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Message-ID: <aHdOfv1QyisOiAXL@pc636>
Date: Wed, 16 Jul 2025 09:02:22 +0200
From: Uladzislau Rezki <urezki@...il.com>
To: Hui Zhu <hui.zhu@...ux.dev>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Uladzislau Rezki <urezki@...il.com>,
Miguel Ojeda <ojeda@...nel.org>,
Alex Gaynor <alex.gaynor@...il.com>,
Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
bjorn3_gh@...tonmail.com, Benno Lossin <lossin@...nel.org>,
Andreas Hindborg <a.hindborg@...nel.org>,
Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>,
Danilo Krummrich <dakr@...nel.org>,
Geliang Tang <geliang@...nel.org>, Hui Zhu <zhuhui@...inos.cn>,
linux-kernel@...r.kernel.org, linux-mm@...ck.org,
rust-for-linux@...r.kernel.org
Subject: Re: [PATCH 1/3] vmalloc: Add vrealloc_align to support allocation of
aligned vmap pages
On Tue, Jul 15, 2025 at 05:59:46PM +0800, Hui Zhu wrote:
> From: Hui Zhu <zhuhui@...inos.cn>
>
> This commit add new function vrealloc_align.
> vrealloc_align support allocation of aligned vmap pages with
> __vmalloc_node_noprof.
> And vrealloc_align will check the old address. If this address does
> not meet the current alignment requirements, it will also release
> the old vmap pages and reallocate new vmap pages that satisfy the
> alignment requirements.
>
> Co-developed-by: Geliang Tang <geliang@...nel.org>
> Signed-off-by: Geliang Tang <geliang@...nel.org>
> Signed-off-by: Hui Zhu <zhuhui@...inos.cn>
> ---
> include/linux/vmalloc.h | 5 +++
> mm/vmalloc.c | 80 ++++++++++++++++++++++++++---------------
> 2 files changed, 57 insertions(+), 28 deletions(-)
>
> diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
> index fdc9aeb74a44..0ce0c1ea2427 100644
> --- a/include/linux/vmalloc.h
> +++ b/include/linux/vmalloc.h
> @@ -201,6 +201,11 @@ void * __must_check vrealloc_noprof(const void *p, size_t size, gfp_t flags)
> __realloc_size(2);
> #define vrealloc(...) alloc_hooks(vrealloc_noprof(__VA_ARGS__))
>
> +void * __must_check vrealloc_align_noprof(const void *p, size_t size,
> + size_t align, gfp_t flags)
> + __realloc_size(2);
> +#define vrealloc_align(...) alloc_hooks(vrealloc_align_noprof(__VA_ARGS__))
> +
> extern void vfree(const void *addr);
> extern void vfree_atomic(const void *addr);
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index ab986dd09b6a..41cb3603b3cc 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -4081,9 +4081,11 @@ void *vzalloc_node_noprof(unsigned long size, int node)
> EXPORT_SYMBOL(vzalloc_node_noprof);
>
> /**
> - * vrealloc - reallocate virtually contiguous memory; contents remain unchanged
> + * vrealloc_align - reallocate virtually contiguous memory;
> + * contents remain unchanged
> * @p: object to reallocate memory for
> * @size: the size to reallocate
> + * @align: requested alignment
> * @flags: the flags for the page level allocator
> *
> * If @p is %NULL, vrealloc() behaves exactly like vmalloc(). If @size is 0 and
> @@ -4103,7 +4105,8 @@ EXPORT_SYMBOL(vzalloc_node_noprof);
> * Return: pointer to the allocated memory; %NULL if @size is zero or in case of
> * failure
> */
> -void *vrealloc_noprof(const void *p, size_t size, gfp_t flags)
> +void *vrealloc_align_noprof(const void *p, size_t size, size_t align,
> + gfp_t flags)
> {
> struct vm_struct *vm = NULL;
> size_t alloced_size = 0;
> @@ -4116,49 +4119,65 @@ void *vrealloc_noprof(const void *p, size_t size, gfp_t flags)
> }
>
> if (p) {
> + if (!is_power_of_2(align)) {
> + WARN(1, "Trying to vrealloc_align() align is not power of 2 (%ld)\n",
> + align);
> + return NULL;
> + }
> +
> vm = find_vm_area(p);
> if (unlikely(!vm)) {
> - WARN(1, "Trying to vrealloc() nonexistent vm area (%p)\n", p);
> + WARN(1, "Trying to vrealloc_align() nonexistent vm area (%p)\n", p);
> return NULL;
> }
>
> alloced_size = get_vm_area_size(vm);
> old_size = vm->requested_size;
> if (WARN(alloced_size < old_size,
> - "vrealloc() has mismatched area vs requested sizes (%p)\n", p))
> + "vrealloc_align() has mismatched area vs requested sizes (%p)\n", p))
> return NULL;
> }
>
> - /*
> - * TODO: Shrink the vm_area, i.e. unmap and free unused pages. What
> - * would be a good heuristic for when to shrink the vm_area?
