Re: [PATCH 1/5] block: add flag for add_disk() completion notation

Often drivers may have complex setups where it is not
clear if their disk completed their respective *add_disk*()
call. They either have to invent a setting or, they
incorrectly use GENHD_FL_UP. Using GENHD_FL_UP however is
used internally so we know when we can add / remove
partitions safely. We can easily fail along the way
prior to add_disk() completing and still have
GENHD_FL_UP set, so it would not be correct in that case
to call del_gendisk() on the disk.

Provide a new flag then which allows us to check if
*add_disk*() completed, and conversely just make
del_gendisk() check for this for drivers so that
they can safely call del_gendisk() and we'll figure
it out if it is safe for you to call this.

Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
---
 block/genhd.c         |  8 ++++++++
 include/linux/genhd.h | 11 ++++++++++-
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/block/genhd.c b/block/genhd.c
index af4d2ab4a633..a858eed05e55 100644
--- a/block/genhd.c
+++ b/block/genhd.c

@@ -539,6 +539,8 @@ static void __device_add_disk(struct device *parent, struct gendisk *disk,
 
 	disk_add_events(disk);
 	blk_integrity_add(disk);
+
+	disk->flags |= GENHD_FL_DISK_ADDED;

+ * Drivers can safely call this even if they are not sure if the respective
+ * __device_add_disk() call succeeded.
+ *
  * Drivers exist which depend on the release of the gendisk to be synchronous,
  * it should not be deferred.
  *

@@ -578,6 +583,9 @@ void del_gendisk(struct gendisk *disk)
 {
 	might_sleep();
 
+	if (!blk_disk_added(disk))
+		return;