From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 4066B470425; Wed, 22 Jul 2026 07:37:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784705873; cv=none; b=PXKHK4B+OV/jzHQVGfW7sz51zHuWPjS/38J3rp8SfzbBj4JWBh8mmpTLLnBBg2ruZ2iO6Uoi5SnF5H9qA0Nrm0JDKadx1e2E8HlNvODjfukepNrtxzemBwcHXor03zZ4OO9fyeq6NNAbldepZLaWeVmmGpFYn9HTjMnCDOo603M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784705873; c=relaxed/simple; bh=jxHPHB6zGDbgs+iMUPDYnEznxe4JaVn0wD5buOWRNyA=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=NPBFmT8cAutvyitdsMQ4SvOO1oB0OaWUsgQpbCTKVaHDXhlQRwxdciqhJpoD6IzM94U/hk7l1F/xgkJNOaUlP1WseXtL+/TraAbZ11wN8DEmSS65DYv9dRqpZ+QBr7T569nYsloEtQyarT+9nd9oOyiYbIhttINdGVUad5erDto= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=NQPR/Ee9; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="NQPR/Ee9" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 82C8E1F000E9; Wed, 22 Jul 2026 07:37:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784705871; bh=U24GCfx2sgqLq5bIDDPFPYQnyCbGgMLuGoPpBXhl0dk=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=NQPR/Ee9a/6x9OQoqQYgsY4+nFDaOU/m18i16EdM4lqTrXI7F7ir8OFmMjrqH4DaL ZLjByXVxvsQRyR6FbQVUSqsGL4Y2yUXe61fW3snJuAzJEd87C+zNiqNxaVKz9YwBFR NGpz7tf5rYELlzxNg9+D7vO2IZ2asvbZFt34xKoX+hFJg2od3mf98ZNYWXCVDV2vOZ Hrf24Yp4D9DIsizRzUVYgV20CXxcAcubvKE3q7ku622J/ypqFAYRvzsa7G4lA7ZdeW 7BNF+KPCPy3rpVlCe+Qx1Yx1bKLEFblduv9O09NeWGV9mMIHa72uzGuu3O5SGLkJt7 D5RnxLCiI2aOQ== Message-ID: Date: Wed, 22 Jul 2026 09:37:43 +0200 Precedence: bulk X-Mailing-List: rcu@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH slab/for-next v4 2/8] mm/slab: handle the !allow_spin case in kfree_rcu_sheaf() To: Harry Yoo , Andrew Morton , Hao Li , Christoph Lameter , David Rientjes , Roman Gushchin , Alexei Starovoitov , Andrii Nakryiko , Puranjay Mohan , Amery Hung , Sebastian Andrzej Siewior , Clark Williams , Steven Rostedt , "Paul E. McKenney" , Frederic Weisbecker , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Boqun Feng , Uladzislau Rezki , Mathieu Desnoyers , Lai Jiangshan , Zqiang , Pedro Falcato , Suren Baghdasaryan , Shengming Hu Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev, rcu@vger.kernel.org, bpf@vger.kernel.org References: <20260720-kfree_rcu_nolock-v4-0-964e03c41a4e@kernel.org> <20260720-kfree_rcu_nolock-v4-2-964e03c41a4e@kernel.org> <1d0d8021-62d2-4c42-a2a6-a7e8ce2f5d37@kernel.org> <0ce88f37-f231-4a00-b06b-95b0910c2db0@kernel.org> From: "Vlastimil Babka (SUSE)" Content-Language: en-US Autocrypt: addr=vbabka@kernel.org; 