> - */
> - if (size <= old_size) {
> - /* Zero out "freed" memory, potentially for future realloc. */
> - if (want_init_on_free() || want_init_on_alloc(flags))
> - memset((void *)p + size, 0, old_size - size);
> - vm->requested_size = size;
> - kasan_poison_vmalloc(p + size, old_size - size);
> - return (void *)p;
> - }
> + if (IS_ALIGNED((unsigned long)p, align)) {
> + /*
> + * TODO: Shrink the vm_area, i.e. unmap and free unused pages. What
> + * would be a good heuristic for when to shrink the vm_area?
> + */
> + if (size <= old_size) {
> + /* Zero out "freed" memory, potentially for future realloc. */
> + if (want_init_on_free() || want_init_on_alloc(flags))
> + memset((void *)p + size, 0, old_size - size);
> + vm->requested_size = size;
> + kasan_poison_vmalloc(p + size, old_size - size);
> + return (void *)p;
> + }
>
> - /*
> - * We already have the bytes available in the allocation; use them.
> - */
> - if (size <= alloced_size) {
> - kasan_unpoison_vmalloc(p + old_size, size - old_size,
> - KASAN_VMALLOC_PROT_NORMAL);
> /*
> - * No need to zero memory here, as unused memory will have
> - * already been zeroed at initial allocation time or during
> - * realloc shrink time.
> + * We already have the bytes available in the allocation; use them.
> + */
> + if (size <= alloced_size) {
> + kasan_unpoison_vmalloc(p + old_size, size - old_size,
> + KASAN_VMALLOC_PROT_NORMAL);
> + /*
> + * No need to zero memory here, as unused memory will have
> + * already been zeroed at initial allocation time or during
> + * realloc shrink time.
> + */
> + vm->requested_size = size;
> + return (void *)p;
> + }
> + } else {
> + /*
> + * p is not aligned with align.
> + * Allocate a new address to handle it.
> */
> - vm->requested_size = size;
> - return (void *)p;
> + if (size < old_size)
> + old_size = size;
> }
>
> /* TODO: Grow the vm_area, i.e. allocate and map additional pages. */
> - n = __vmalloc_noprof(size, flags);
> + n = __vmalloc_node_noprof(size, align, flags, NUMA_NO_NODE,
> + __builtin_return_address(0));
> if (!n)
> return NULL;
>
> @@ -4170,6 +4189,11 @@ void *vrealloc_noprof(const void *p, size_t size, gfp_t flags)
> return n;
> }
>
> +void *vrealloc_noprof(const void *p, size_t size, gfp_t flags)
> +{
> + return vrealloc_align_noprof(p, size, 1, flags);
> +}
> +
> #if defined(CONFIG_64BIT) && defined(CONFIG_ZONE_DMA32)
> #define GFP_VMALLOC32 (GFP_DMA32 | GFP_KERNEL)
> #elif defined(CONFIG_64BIT) && defined(CONFIG_ZONE_DMA)
> --
> 2.43.0
>
This is similar what Vitaly is doing. There is already v14
but as example see it here: https://lkml.org/lkml/2025/7/9/1583
--
Uladzislau Rezki
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