mbcache: make mbcache naming more generic

Make names more generic so that mbcache usage is not limited to
block sharing. In a subsequent patch in the series
("ext4: xattr inode deduplication"), we start using the mbcache code
for sharing xattr inodes. With that patch, old mb_cache_entry.e_block
field could be holding either a block number or an inode number.

Signed-off-by: Tahsin Erdogan <[e-mail]>
Signed-off-by: Theodore Ts'o <[e-mail]>

fs/ext2/xattr.c

···
 			 * This must happen under buffer lock for
 			 * ext2_xattr_set2() to reliably detect modified block
 			 */
-			mb_cache_entry_delete_block(EXT2_SB(sb)->s_mb_cache,
-						    hash, bh->b_blocknr);
+			mb_cache_entry_delete(EXT2_SB(sb)->s_mb_cache, hash,
+					      bh->b_blocknr);
 
 			/* keep the buffer locked while modifying it. */
 		} else {
···
 			 * This must happen under buffer lock for
 			 * ext2_xattr_set2() to reliably detect freed block
 			 */
-			mb_cache_entry_delete_block(ext2_mb_cache,
-						    hash, old_bh->b_blocknr);
+			mb_cache_entry_delete(ext2_mb_cache, hash,
+					      old_bh->b_blocknr);
 			/* Free the old block. */
 			ea_bdebug(old_bh, "freeing");
 			ext2_free_blocks(inode, old_bh->b_blocknr, 1);
···
 		 * This must happen under buffer lock for ext2_xattr_set2() to
 		 * reliably detect freed block
 		 */
-		mb_cache_entry_delete_block(EXT2_SB(inode->i_sb)->s_mb_cache,
-					    hash, bh->b_blocknr);
+		mb_cache_entry_delete(EXT2_SB(inode->i_sb)->s_mb_cache, hash,
+				      bh->b_blocknr);
 		ext2_free_blocks(inode, EXT2_I(inode)->i_file_acl, 1);
 		get_bh(bh);
 		bforget(bh);
···
 	while (ce) {
 		struct buffer_head *bh;
 
-		bh = sb_bread(inode->i_sb, ce->e_block);
+		bh = sb_bread(inode->i_sb, ce->e_value);
 		if (!bh) {
 			ext2_error(inode->i_sb, "ext2_xattr_cache_find",
 				"inode %ld: block %ld read error",
-				inode->i_ino, (unsigned long) ce->e_block);
+				inode->i_ino, (unsigned long) ce->e_value);
 		} else {
 			lock_buffer(bh);
 			/*
···
 			} else if (le32_to_cpu(HDR(bh)->h_refcount) >
 				   EXT2_XATTR_REFCOUNT_MAX) {
 				ea_idebug(inode, "block %ld refcount %d>%d",
-					  (unsigned long) ce->e_block,
+					  (unsigned long) ce->e_value,
 					  le32_to_cpu(HDR(bh)->h_refcount),
 					  EXT2_XATTR_REFCOUNT_MAX);
 			} else if (!ext2_xattr_cmp(header, HDR(bh))) {

fs/ext4/xattr.c

···
 		 * This must happen under buffer lock for
 		 * ext4_xattr_block_set() to reliably detect freed block
 		 */
-		mb_cache_entry_delete_block(ext4_mb_cache, hash, bh->b_blocknr);
+		mb_cache_entry_delete(ext4_mb_cache, hash, bh->b_blocknr);
 		get_bh(bh);
 		unlock_buffer(bh);
 		ext4_free_blocks(handle, inode, bh, 0, 1,
···
 			 * ext4_xattr_block_set() to reliably detect modified
 			 * block
 			 */
-			mb_cache_entry_delete_block(ext4_mb_cache, hash,
-						    bs->bh->b_blocknr);
+			mb_cache_entry_delete(ext4_mb_cache, hash,
+					      bs->bh->b_blocknr);
 			ea_bdebug(bs->bh, "modifying in-place");
 			error = ext4_xattr_set_entry(i, s, handle, inode);
 			if (!error) {
···
 	while (ce) {
 		struct buffer_head *bh;
 
-		bh = sb_bread(inode->i_sb, ce->e_block);
+		bh = sb_bread(inode->i_sb, ce->e_value);
 		if (!bh) {
 			EXT4_ERROR_INODE(inode, "block %lu read error",
-					 (unsigned long) ce->e_block);
+					 (unsigned long)ce->e_value);
 		} else if (ext4_xattr_cmp(header, BHDR(bh)) == 0) {
 			*pce = ce;
 			return bh;

