Re: [PATCH v2 2/8] mm: Add kvmalloc_ab_c and kvzalloc_struct

[Joe Perches]

On Wed, 2018-02-14 at 12:11 -0800, Matthew Wilcox wrote:
> From: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>
> 
> We have kvmalloc_array in order to safely allocate an array with a
> number of elements specified by userspace (avoiding arithmetic overflow
> leading to a buffer overrun).  But it's fairly common to have a header
> in front of that array (eg specifying the length of the array), so we
> need a helper function for that situation.
> 
> kvmalloc_ab_c() is the workhorse that does the calculation, but in spite
> of our best efforts to name the arguments, it's really hard to remember
> which order to put the arguments in.  kvzalloc_struct() eliminates that
> effort; you tell it about the struct you're allocating, and it puts the
> arguments in the right order for you (and checks that the arguments
> you've given are at least plausible).
> 
> For comparison between the three schemes:
> 
> 	sev = kvzalloc(sizeof(*sev) + sizeof(struct v4l2_kevent) * elems,
> 			GFP_KERNEL);
> 	sev = kvzalloc_ab_c(elems, sizeof(struct v4l2_kevent), sizeof(*sev),
> 			GFP_KERNEL);
> 	sev = kvzalloc_struct(sev, events, elems, GFP_KERNEL);

Perhaps kv[zm]alloc_buf_and_array is better naming.