Date: Wed, 14 Feb 2018 13:29:37 -0800 From: Matthew Wilcox <willy@...radead.org> To: Joe Perches <joe@...ches.com> Cc: Andrew Morton <akpm@...ux-foundation.org>, Matthew Wilcox <mawilcox@...rosoft.com>, linux-mm@...ck.org, Kees Cook <keescook@...omium.org>, linux-kernel@...r.kernel.org, kernel-hardening@...ts.openwall.com Subject: Re: [PATCH v2 2/8] mm: Add kvmalloc_ab_c and kvzalloc_struct On Wed, Feb 14, 2018 at 01:24:09PM -0800, Joe Perches wrote: > On Wed, 2018-02-14 at 13:12 -0800, Matthew Wilcox wrote: > > On Wed, Feb 14, 2018 at 12:45:52PM -0800, Joe Perches wrote: > > > Perhaps kv[zm]alloc_buf_and_array is better naming. > > > > I think that's actively misleading. The programmer isn't allocating a > > buf, they're allocating a struct. kvzalloc_hdr_arr was the earlier name, > > and that made some sense; they're allocating an array with a header. > > But nobody thinks about it like that; they're allocating a structure > > with a variably sized array at the end of it. > > > > If C macros had decent introspection, I'd like it to be: > > > > sev = kvzalloc_struct(elems, GFP_KERNEL); > > > > and have the macro examine the structure pointed to by 'sev', check > > the last element was an array, calculate the size of the array element, > > and call kvzalloc_ab_c. But we don't live in that world, so I have to > > get the programmer to tell me the structure and the name of the last > > element in it. > > Look at your patch 4 > > - dev_dax = kzalloc(sizeof(*dev_dax) + sizeof(*res) * count, GFP_KERNEL); > + dev_dax = kvzalloc_struct(dev_dax, res, count, GFP_KERNEL); > > Here what is being allocated is exactly a struct > and an array. No, it's a struct *containing* an array. Look at patches 5 & 8 where I have to convert the structs to contain the array which was silently being allocated immediately after them. > And this doesn't compile either. Does for me. What error are you seeing?
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