fs/mbcache.c

···
 /*
  * Mbcache is a simple key-value store. Keys need not be unique, however
  * key-value pairs are expected to be unique (we use this fact in
- * mb_cache_entry_delete_block()).
+ * mb_cache_entry_delete()).
  *
  * Ext2 and ext4 use this cache for deduplication of extended attribute blocks.
  * They use hash of a block contents as a key and block number as a value.
···
  * @cache - cache where the entry should be created
  * @mask - gfp mask with which the entry should be allocated
  * @key - key of the entry
- * @block - block that contains data
- * @reusable - is the block reusable by other inodes?
+ * @value - value of the entry
+ * @reusable - is the entry reusable by others?
  *
- * Creates entry in @cache with key @key and records that data is stored in
- * block @block. The function returns -EBUSY if entry with the same key
- * and for the same block already exists in cache. Otherwise 0 is returned.
+ * Creates entry in @cache with key @key and value @value. The function returns
+ * -EBUSY if entry with the same key and value already exists in cache.
+ * Otherwise 0 is returned.
  */
 int mb_cache_entry_create(struct mb_cache *cache, gfp_t mask, u32 key,
-			  sector_t block, bool reusable)
+			  u64 value, bool reusable)
 {
 	struct mb_cache_entry *entry, *dup;
 	struct hlist_bl_node *dup_node;
···
 	/* One ref for hash, one ref returned */
 	atomic_set(&entry->e_refcnt, 1);
 	entry->e_key = key;
-	entry->e_block = block;
+	entry->e_value = value;
 	entry->e_reusable = reusable;
 	head = mb_cache_entry_head(cache, key);
 	hlist_bl_lock(head);
 	hlist_bl_for_each_entry(dup, dup_node, head, e_hash_list) {
-		if (dup->e_key == key && dup->e_block == block) {
+		if (dup->e_key == key && dup->e_value == value) {
 			hlist_bl_unlock(head);
 			kmem_cache_free(mb_entry_cache, entry);
 			return -EBUSY;
···
 EXPORT_SYMBOL(mb_cache_entry_find_next);
 
 /*
- * mb_cache_entry_get - get a cache entry by block number (and key)
+ * mb_cache_entry_get - get a cache entry by value (and key)
  * @cache - cache we work with
- * @key - key of block number @block
- * @block - block number
+ * @key - key
+ * @value - value
  */
 struct mb_cache_entry *mb_cache_entry_get(struct mb_cache *cache, u32 key,
-					  sector_t block)
+					  u64 value)
 {
 	struct hlist_bl_node *node;
 	struct hlist_bl_head *head;
···
 	head = mb_cache_entry_head(cache, key);
 	hlist_bl_lock(head);
 	hlist_bl_for_each_entry(entry, node, head, e_hash_list) {
-		if (entry->e_key == key && entry->e_block == block) {
+		if (entry->e_key == key && entry->e_value == value) {
 			atomic_inc(&entry->e_refcnt);
 			goto out;
 		}
···
 }
 EXPORT_SYMBOL(mb_cache_entry_get);
 
-/* mb_cache_entry_delete_block - remove information about block from cache
+/* mb_cache_entry_delete - remove a cache entry
  * @cache - cache we work with
- * @key - key of block @block
- * @block - block number
+ * @key - key
+ * @value - value
  *
- * Remove entry from cache @cache with key @key with data stored in @block.
+ * Remove entry from cache @cache with key @key and value @value.
  */
-void mb_cache_entry_delete_block(struct mb_cache *cache, u32 key,
-				 sector_t block)
+void mb_cache_entry_delete(struct mb_cache *cache, u32 key, u64 value)
 {
 	struct hlist_bl_node *node;
 	struct hlist_bl_head *head;
···
 	head = mb_cache_entry_head(cache, key);
 	hlist_bl_lock(head);
 	hlist_bl_for_each_entry(entry, node, head, e_hash_list) {
-		if (entry->e_key == key && entry->e_block == block) {
+		if (entry->e_key == key && entry->e_value == value) {
 			/* We keep hash list reference to keep entry alive */
 			hlist_bl_del_init(&entry->e_hash_list);
 			hlist_bl_unlock(head);
···
 	}
 	hlist_bl_unlock(head);
 }
-EXPORT_SYMBOL(mb_cache_entry_delete_block);
+EXPORT_SYMBOL(mb_cache_entry_delete);
 
 /* mb_cache_entry_touch - cache entry got used
  * @cache - cache the entry belongs to

include/linux/mbcache.h

···
 	u32			e_key;
 	u32			e_referenced:1;
 	u32			e_reusable:1;
-	/* Block number of hashed block - stable during lifetime of the entry */
-	sector_t		e_block;
+	/* User provided value - stable during lifetime of the entry */
+	u64			e_value;
 };
 
 struct mb_cache *mb_cache_create(int bucket_bits);
 void mb_cache_destroy(struct mb_cache *cache);
 
 int mb_cache_entry_create(struct mb_cache *cache, gfp_t mask, u32 key,
-			  sector_t block, bool reusable);
+			  u64 value, bool reusable);
 void __mb_cache_entry_free(struct mb_cache_entry *entry);
 static inline int mb_cache_entry_put(struct mb_cache *cache,
 				     struct mb_cache_entry *entry)
···
 	return 1;
 }
 
-void mb_cache_entry_delete_block(struct mb_cache *cache, u32 key,
-				  sector_t block);
+void mb_cache_entry_delete(struct mb_cache *cache, u32 key, u64 value);
 struct mb_cache_entry *mb_cache_entry_get(struct mb_cache *cache, u32 key,
-					  sector_t block);
+					  u64 value);
 struct mb_cache_entry *mb_cache_entry_find_first(struct mb_cache *cache,
 						 u32 key);
 struct mb_cache_entry *mb_cache_entry_find_next(struct mb_cache *cache,