diff options
author | Danilo Krummrich <dakr@kernel.org> | 2024-07-17 16:59:23 +0200 |
---|---|---|
committer | Danilo Krummrich <dakr@kernel.org> | 2024-08-13 16:04:19 +0200 |
commit | 590728e3eb28171682aece2cf1d6209024085271 (patch) | |
tree | 4f373c98699a8d47a2fb076e101e888f90ea444e /mm | |
parent | b54176537b79224f4591018610015aab700853ad (diff) |
mm: vmalloc: implement vrealloc()
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` potentially growing (and shrinking) data structures are
rather common.
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Diffstat (limited to 'mm')
-rw-r--r-- | mm/nommu.c | 5 | ||||
-rw-r--r-- | mm/vmalloc.c | 70 |
2 files changed, 75 insertions, 0 deletions
diff --git a/mm/nommu.c b/mm/nommu.c index 7296e775e04e..40cac1348b40 100644 --- a/mm/nommu.c +++ b/mm/nommu.c @@ -126,6 +126,11 @@ void *__vmalloc_noprof(unsigned long size, gfp_t gfp_mask) } EXPORT_SYMBOL(__vmalloc_noprof); +void *vrealloc_noprof(const void *p, size_t size, gfp_t flags) +{ + return krealloc_noprof(p, size, (flags | __GFP_COMP) & ~__GFP_HIGHMEM); +} + void *__vmalloc_node_range_noprof(unsigned long size, unsigned long align, unsigned long start, unsigned long end, gfp_t gfp_mask, pgprot_t prot, unsigned long vm_flags, int node, diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 6b783baf12a1..48cc10dd06c0 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -4037,6 +4037,76 @@ void *vzalloc_node_noprof(unsigned long size, int node) } EXPORT_SYMBOL(vzalloc_node_noprof); +/** + * vrealloc - reallocate virtually contiguous memory; contents remain unchanged + * @p: object to reallocate memory for + * @size: the size to reallocate + * @flags: the flags for the page level allocator + * + * If @p is %NULL, vrealloc() behaves exactly like vmalloc(). If @size is 0 and + * @p is not a %NULL pointer, the object pointed to is freed. + * + * If __GFP_ZERO logic is requested, callers must ensure that, starting with the + * initial memory allocation, every subsequent call to this API for the same + * memory allocation is flagged with __GFP_ZERO. Otherwise, it is possible that + * __GFP_ZERO is not fully honored by this API. + * + * In any case, the contents of the object pointed to are preserved up to the + * lesser of the new and old sizes. + * + * This function must not be called concurrently with itself or vfree() for the + * same memory allocation. + * + * 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) +{ + size_t old_size = 0; + void *n; + + if (!size) { + vfree(p); + return NULL; + } + + if (p) { + struct vm_struct *vm; + + vm = find_vm_area(p); + if (unlikely(!vm)) { + WARN(1, "Trying to vrealloc() nonexistent vm area (%p)\n", p); + return NULL; + } + + old_size = get_vm_area_size(vm); + } + + /* + * 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 spare memory. */ + if (want_init_on_alloc(flags)) + memset((void *)p + size, 0, old_size - size); + + return (void *)p; + } + + /* TODO: Grow the vm_area, i.e. allocate and map additional pages. */ + n = __vmalloc_noprof(size, flags); + if (!n) + return NULL; + + if (p) { + memcpy(n, p, old_size); + vfree(p); + } + + return n; +} + #if defined(CONFIG_64BIT) && defined(CONFIG_ZONE_DMA32) #define GFP_VMALLOC32 (GFP_DMA32 | GFP_KERNEL) #elif defined(CONFIG_64BIT) && defined(CONFIG_ZONE_DMA) |