fsverity: use WARN_ON_ONCE instead of WARN_ON

As per Linus's suggestion
(https://lore.kernel.org/r/CAHk-=whefxRGyNGzCzG6BVeM=5vnvgb-XhSeFJVxJyAxAF8XRA@mail.gmail.com),
use WARN_ON_ONCE instead of WARN_ON.  This barely adds any extra
overhead, and it makes it so that if any of these ever becomes reachable
(they shouldn't, but that's the point), the logs can't be flooded.

Link: https://lore.kernel.org/r/20230406181542.38894-1-ebiggers@kernel.orgReviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>

fs/verity/enable.c

@@ -165,7 +165,7 @@ static int build_merkle_tree(struct file *filp,
 		}
 	}
 	/* The root hash was filled by the last call to hash_one_block(). */
-	if (WARN_ON(buffers[num_levels].filled != params->digest_size)) {
+	if (WARN_ON_ONCE(buffers[num_levels].filled != params->digest_size)) {
 		err = -EINVAL;
 		goto out;
 	}
@@ -277,7 +277,7 @@ static int enable_verity(struct file *filp,
 		fsverity_err(inode, "%ps() failed with err %d",
 			     vops->end_enable_verity, err);
 		fsverity_free_info(vi);
-	} else if (WARN_ON(!IS_VERITY(inode))) {
+	} else if (WARN_ON_ONCE(!IS_VERITY(inode))) {
 		err = -EINVAL;
 		fsverity_free_info(vi);
 	} else {

fs/verity/hash_algs.c

@@ -84,9 +84,9 @@ struct fsverity_hash_alg *fsverity_get_hash_alg(const struct inode *inode,
 	}
 
 	err = -EINVAL;
-	if (WARN_ON(alg->digest_size != crypto_ahash_digestsize(tfm)))
+	if (WARN_ON_ONCE(alg->digest_size != crypto_ahash_digestsize(tfm)))
 		goto err_free_tfm;
-	if (WARN_ON(alg->block_size != crypto_ahash_blocksize(tfm)))
+	if (WARN_ON_ONCE(alg->block_size != crypto_ahash_blocksize(tfm)))
 		goto err_free_tfm;
 
 	err = mempool_init_kmalloc_pool(&alg->req_pool, 1,

fs/verity/open.c

@@ -83,7 +83,7 @@ int fsverity_init_merkle_tree_params(struct merkle_tree_params *params,
 	params->log_blocks_per_page = PAGE_SHIFT - log_blocksize;
 	params->blocks_per_page = 1 << params->log_blocks_per_page;
 
-	if (WARN_ON(!is_power_of_2(params->digest_size))) {
+	if (WARN_ON_ONCE(!is_power_of_2(params->digest_size))) {
 		err = -EINVAL;
 		goto out_err;
 	}

include/linux/fsverity.h

@@ -233,18 +233,18 @@ static inline int fsverity_ioctl_read_metadata(struct file *filp,
 static inline bool fsverity_verify_blocks(struct folio *folio, size_t len,
 					  size_t offset)
 {
-	WARN_ON(1);
+	WARN_ON_ONCE(1);
 	return false;
 }
 
 static inline void fsverity_verify_bio(struct bio *bio)
 {
-	WARN_ON(1);
+	WARN_ON_ONCE(1);
 }
 
 static inline void fsverity_enqueue_verify_work(struct work_struct *work)
 {
-	WARN_ON(1);
+	WARN_ON_ONCE(1);
 }
 
 #endif	/* !CONFIG_FS_VERITY */