bcache: struct cache_sb is only for in-memory super block now

We have struct cache_sb_disk for on-disk super block already, it is unnecessary to keep the in-memory super block format exactly mapping to the on-disk struct layout. This patch adds code comments to notice that struct cache_sb is not exactly mapping to cache_sb_disk, and removes the useless member csum and pad[5]. Although struct cache_sb does not belong to uapi, but there are still some on-disk format related macros reference it and it is unncessary to get rid of such dependency now. So struct cache_sb will continue to stay in include/uapi/linux/bache.h for now.

Coly Li committed 6 years ago

Commit 4c1ccd01 parent 198efa31 file · +6 −4Browse files

Showing the changes to include/uapi/linux (1 of 1 file). Show all

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include/uapi/linux/bcache.h+6−4

 	__le64			d[SB_JOURNAL_BUCKETS];	/* journal buckets */
 };
+/*
+ * This is for in-memory bcache super block.
+ * NOTE: cache_sb is NOT exactly mapping to cache_sb_disk, the member
+ *       size, ordering and even whole struct size may be different
+ *       from cache_sb_disk.
+ */
 struct cache_sb {
-	__u64			csum;
 	__u64			offset;	/* sector where this sb was written */
 	__u64			version;
 	__u64			feature_incompat;
 	__u64			feature_ro_compat;
-	__u64			pad[5];
 	union {
 	struct {
 		/* Cache devices */
 		__u16		block_size;	/* sectors */
 		__u16		bucket_size;	/* sectors */
 		__u16		nr_in_set;
 		__u16		nr_this_dev;
 	};