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 BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSNWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBrZXJuZWwub3JnPsLBsAQTAQoAWhYhBKlA1DSZLC6OmRA9UCJPp+fM gqZkBQJqFFy6GxSAAAAAAAQADm1hbnUyLDIuNSsxLjEyLDIsMgIbAwUJGtCBUAULCQgHAwUV CgkICwUWAgMBAAIeBQIXgAAKCRAiT6fnzIKmZJIUEADFx/tREzUImHrEwVHeSvDFmA7tJysI UVrlvrM09E7GIuzphzv7jYmo8n3ANpCczLEVr4G0syYQdTigaZgv3+FQDIIzhKih1IHhu1Ei XHlywNWKnQxxQEUNi5Mwx43wQz5XVw9F1A7gtKBKNtfogO511hAbrzagrYajyQacEJ/+sfhZ 9Da8ltHIXD8pcYaHUfQgEusCgmEd9+KrUwrTbckFKmYq5chuE6yJ4J0EmWknL096jIE6CnzF FRslQ3B1UKDjxVsm1ZHfir5NeWszLkTvGFsddFaWTgh8UycESG6VQzKXjjewXu2pG7YQYRpj QKm1W5X2TkwWkXRBZTmfmbhxIUMh3+zf5wQ463rSmDN/8v81tdqBtAW6rH/kzg1GvkaTHXn0 507yEHFzBksk2viAuIxxr7km8+/KARYLIdGtx30EG8cKzAUZOK6WqxtNCsXUJNrVE8CWrCaD icoNu7Fs1c5hmPHdSTnU48ce67449DdnO4neLSNhRiGlMHJgfJUmgrxu/hcYeOZ3haWmEQ2w uW1Mh01OHi8QZHCEyAbABrPs9GUgccc/4eYXX9hIgxfSkYzn8f+8NuIFPWl/0uTvjgqU29FQ SbzOLxHq9439Ox40G5mS5eZXRGxITYR+6TXvRGI6P/264jvflnr/pDGUttaikU+0W+1uxgKH cmYbEc7ATQRbGTU1AQgAn0H6UrFiWcovkh6EXVcl+SeqyO6JHOPm+e9Wu0Vw+VIUvXZVUVVQ La1PQDUi6j00ChlcR66g9/V0sPIcSutacPKfdKYOBvzd4rlhL8rfrdEsQw5ApZxrA8kYZVMh FmBRKAa6wos25moTlMKpCWzTH84+WO5+ziCTsTUZASAToz3RdunTD+vQcHj0GqNTPAHK63sf bAB2I0BslZkXkY1RLb/YhuA6E7JyEd2pilZOrIuBGl/5q2qSakgnAVFWFBR/DO27JuAksYnq +aH8vI0xGvwn75KqSk4UzAkDzWSmO4ZHuahKtQgZNsMYV+PGayRBX9b9zbldzopoLBdqHc4n jQARAQABwsF8BBgBCgAmAhsMFiEEqUDUNJksLo6ZED1QIk+n58yCpmQFAmfIHFQFCRYU6J8A CgkQIk+n58yCpmS2PA//bqN1LfcotmArgElsa+0EGZSQlYgK48pm8WAeTXTngudP9IJ4SuKY HR5RNjHcBeqN+Me0zxRqYzRb8nGanHEkDyf4Im8DQM8d6vbyU+FcPmG4skud4kgS1zMHnlVd SXfSIwKC/hKgdHG8aBV7545Lz9X6Iohea+94wneD0aw/hqF+QWewGZhWJriWAZtvEkzNjQOi 4U9F/trLten/x7bpphDSnDMKJtITbtzATT1Dq7o7VpIUK1nCTQALMuMjKCdi8OdU/+V+R3O4 0PXWvX8qrvqYapVbZ+9KqT74FsuB0Ya9uXwgBF2Q6cRuETZk5vqaqKxzqoQZCO8AOz/58j6O 2RHNy/mZEN+7tJ5Tsq42zVJ4jxsT8b9YplavCMsnBgDeRWhcbYhCyttoL7nYISyWg4kQYZ/P wIV3OuNv2f8iKYsxNsRuClOAF82+gvqOy1/1pprFjy8uo2pkoOrb63aOP3vO5VHnRKgra6dq NcaZ+c6J4H+nEJGi2SkHAUJz5oBzuThvPudLvPA/SK8sKoM01IRxSihev/S/5WLazXB1PGem OCbvzC1IjWJJraxiDJ5IygokapUa2RP7+WBR22skQ3SSl6G107QgWKSyTOGWEaRmV53vxQLV jXuCmzSSasTL60zq5yGrT4/DYQVSNEUiUbG4pYekxJujNeEDkUlky0Y= In-Reply-To: <0ce88f37-f231-4a00-b06b-95b0910c2db0@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/22/26 09:28, Harry Yoo wrote: >> Nits below: >> >>> --- >>> mm/slab.h | 18 +++++++++++++++++- >>> mm/slab_common.c | 2 +- >>> mm/slub.c | 36 ++++++++++++++++++++++++++++-------- >>> 3 files changed, 46 insertions(+), 10 deletions(-) >>> >>> diff --git a/mm/slab.h b/mm/slab.h >>> index 281a65233795..85ef2ebc9812 100644 >>> --- a/mm/slab.h >>> +++ b/mm/slab.h >>> @@ -429,7 +445,7 @@ static inline bool is_kmalloc_normal(struct kmem_cache *s) >>> return !