Revert "block: remove the -ERESTARTSYS handling in blkdev_get_by_dev"

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
Tested-by: Stoiko Ivanov <s.ivanov@proxmox.com>

patches/kernel/0009-Revert-block-remove-the-ERESTARTSYS-handling-in-blkd.patch

@@ -0,0 +1,40 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Thomas Lamprecht <t.lamprecht@proxmox.com>
+Date: Tue, 9 Nov 2021 12:01:12 +0100
+Subject: [PATCH] Revert "block: remove the -ERESTARTSYS handling in
+ blkdev_get_by_dev"
+
+This reverts commit a8ed1a0607cfa5478ff6009539f44790c4d0956d.
+
+It breaks ZFS sometimes:
+https://github.com/openzfs/zfs/issues/12301#issuecomment-873303739
+
+Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
+---
+ fs/block_dev.c | 6 ++++++
+ 1 file changed, 6 insertions(+)
+
+diff --git a/fs/block_dev.c b/fs/block_dev.c
+index e4a80bd4ddf1..4a14d28dd923 100644
+--- a/fs/block_dev.c
++++ b/fs/block_dev.c
+@@ -1436,6 +1436,10 @@ struct block_device *blkdev_get_by_dev(dev_t dev, fmode_t mode, void *holder)
+ 	if (ret)
+ 		return ERR_PTR(ret);
+ 
++	/*
++	 * If we lost a race with 'disk' being deleted, try again.  See md.c.
++	 */
++retry:
+ 	bdev = blkdev_get_no_open(dev);
+ 	if (!bdev)
+ 		return ERR_PTR(-ENXIO);
+@@ -1482,6 +1486,8 @@ struct block_device *blkdev_get_by_dev(dev_t dev, fmode_t mode, void *holder)
+ 	disk_unblock_events(disk);
+ put_blkdev:
+ 	blkdev_put_no_open(bdev);
++	if (ret == -ERESTARTSYS)
++		goto retry;
+ 	return ERR_PTR(ret);
+ }
+ EXPORT_SYMBOL(blkdev_get_by_dev);