bcachefs: Add vmalloc fallback for decompress workspace

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/compress.c

@@ -607,7 +607,7 @@ static int __bch2_fs_compress_init(struct bch_fs *c, u64 features)
 	}
 
 	if (!mempool_initialized(&c->decompress_workspace)) {
-		ret = mempool_init_kmalloc_pool(
+		ret = mempool_init_kvpmalloc_pool(
 				&c->decompress_workspace,
 				1, decompress_workspace_size);
 		if (ret)