btrfs: compression: inline free_workspace

Replace indirect calls to free_workspace by switch and calls to the
specific callbacks. This is mainly to get rid of the indirection due to
spectre vulnerability mitigations.
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/compression.c

@@ -912,7 +912,6 @@ static struct list_head *alloc_heuristic_ws(unsigned int level)
 
 const struct btrfs_compress_op btrfs_heuristic_compress = {
 	.workspace_manager = &heuristic_wsm,
-	.free_workspace = free_heuristic_ws,
 };
 
 static const struct btrfs_compress_op * const btrfs_compress_op[] = {
@@ -939,6 +938,22 @@ static struct list_head *alloc_workspace(int type, unsigned int level)
 	}
 }
 
+static void free_workspace(int type, struct list_head *ws)
+{
+	switch (type) {
+	case BTRFS_COMPRESS_NONE: return free_heuristic_ws(ws);
+	case BTRFS_COMPRESS_ZLIB: return zlib_free_workspace(ws);
+	case BTRFS_COMPRESS_LZO:  return lzo_free_workspace(ws);
+	case BTRFS_COMPRESS_ZSTD: return zstd_free_workspace(ws);
+	default:
+		/*
+		 * This can't happen, the type is validated several times
+		 * before we get here.
+		 */
+		BUG();
+	}
+}
+
 static void btrfs_init_workspace_manager(int type)
 {
 	const struct btrfs_compress_op *ops = btrfs_compress_op[type];
@@ -976,7 +991,7 @@ static void btrfs_cleanup_workspace_manager(int type)
 	while (!list_empty(&wsman->idle_ws)) {
 		ws = wsman->idle_ws.next;
 		list_del(ws);
-		wsman->ops->free_workspace(ws);
+		free_workspace(type, ws);
 		atomic_dec(&wsman->total_ws);
 	}
 }
@@ -1111,7 +1126,7 @@ void btrfs_put_workspace(int type, struct list_head *ws)
 	}
 	spin_unlock(ws_lock);
 
-	wsm->ops->free_workspace(ws);
+	free_workspace(type, ws);
 	atomic_dec(total_ws);
 wake:
 	cond_wake_up(ws_wait);

fs/btrfs/compression.h

@@ -124,8 +124,6 @@ struct list_head *btrfs_get_workspace(int type, unsigned int level);
 void btrfs_put_workspace(int type, struct list_head *ws);
 
 struct btrfs_compress_op {
-	void (*free_workspace)(struct list_head *workspace);
-
 	struct workspace_manager *workspace_manager;
 	/* Maximum level supported by the compression algorithm */
 	unsigned int max_level;

fs/btrfs/lzo.c

@@ -484,7 +484,6 @@ int lzo_decompress(struct list_head *ws, unsigned char *data_in,
 
 const struct btrfs_compress_op btrfs_lzo_compress = {
 	.workspace_manager	= &wsm,
-	.free_workspace		= lzo_free_workspace,
 	.max_level		= 1,
 	.default_level		= 1,
 };

fs/btrfs/zlib.c

@@ -400,7 +400,6 @@ int zlib_decompress(struct list_head *ws, unsigned char *data_in,
 
 const struct btrfs_compress_op btrfs_zlib_compress = {
 	.workspace_manager	= &wsm,
-	.free_workspace		= zlib_free_workspace,
 	.max_level		= 9,
 	.default_level		= BTRFS_ZLIB_DEFAULT_LEVEL,
 };

fs/btrfs/zstd.c

@@ -708,7 +708,6 @@ int zstd_decompress(struct list_head *ws, unsigned char *data_in,
 const struct btrfs_compress_op btrfs_zstd_compress = {
 	/* ZSTD uses own workspace manager */
 	.workspace_manager = NULL,
-	.free_workspace = zstd_free_workspace,
 	.max_level	= ZSTD_BTRFS_MAX_LEVEL,
 	.default_level	= ZSTD_BTRFS_DEFAULT_LEVEL,
 };