a/block/bdev.c
+++ b/block/bdev.c
@@ -938,6 +938,7 @@ struct bdev_handle *bdev_open_by_path(const char *path, blk_mode_t mode,
 	if (error)
 		return ERR_PTR(error);
 
+	printk("dev: %u, path: %s, holder: %p, %s\n", dev, path, holder, __func__);
 	handle = bdev_open_by_dev(dev, mode, holder, hops);
 	if (!IS_ERR(handle) && (mode & BLK_OPEN_WRITE) &&
 	    bdev_read_only(handle->bdev)) {
@@ -964,6 +965,7 @@ void bdev_release(struct bdev_handle *handle)
 	if (atomic_read(&bdev->bd_openers) == 1)
 		sync_blockdev(bdev);
 
+	printk("nxt om, b: %p, dk: %p, %s\n", bdev, disk, __func__);
 	mutex_lock(&disk->open_mutex);
 	bdev_yield_write_access(bdev, handle->mode);
 
@@ -982,6 +984,7 @@ void bdev_release(struct bdev_handle *handle)
 	else
 		blkdev_put_whole(bdev);
 	mutex_unlock(&disk->open_mutex);
+	printk("out om, b: %p, dk: %p, %s\n", bdev, disk, __func__);
 
 	module_put(disk->fops->owner);
 	blkdev_put_no_open(bdev);
@@ -1092,7 +1095,8 @@ void sync_bdevs(bool wait)
 		old_inode = inode;
 		bdev = I_BDEV(inode);
 
-		mutex_lock(&bdev->bd_disk->open_mutex);
+		printk("in, b: %p, dk: %p, %s\n", bdev, bdev->bd_disk, __func__);
+		mutex_lock(&bdev->bd_disk->sync_mutex);
 		if (!atomic_read(&bdev->bd_openers)) {
 			; /* skip */
 		} else if (wait) {
@@ -1106,7 +1110,8 @@ void sync_bdevs(bool wait)
 		} else {
 			filemap_fdatawrite(inode->i_mapping);
 		}
-		mutex_unlock(&bdev->bd_disk->open_mutex);
+		mutex_unlock(&bdev->bd_disk->sync_mutex);
+		printk("out, b: %p, dk: %p, %s\n", bdev, bdev->bd_disk, __func__);
 
 		spin_lock(&blockdev_superblock->s_inode_list_lock);
 	}
diff --git a/block/genhd.c b/block/genhd.c
index 13db3a7943d8..da44d4739915 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -1355,6 +1355,7 @@ struct gendisk *__alloc_disk_node(struct request_queue *q, int node_id,
 
 	disk->node_id = node_id;
 	mutex_init(&disk->open_mutex);
+	mutex_init(&disk->sync_mutex);
 	xa_init(&disk->part_tbl);
 	if (xa_insert(&disk->part_tbl, 0, disk->part0, GFP_KERNEL))
 		goto out_destroy_part_tbl;
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index b6414e1e645b..c302df0caebf 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -475,10 +475,11 @@ static enum blk_eh_timer_return nbd_xmit_timeout(struct request *req)
 		 */
 		struct nbd_sock *nsock = config->socks[cmd->index];
 		cmd->retries++;
-		dev_info(nbd_to_dev(nbd), "Possible stuck request %p: control (%s@%llu,%uB). Runtime %u seconds\n",
+		dev_info(nbd_to_dev(nbd), "Possible stuck request %p: control (%s@%llu,%uB). Runtime %u seconds, nbd: %p, d: %p\n",
 			req, nbdcmd_to_ascii(req_to_nbd_cmd_type(req)),
 			(unsigned long long)blk_rq_pos(req) << 9,
-			blk_rq_bytes(req), (req->timeout / HZ) * cmd->retries);
+			blk_rq_bytes(req), (req->timeout / HZ) * cmd->retries,
+			nbd, nbd->disk);
 
 		mutex_lock(&nsock->tx_lock);
 		if (cmd->cookie != nsock->cookie) {
@@ -1425,6 +1426,7 @@ static int nbd_start_device(struct nbd_device *nbd)
 		args->index = i;
 		queue_work(nbd->recv_workq, &args->work);
 	}
+	printk("bs: %lld, blks: %lld, %s\n", config->bytesize, nbd_blksize(config), __func__);
 	return nbd_set_size(nbd, config->bytesize, nbd_blksize(config));
 }
 
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 3f8a21cd9233..31c6a7d6a74c 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -161,6 +161,7 @@ struct gendisk {
 #define GD_OWNS_QUEUE			6
 
 	struct mutex open_mutex;	/* open/close mutex */
+	struct mutex sync_mutex;	/* sync mutex */
 	unsigned open_partitions;	/* number of open partitions */
 
 	struct backing_dev_info	*bdi;