Re: [PATCH] initramfs: Reduce hardlink hash allocation sizes

[Jan Kara]

On Sat 19-09-26 23:39:00, Thorsten Blum wrote:
> Each hardlink hash entry reserves N_ALIGN(PATH_MAX) bytes for its name.
> This makes every allocation larger than 4 KiB, placing it in the
> kmalloc-8k bucket even for short names.
> 
> Use a flexible array with the already validated cpio name_len to reduce
> allocation sizes.
> 
> Also use const for the read-only name parameter.
> 
> Signed-off-by: Thorsten Blum <blum@xxxxxxxxxx>

...

> @@ -106,14 +106,15 @@ static char __init *find_link(int major, int minor, int ino,
>  			continue;
>  		return (*p)->name;
>  	}
> -	q = kmalloc_obj(struct hash);
> +
> +	q = kmalloc_flex(struct hash, name, nlen);
>  	if (!q)
>  		panic_show_mem("can't allocate link hash entry");
>  	q->major = major;
>  	q->minor = minor;
>  	q->ino = ino;
>  	q->mode = mode;
> -	strscpy(q->name, name);
> +	strscpy(q->name, name, nlen);
>  	q->next = NULL;
>  	*p = q;
>  	hardlink_seen = true;

What about the space for terminating \0 ? This way the stored 'name' will
be actually one character shorter because strscpy() will overwrite the last
character by \0. Or do I miss something?

								Honza

> @@ -355,7 +356,7 @@ static void __init clean_path(char *path, umode_t fmode)
>  static int __init maybe_link(void)
>  {
>  	if (nlink >= 2) {
> -		char *old = find_link(major, minor, ino, mode, collected);
> +		char *old = find_link(major, minor, ino, mode, collected, name_len);
>  		if (old) {
>  			clean_path(collected, 0);
>  			return (init_link(old, collected) < 0) ? -1 : 1;
-- 
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR