From 3ddc2fefe6f34ec870fcb22f4cd656e53db079f2 Mon Sep 17 00:00:00 2001 From: Danilo Krummrich Date: Mon, 22 Jul 2024 18:29:23 +0200 Subject: mm: vmalloc: implement vrealloc() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Patch series "Align kvrealloc() with krealloc()", v2. Besides the obvious (and desired) difference between krealloc() and kvrealloc(), there is some inconsistency in their function signatures and behavior: - krealloc() frees the memory when the requested size is zero, whereas kvrealloc() simply returns a pointer to the existing allocation. - krealloc() behaves like kmalloc() if a NULL pointer is passed, whereas kvrealloc() does not accept a NULL pointer at all and, if passed, would fault instead. - krealloc() is self-contained, whereas kvrealloc() relies on the caller to provide the size of the previous allocation. Inconsistent behavior throughout allocation APIs is error prone, hence make kvrealloc() behave like krealloc(), which seems superior in all mentioned aspects. In order to be able to get rid of kvrealloc()'s oldsize parameter, introduce vrealloc() and make use of it in kvrealloc(). Making use of vrealloc() in kvrealloc() also provides oppertunities to grow (and shrink) allocations more efficiently. For instance, vrealloc() can be optimized to allocate and map additional pages to grow the allocation or unmap and free unused pages to shrink the allocation. Besides the above, those functions are required by Rust's allocator abstractons [1] (rework based on this series in [2]). With `Vec` or `KVec` respectively, potentially growing (and shrinking) data structures are rather common. [1] https://lore.kernel.org/lkml/20240704170738.3621-1-dakr@redhat.com/ [2] https://git.kernel.org/pub/scm/linux/kernel/git/dakr/linux.git/log/?h=rust/mm This patch (of 2): Implement vrealloc() analogous to krealloc(). Currently, krealloc() requires the caller to pass the size of the previous memory allocation, which, instead, should be self-contained. We attempt to fix this in a subsequent patch which, in order to do so, requires vrealloc(). Besides that, we need realloc() functions for kernel allocators in Rust too. With `Vec` or `KVec` respectively, potentially growing (and shrinking) data structures are rather common. [dakr@kernel.org: fix missing nommu implementation] Link: https://lkml.kernel.org/r/20240725141227.13954-1-dakr@kernel.org [dakr@kernel.org: document concurrency restrictions] Link: https://lkml.kernel.org/r/20240725125442.4957-1-dakr@kernel.org [dakr@kernel.org: consider spare memory for __GFP_ZERO] Link: https://lkml.kernel.org/r/20240730185049.6244-3-dakr@kernel.org [dakr@kernel.org: properly document __GFP_ZERO behavior] Link: https://lkml.kernel.org/r/20240730185049.6244-4-dakr@kernel.org Link: https://lkml.kernel.org/r/20240722163111.4766-1-dakr@kernel.org Link: https://lkml.kernel.org/r/20240722163111.4766-2-dakr@kernel.org Signed-off-by: Danilo Krummrich Acked-by: Michal Hocko Acked-by: Vlastimil Babka Cc: Chandan Babu R Cc: Christian König Cc: Christoph Hellwig Cc: Christoph Lameter Cc: David Rientjes Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com> Cc: Joonsoo Kim Cc: Kees Cook Cc: Marc Zyngier Cc: Michael Ellerman Cc: Miguel Ojeda Cc: Oliver Upton Cc: Pekka Enberg Cc: Roman Gushchin Cc: Uladzislau Rezki Cc: Wedson Almeida Filho Signed-off-by: Andrew Morton --- include/linux/vmalloc.h | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'include') diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h index e4a631ec430b..ad2ce7a6ab7a 100644 --- a/include/linux/vmalloc.h +++ b/include/linux/vmalloc.h @@ -189,6 +189,10 @@ extern void *__vcalloc_noprof(size_t n, size_t size, gfp_t flags) __alloc_size(1 extern void *vcalloc_noprof(size_t n, size_t size) __alloc_size(1, 2); #define vcalloc(...) alloc_hooks(vcalloc_noprof(__VA_ARGS__)) +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__)) + extern void vfree(const void *addr); extern void vfree_atomic(const void *addr); -- cgit v1.2.3