genhd: Annotate all part and part_tbl pointer dereferences

Annotate gendisk.part_tbl and disk_part_tbl.part dereferences with
rcu_dereference_protected(). This patch does not change the behavior
of the modified code but ensures that sparse does not complain about
disk->part_tbl manipulations nor about part_tbl->part accesses.
Additionally, improve documentation of the locking requirements of
the modified functions.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 10 insertions, 5 deletions

diff --git a/block/genhd.c b/block/genhd.c
index 3dc4d115480f..2367087cdb7c 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -1127,12 +1127,13 @@ static const struct attribute_group *disk_attr_groups[] = {
  * original ptbl is freed using RCU callback.
  *
  * LOCKING:
- * Matching bd_mutx locked.
+ * Matching bd_mutex locked or the caller is the only user of @disk.
  */
 static void disk_replace_part_tbl(struct gendisk *disk,
                                   struct disk_part_tbl *new_ptbl)
 {
-        struct disk_part_tbl *old_ptbl = disk->part_tbl;
+        struct disk_part_tbl *old_ptbl =
+                rcu_dereference_protected(disk->part_tbl, 1);
 
         rcu_assign_pointer(disk->part_tbl, new_ptbl);
 
@@ -1151,14 +1152,16 @@ static void disk_replace_part_tbl(struct gendisk *disk,
  * uses RCU to allow unlocked dereferencing for stats and other stuff.
  *
  * LOCKING:
- * Matching bd_mutex locked, might sleep.
+ * Matching bd_mutex locked or the caller is the only user of @disk.
+ * Might sleep.
  *
  * RETURNS:
  * 0 on success, -errno on failure.
  */
 int disk_expand_part_tbl(struct gendisk *disk, int partno)
 {
-        struct disk_part_tbl *old_ptbl = disk->part_tbl;
+        struct disk_part_tbl *old_ptbl =
+                rcu_dereference_protected(disk->part_tbl, 1);
         struct disk_part_tbl *new_ptbl;
         int len = old_ptbl ? old_ptbl->len : 0;
         int i, target;
@@ -1352,6 +1355,7 @@ EXPORT_SYMBOL(alloc_disk);
 struct gendisk *alloc_disk_node(int minors, int node_id)
 {
         struct gendisk *disk;
+        struct disk_part_tbl *ptbl;
 
         disk = kzalloc_node(sizeof(struct gendisk), GFP_KERNEL, node_id);
         if (disk) {
@@ -1365,7 +1369,8 @@ struct gendisk *alloc_disk_node(int minors, int node_id)
                         kfree(disk);
                         return NULL;
                 }
-                disk->part_tbl->part[0] = &disk->part0;
+                ptbl = rcu_dereference_protected(disk->part_tbl, 1);
+                rcu_assign_pointer(ptbl->part[0], &disk->part0);
 
                 /*
                  * set_capacity() and get_capacity() currently don't use