From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2861B18CBF8 for ; Tue, 30 Jul 2024 19:42:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722368543; cv=none; b=hztZVhXl7o6pgFg7ttZe8Ebewa3uP/3fu+P8DeVimf1kT/5CKiwCw0GEl9utZ3M8iV+WclUN+e1Nvacrf3No6ARRsr+dz3hhGKqObj0/k7bPF9D2EJ1mHAQhJzXYu9cl9B8Q3jY/5DhfL1LBL8OdrfRq2ny1UbOE6oVn807cNUI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722368543; c=relaxed/simple; bh=M76h9UGEvDOvQR6+2Hn3EAWaBbezIN4frYXV3T3puu8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=i2aZVAifh1JSgKV+ZhAEUAHAbQLVpfSWiVnAy/RdPr2FxDYLhzfjQqZrC60T4V0FaBNTvPJeWgFKXEdD4mTJYybpWae4l/U2D9C7kPOuV5b6A75n2Yi7FBhHzvYeykdlGlvbz0RdzTAERx42fjZ2RsYJvnePKR1L/HSf4eEF5SA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Hz3I3PPg; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Hz3I3PPg" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5FA1AC4AF0A; Tue, 30 Jul 2024 19:42:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1722368542; bh=M76h9UGEvDOvQR6+2Hn3EAWaBbezIN4frYXV3T3puu8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Hz3I3PPgpwhw3lVSMpgtM9ztVA3tbfI3MKtbxzj+0dqVYZnDDiwozDj8zEop394Cg Lo4e9zEyKWlHpuwes3fvlngGhlKbyJ3hEfxUckaBRS8L4XYmHhfNGkGrHH4LwRFp2d gmSUg53aPKuRhlU2exxn36PshWOinMgX2bl3ZpmINY16Two2v7FM5XcCx7ZuG6yqX/ t7DVl5p2nTwixIb9yqcJSqSlsM8NlCBn8hPAzkCGpqgAD39qhx/7JPa8R3zbLAdF3e 8F+baNJp21sb5CKXM0Ya0JuaXP5kaEj7OWUc7KsCsbju0tjkN4OsaAYA3D8bOUJ57y Pt0i6ic5OCsEQ== From: Danilo Krummrich To: akpm@linux-foundation.org, cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, vbabka@suse.cz, roman.gushchin@linux.dev, 42.hyeyoo@gmail.com Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Danilo Krummrich Subject: [PATCH 2/2] mm: krealloc: clarify valid usage of __GFP_ZERO Date: Tue, 30 Jul 2024 21:42:06 +0200 Message-ID: <20240730194214.31483-2-dakr@kernel.org> X-Mailer: git-send-email 2.45.2 In-Reply-To: <20240730194214.31483-1-dakr@kernel.org> References: <20240730194214.31483-1-dakr@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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. Signed-off-by: Danilo Krummrich --- include/linux/slab.h | 8 ++++++++ mm/slab_common.c | 10 ++++++++-- 2 files changed, 16 insertions(+), 2 deletions(-) diff --git a/include/linux/slab.h b/include/linux/slab.h index c9cb42203183..26f14c04000a 100644 --- a/include/linux/slab.h +++ b/include/linux/slab.h @@ -733,6 +733,14 @@ static inline __alloc_size(1, 2) void *kmalloc_array_noprof(size_t n, size_t siz * @new_n: new number of elements to alloc * @new_size: new size of a single member of the array * @flags: the type of memory to allocate (see kmalloc) + * + * 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. */ static inline __realloc_size(2, 3) void * __must_check krealloc_array_noprof(void *p, size_t new_n, diff --git a/mm/slab_common.c b/mm/slab_common.c index cff602cedf8e..faa13f42b111 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -1301,11 +1301,17 @@ __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. + * + * 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) -- 2.45.2