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Date:   Mon, 7 Nov 2022 19:41:05 +0900
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To:     Kees Cook <keescook@chromium.org>
Cc:     Vlastimil Babka <vbabka@suse.cz>, Jonathan Corbet <corbet@lwn.net>,
        Akira Yokosawa <akiyks@gmail.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
From:   Akira Yokosawa <akiyks@gmail.com>
Subject: Duplicate kernel-doc comments for ksize()
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Hi Kees,

"make htmldocs" reports duplicate C declaration of ksize()
as follows:

/linux/Documentation/core-api/mm-api:43: ./mm/slab_common.c:1428: WARNING: Duplicate C declaration, also defined at core-api/mm-api:212.
Declaration is '.. c:function:: size_t ksize (const void *objp)'.

This is due to the kernel-doc comment for ksize() added in
include/linux/slab.h by a commit you have authored:
  05a940656e1e ("slab:Introduce kmalloc_size_roundup()").

/**
 * ksize - Report actual allocation size of associated object
 *
 * @objp: Pointer returned from a prior kmalloc()-family allocation.
 *
 * This should not be used for writing beyond the originally requested
 * allocation size. Either use krealloc() or round up the allocation size
 * with kmalloc_size_roundup() prior to allocation. If this is used to
 * access beyond the originally requested allocation size, UBSAN_BOUNDS
 * and/or FORTIFY_SOURCE may trip, since they only know about the
 * originally allocated size via the __alloc_size attribute.
 */

There is another kernel-doc comment in mm/slab_common.c (originally
by Manfred, since v2.6.14):

/**
 * ksize - get the actual amount of memory allocated for a given object
 * @objp: Pointer to the object
 *
 * kmalloc may internally round up allocations and return more memory
 * than requested. ksize() can be used to determine the actual amount of
 * memory allocated. The caller may use this additional memory, even though
 * a smaller amount of memory was initially specified with the kmalloc call.
 * The caller must guarantee that objp points to a valid object previously
 * allocated with either kmalloc() or kmem_cache_alloc(). The object
 * must not be freed during the duration of the call.
 *
 * Return: size of the actual memory used by @objp in bytes
 */

I guess the one in slab_common.c is outdated and can be removed.
Can you please take care of it?

        Thanks, Akira