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Tue, 2 Jul 2024 21:18:36 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id EKoGNqxuhGauCgAAD6G6ig (envelope-from ); Tue, 02 Jul 2024 21:18:36 +0000 Message-ID: Date: Tue, 2 Jul 2024 23:18:36 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm, slab: extend kmalloc() alignment for non power-of-two sizes Content-Language: en-US To: Alice Ryhl Cc: linux-mm@kvack.org, David Rientjes , Christoph Lameter , Hyeonggon Yoo <42.hyeyoo@gmail.com>, Roman Gushchin , Kees Cook , Boqun Feng , rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org, patches@lists.linux.dev References: <20240702155800.166503-2-vbabka@suse.cz> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSBWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBzdXNlLmN6PsLBlAQTAQoAPgIbAwULCQgHAwUVCgkICwUWAgMBAAIe AQIXgBYhBKlA1DSZLC6OmRA9UCJPp+fMgqZkBQJkBREIBQkRadznAAoJECJPp+fMgqZkNxIQ ALZRqwdUGzqL2aeSavbum/VF/+td+nZfuH0xeWiO2w8mG0+nPd5j9ujYeHcUP1edE7uQrjOC Gs9sm8+W1xYnbClMJTsXiAV88D2btFUdU1mCXURAL9wWZ8Jsmz5ZH2V6AUszvNezsS/VIT87 AmTtj31TLDGwdxaZTSYLwAOOOtyqafOEq+gJB30RxTRE3h3G1zpO7OM9K6ysLdAlwAGYWgJJ V4JqGsQ/lyEtxxFpUCjb5Pztp7cQxhlkil0oBYHkudiG8j1U3DG8iC6rnB4yJaLphKx57NuQ PIY0Bccg+r9gIQ4XeSK2PQhdXdy3UWBr913ZQ9AI2usid3s5vabo4iBvpJNFLgUmxFnr73SJ KsRh/2OBsg1XXF/wRQGBO9vRuJUAbnaIVcmGOUogdBVS9Sun/Sy4GNA++KtFZK95U7J417/J Hub2xV6Ehc7UGW6fIvIQmzJ3zaTEfuriU1P8ayfddrAgZb25JnOW7L1zdYL8rXiezOyYZ8Fm ZyXjzWdO0RpxcUEp6GsJr11Bc4F3aae9OZtwtLL/jxc7y6pUugB00PodgnQ6CMcfR/HjXlae h2VS3zl9+tQWHu6s1R58t5BuMS2FNA58wU/IazImc/ZQA+slDBfhRDGYlExjg19UXWe/gMcl De3P1kxYPgZdGE2eZpRLIbt+rYnqQKy8UxlszsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZAUSmwUJDK5EZgAKCRAiT6fnzIKmZOJGEACOKABgo9wJXsbWhGWYO7mD 8R8mUyJHqbvaz+yTLnvRwfe/VwafFfDMx5GYVYzMY9TWpA8psFTKTUIIQmx2scYsRBUwm5VI EurRWKqENcDRjyo+ol59j0FViYysjQQeobXBDDE31t5SBg++veI6tXfpco/UiKEsDswL1WAr tEAZaruo7254TyH+gydURl2wJuzo/aZ7Y7PpqaODbYv727Dvm5eX64HCyyAH0s6sOCyGF5/p eIhrOn24oBf67KtdAN3H9JoFNUVTYJc1VJU3R1JtVdgwEdr+NEciEfYl0O19VpLE/PZxP4wX PWnhf5WjdoNI1Xec+RcJ5p/pSel0jnvBX8L2cmniYnmI883NhtGZsEWj++wyKiS4NranDFlA HdDM3b4lUth1pTtABKQ1YuTvehj7EfoWD3bv9kuGZGPrAeFNiHPdOT7DaXKeHpW9homgtBxj 8aX/UkSvEGJKUEbFL9cVa5tzyialGkSiZJNkWgeHe+jEcfRT6pJZOJidSCdzvJpbdJmm+eED w9XOLH1IIWh7RURU7G1iOfEfmImFeC3cbbS73LQEFGe1urxvIH5K/7vX+FkNcr9ujwWuPE9b 1C2o4i/yZPLXIVy387EjA6GZMqvQUFuSTs/GeBcv0NjIQi8867H3uLjz+mQy63fAitsDwLmR EP+ylKVEKb0Q2A== In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Action: no action X-Rspamd-Queue-Id: AA7261A0003 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: 37yz3rrjoowi3ffwj9ghiphhjzrcdbpu X-HE-Tag: 1719955118-106385 X-HE-Meta: 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 vlXFEbyE 9WZeO/q/Z3UcyJAtcq5L6HooskRp385/nvT1xnvRxh7xVo9Mj5OsDVATCH67oTHHDFIoTrN6aF8agheqayzEE1nmviaKbGVBswH7mZbiNlXnb2lfY/1THVhbSlDYMBTg8VbZCVUxYveDzaKWJXBo8AnPqS/hs5rP/V4JVkLFdfDPLnMCi1wO9miDvzzlSxwvLRV2RnXAfO3sy6wKwIRC1jbKlqc4maZU0h0GUcRO3izvsVgTvmg1mYysLNynFDEm4ork6F87A8UzjYgZOLyJdmpIIVFQJlex3eOkKASfPJSAZkVoXAi4i0eJIScytKA7LVcjUbm9Y5VsuH6z6ePG6LToptFMq/R7RlH7QVxOBEvfgyeM= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000002, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 7/2/24 6:40 PM, Alice Ryhl wrote: > On Tue, Jul 2, 2024 at 5:58 PM Vlastimil Babka wrote: > Thanks! > > Since this change is motivated by Rust, why not also include the Rust > change in this patch? You would need to remove the if inside > krealloc_aligned in rust/kernel/alloc/allocator.rs and update the > comments. Right, thanks. Does this look ok? (not tested as I don't have the environment working) diff --git a/rust/kernel/alloc/allocator.rs b/rust/kernel/alloc/allocator.rs index 229642960cd1..c619acb8b285 100644 --- a/rust/kernel/alloc/allocator.rs +++ b/rust/kernel/alloc/allocator.rs @@ -18,23 +18,16 @@ pub(crate) unsafe fn krealloc_aligned(ptr: *mut u8, new_layout: Layout, flags: F // Customized layouts from `Layout::from_size_align()` can have size < align, so pad first. let layout = new_layout.pad_to_align(); + // Note that `layout.size()` (after padding) is guaranteed to be a multiple of `layout.align()` + // which together with the slab guarantee means the `krealloc` will return a properly aligned + // object (see comments in `kmalloc()` for more information). let mut size = layout.size(); - if layout.align() > bindings::ARCH_SLAB_MINALIGN { - // The alignment requirement exceeds the slab guarantee, thus try to enlarge the size - // to use the "power-of-two" size/alignment guarantee (see comments in `kmalloc()` for - // more information). - // - // Note that `layout.size()` (after padding) is guaranteed to be a multiple of - // `layout.align()`, so `next_power_of_two` gives enough alignment guarantee. - size = size.next_power_of_two(); - } - // SAFETY: // - `ptr` is either null or a pointer returned from a previous `k{re}alloc()` by the // function safety requirement. // - `size` is greater than 0 since it's either a `layout.size()` (which cannot be zero - // according to the function safety requirement) or a result from `next_power_of_two()`. + // according to the function safety requirement) unsafe { bindings::krealloc(ptr as *const core::ffi::c_void, size, flags.0) as *mut u8 } }