[Devel] [PATCH rh7] cbt: add uuid arg to blk_cbt_map_copy_once()

[Maxim Patlasov]

The caller must specify explicitly the uuid of CBT mask to copy. This will
help to avoid collision between applications performing backup: the second
will get EINVAL if it attempts to collide with the first.

https://jira.sw.ru/browse/PSBM-45000
---
 block/blk-cbt.c        |   10 ++++++++--
 include/linux/blkdev.h |    5 +++--
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/block/blk-cbt.c b/block/blk-cbt.c
index 850fd7e..8c52bd8 100644
--- a/block/blk-cbt.c
+++ b/block/blk-cbt.c
@@ -278,8 +278,9 @@ err_cbt:
 	return ERR_PTR(-ENOMEM);
 }
 
-int blk_cbt_map_copy_once(struct request_queue *q, struct page ***map_ptr,
-			  blkcnt_t *block_max, blkcnt_t *block_bits)
+int blk_cbt_map_copy_once(struct request_queue *q, __u8 *uuid,
+			  struct page ***map_ptr, blkcnt_t *block_max,
+			  blkcnt_t *block_bits)
 {
 	struct cbt_info *cbt;
 	struct page **map;
@@ -293,6 +294,11 @@ int blk_cbt_map_copy_once(struct request_queue *q, struct page ***map_ptr,
 	BUG_ON(!cbt->map);
 	BUG_ON(!cbt->block_max);
 
+	if (!uuid || memcmp(uuid, cbt->uuid, sizeof(cbt->uuid))) {
+		mutex_unlock(&cbt_mutex);
+		return -EINVAL;
+	}
+
 	cbt_flush_cache(cbt);
 
 	npages = NR_PAGES(cbt->block_max);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 7ae962a..56c3a08 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1651,8 +1651,9 @@ extern void blk_cbt_update_size(struct block_device *bdev);
 extern void blk_cbt_release(struct request_queue *q);
 extern void blk_cbt_bio_queue(struct request_queue *q, struct bio *bio);
 extern int blk_cbt_ioctl(struct block_device *bdev, unsigned cmd, char __user *arg);
-extern int blk_cbt_map_copy_once(struct request_queue *q, struct page ***map_ptr,
-				 blkcnt_t *block_max, blkcnt_t *block_bits);
+extern int blk_cbt_map_copy_once(struct request_queue *q, __u8 *uuid,
+				 struct page ***map_ptr, blkcnt_t *block_max,
+				 blkcnt_t *block_bits);
 #else /* CONFIG_BLK_DEV_CBT */
 static inline void blk_cbt_update_size(struct block_device *bdev)
 {