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| author | Danilo Krummrich <dakr@kernel.org> | 2024-08-13 00:34:35 +0200 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2024-09-04 06:15:37 +0200 |
| commit | 489a744e5fb16503b495ad1fa3dd1abf25b224e7 (patch) | |
| tree | 3bf8daea81e7f162b13f84a6c1a20459d0d5f207 /mm/slab_common.c | |
| parent | mm: krealloc: consider spare memory for __GFP_ZERO (diff) | |
| download | linux-489a744e5fb16503b495ad1fa3dd1abf25b224e7.tar.xz linux-489a744e5fb16503b495ad1fa3dd1abf25b224e7.zip | |
mm: krealloc: clarify valid usage of __GFP_ZERO
Properly document that 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.
Link: https://lkml.kernel.org/r/20240812223707.32049-2-dakr@kernel.org
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/slab_common.c')
| -rw-r--r-- | mm/slab_common.c | 20 |
1 files changed, 18 insertions, 2 deletions
diff --git a/mm/slab_common.c b/mm/slab_common.c index cff602cedf8e..1b380eb3b4f2 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -1301,11 +1301,27 @@ __do_krealloc(const void *p, size_t new_size, gfp_t flags) * @new_size: how many bytes of memory are required. * @flags: the type of memory to allocate. * - * The contents of the object pointed to are preserved up to the - * lesser of the new and old sizes (__GFP_ZERO flag is effectively ignored). * If @p is %NULL, krealloc() behaves exactly like kmalloc(). If @new_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. + * + * This is the case, since krealloc() only knows about the bucket size of an + * allocation (but not the exact size it was allocated with) and hence + * implements the following semantics for shrinking and growing buffers with + * __GFP_ZERO. + * + * new bucket + * 0 size size + * |--------|----------------| + * | keep | zero | + * + * In any case, the contents of the object pointed to are preserved up to the + * lesser of the new and old sizes. + * * Return: pointer to the allocated memory or %NULL in case of error */ void *krealloc_noprof(const void *p, size_t new_size, gfp_t flags) |