ext4: hash: change kzalloc(n * sizeof, ...) to kcalloc(n, sizeof, ...)

[PATCH] ext4: hash: change kzalloc(n * sizeof, ...) to kcalloc(n, sizeof, ...)

Posted by Ethan Carter Edwards 9 months ago

Open coded arithmetic in allocator arguments is discouraged. Helper
functions like kcalloc are preferred.

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments

Signed-off-by: Ethan Carter Edwards <ethan@ethancedwards.com>
---
 fs/ext4/hash.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ext4/hash.c b/fs/ext4/hash.c
index deabe29da7fbc3d35f674ff861a2f3b579ffdea2..7a9afac1597c69f319f02bb816ca797d32c188ca 100644
--- a/fs/ext4/hash.c
+++ b/fs/ext4/hash.c
@@ -302,7 +302,7 @@ int ext4fs_dirhash(const struct inode *dir, const char *name, int len,
 
 	if (len && IS_CASEFOLDED(dir) &&
 	   (!IS_ENCRYPTED(dir) || fscrypt_has_encryption_key(dir))) {
-		buff = kzalloc(sizeof(char) * PATH_MAX, GFP_KERNEL);
+		buff = kcalloc(PATH_MAX, sizeof(char), GFP_KERNEL);
 		if (!buff)
 			return -ENOMEM;
 

---
base-commit: da920b7df701770e006928053672147075587fb2
change-id: 20250315-ext4-hash-kcalloc-203033977bd9

Best regards,
-- 
Ethan Carter Edwards <ethan@ethancedwards.com>

Re: [PATCH] ext4: hash: change kzalloc(n * sizeof, ...) to kcalloc(n, sizeof, ...)

Posted by Matthew Wilcox 9 months ago

On Sat, Mar 15, 2025 at 12:29:34PM -0400, Ethan Carter Edwards wrote:
> Open coded arithmetic in allocator arguments is discouraged. Helper
> functions like kcalloc are preferred.

Well, yes, but ...

> +++ b/fs/ext4/hash.c
> @@ -302,7 +302,7 @@ int ext4fs_dirhash(const struct inode *dir, const char *name, int len,
>  
>  	if (len && IS_CASEFOLDED(dir) &&
>  	   (!IS_ENCRYPTED(dir) || fscrypt_has_encryption_key(dir))) {
> -		buff = kzalloc(sizeof(char) * PATH_MAX, GFP_KERNEL);
> +		buff = kcalloc(PATH_MAX, sizeof(char), GFP_KERNEL);

sizeof(char) is defined to be 1.  So this should just be
kzalloc(PATH_MAX, GFP_KERNEL).

Re: [PATCH] ext4: hash: change kzalloc(n * sizeof, ...) to kcalloc(n, sizeof, ...)

Posted by Andreas Dilger 9 months ago

On Mar 15, 2025, at 9:28 PM, Matthew Wilcox <willy@infradead.org> wrote:
> 
> On Sat, Mar 15, 2025 at 12:29:34PM -0400, Ethan Carter Edwards wrote:
>> Open coded arithmetic in allocator arguments is discouraged. Helper
>> functions like kcalloc are preferred.
> 
> Well, yes, but ...
> 
>> +++ b/fs/ext4/hash.c
>> @@ -302,7 +302,7 @@ int ext4fs_dirhash(const struct inode *dir, const char *name, int len,
>> 
>> 	if (len && IS_CASEFOLDED(dir) &&
>> 	   (!IS_ENCRYPTED(dir) || fscrypt_has_encryption_key(dir))) {
>> -		buff = kzalloc(sizeof(char) * PATH_MAX, GFP_KERNEL);
>> +		buff = kcalloc(PATH_MAX, sizeof(char), GFP_KERNEL);
> 
> sizeof(char) is defined to be 1.  So this should just be
> kzalloc(PATH_MAX, GFP_KERNEL).

I was going to say exactly the same thing.
Passing "1" to kcalloc() is just pure overhead.

Cheers, Andreas