(s->flags & (SLAB_CACHE_DMA|SLAB_ACCOUNT|SLAB_RECLAIM_ACCOUNT)); >>> } >>> >>> -bool __kfree_rcu_sheaf(struct kmem_cache *s, void *obj); >>> +bool __kfree_rcu_sheaf(struct kmem_cache *s, void *obj, unsigned int free_flags); >>> void flush_all_rcu_sheaves(void); >>> void flush_rcu_sheaves_on_cache(struct kmem_cache *s); >>> >>> diff --git a/mm/slab_common.c b/mm/slab_common.c >>> index b6426d7ceec9..e07b4e6d6679 100644 >>> --- a/mm/slab_common.c >>> +++ b/mm/slab_common.c >>> @@ -1605,7 +1605,7 @@ static bool kfree_rcu_sheaf(void *obj) >>> >>> s = slab->slab_cache; >>> if (likely(!IS_ENABLED(CONFIG_NUMA) || slab_nid(slab) == numa_mem_id())) >>> - return __kfree_rcu_sheaf(s, obj); >>> + return __kfree_rcu_sheaf(s, obj, SLAB_FREE_DEFAULT); >>> >>> return false; >>> } >>> diff --git a/mm/slub.c b/mm/slub.c >>> index e32a68677537..0c350274fbff 100644 >>> --- a/mm/slub.c >>> +++ b/mm/slub.c >>> @@ -2814,10 +2814,14 @@ static inline struct slab_sheaf *alloc_empty_sheaf(struct kmem_cache *s, >>> >>> gfp &= ~OBJCGS_CLEAR_MASK; >>> >>> + if (alloc_flags & SLAB_ALLOC_NOLOCK) >>> + gfp &= ~__GFP_RECLAIM; >> >> So in general we expect gfp and alloc flags to be compatible and warn if >> they are not. This now performs an auto-adjustment, which makes it unusual. > > That's fair. > >> But AFAICS only one caller relies on it - __kfree_rcu_sheaf(). So maybe we >> could just do it there? > > Will do. I don't have strong preference on this. Thanks! >>> return __alloc_empty_sheaf(s, gfp, alloc_flags, s->sheaf_capacity); >>> } >>> >>> -static void free_empty_sheaf(struct kmem_cache *s, struct slab_sheaf *sheaf) >>> +static void __free_empty_sheaf(struct kmem_cache *s, struct slab_sheaf *sheaf, >>> + bool allow_spin) >> >> Why not free_flags instead of allow_spin? Since you already introduced them. > > Indeed I tried that but gave up on doing that as part of series > after realizing free_empty_sheaf() alone has 12 callers :) Yeah but I meant __free_empty_sheaf() only. It's fine to leave the wrapper without the new parameter for the most common case, like you did. > But I think it's worth teaching those functions (including > free_empty_sheaf()) to handle SLAB_ALLOC_* and SLAB_FREE_* flags > rather than propagating allow_spin. It doesn't have to be now :)