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 ADF753A4F47; Mon, 22 Jun 2026 11:27:47 +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=1782127669; cv=none; b=eVZH/Zgg4diWX7A/vL3ZM6uOVUNs8pT0j/SkTQFOGa4nttJDYAzZ1tNHNj9BbowU657N/sBrd02KpbdAMq5ICKU1evE98i+LuoBSxd/vJjNFw0Uz6vDHy+31UMYdiFcaOkPb/LZe/PAd5h7L01K8P8lvZ2ZREaTEPDNsWLbGh+s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782127669; c=relaxed/simple; bh=N/vuDHI9SQW1janB0j5sO1lsg3p3zPSFITHHbgn1I9o=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=N6BSQiUlze+NFvrkVh5/fninGhgV2NrV1roGLM0qGbypx0hb7Z0Kf/1BM9MBGcyUjr8tbjJqaA7Tg4JzDhDs5ZyVqzzLxKsB7548qWFBecXGhk6lOxjaf7mAlCtlp1XBCsQfx+aPtIXP0JU5aLOwIuhHjj9lxRfMN1yAk95Q6zI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=NP5vIVfj; 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="NP5vIVfj" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8AED81F000E9; Mon, 22 Jun 2026 11:27:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782127667; bh=CxKnwWbJ6o3Gp2gCYHflIyVCw0BGlYpweEWWlR7Zxlc=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=NP5vIVfjsp4feyIcuAfoiRvYPwPZKLTXzyb0N0wUNoKxJZDnW14mB+Ksso1zMBEZX fUxTpjrKClw00GwNOT/ge4xL2rriBHbh5PxOP732GJlaoArFBmxyEOXdYsklIEobB9 /pFQVIcOni9/exs8OPh0iGTCF0YrB1elReGRM0Pk+0VV64ksMWO5Yff5O4AFlcbETU 7oQHcuU8AyNBq9zKQ3Q/5sFiPWawUkfJJPp52WQ+UesWgVbFX7LlIhxh77+4lU8xhN 0Mxv8uME2L+nRo7wVhECL6694CE+9AKg1Xt97qlcIjmOAoH39Xw4JyyfVaAkL3HiaO P5VjuChOEJC/w== Message-ID: <8f98a3a6-f97b-4673-964f-fb09c8879e2e@kernel.org> Date: Mon, 22 Jun 2026 13:27:34 +0200 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 0/7] Prepare mutable list iterators to cache cursor state To: Alexei Starovoitov , Kaitao Cheng Cc: Andrew Morton , Jens Axboe , Tejun Heo , Alexander Viro , Christian Brauner , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Johannes Weiner , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , Thomas Gleixner , Juri Lelli , Vincent Guittot , Paul Moore , Andy Shevchenko , "Paul E. McKenney" , Shakeel Butt , =?UTF-8?Q?Christian_K=C3=B6nig?= , David Howells , Simona Vetter , Randy Dunlap , Luca Ceresoli , Philipp Stanner , linux-block@vger.kernel.org, LKML , "open list:CONTROL GROUP (CGROUP)" , linux-ntfs-dev@lists.sourceforge.net, Linux-Fsdevel , io-uring , audit@vger.kernel.org, bpf , Network Development , dri-devel@lists.freedesktop.org, "linux-perf-use." , linux-trace-kernel , kexec@lists.infradead.org, live-patching@vger.kernel.org, linux-modules@vger.kernel.org, Linux Crypto Mailing List , Linux Power Management , rcu@vger.kernel.org, sched-ext@lists.linux.dev, linux-mm , virtualization@lists.linux.dev, damon@lists.linux.dev, clang-built-linux , chengkaitao References: <20260622040533.29824-1-kaitao.cheng@linux.dev> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 6/22/26 07:28, Alexei Starovoitov wrote: > On Sun, Jun 21, 2026 at 9:06 PM Kaitao Cheng wrote: >> >> From: chengkaitao >> >> The list_for_each*_safe() helpers are used when the loop body may remove >> the current entry. Their current interface, however, forces every caller >> to define a temporary cursor outside the macro and pass it in, even when >> the caller never uses that cursor directly. For most call sites this >> extra cursor is just boilerplate required by the macro implementation. >> >> This is awkward because the saved next pointer is an internal detail of >> the iteration. Callers that only remove or move the current entry do not >> need to spell it out. >> >> The _safe() suffix has also caused confusion. Christian Koenig pointed >> out that the name is easy to read as a thread-safe variant, especially >> for beginners, even though it only means that the iterator keeps enough >> state to tolerate removal of the current entry. He suggested _mutable() >> as a clearer description of what the loop permits. >> >> Add *_mutable() iterator variants for list, hlist and llist. The new >> helpers are variadic and support both forms. In the common case, the >> caller omits the temporary cursor and the macro creates a unique internal >> cursor with typeof(pos) and __UNIQUE_ID(). If a loop really needs an >> explicit temporary cursor, the caller can still pass it and the helper >> keeps the existing *_safe() behaviour. >> >> For example, a call site may use the shorter form: >> >> list_for_each_entry_mutable(pos, head, member) >> >> or keep the explicit temporary cursor form: >> >> list_for_each_entry_mutable(pos, tmp, head, member) >> >> The existing *_safe() helpers remain available for compatibility. This >> series only converts users in mm, block, kernel, init and io_uring. If >> this approach looks acceptable, the remaining users can be converted in >> follow-up series. >> >> Changes in v3 (Christian König, Andy Shevchenko): >> - Convert safe list walks to mutable iterators >> >> Changes in v2 (Muchun Song, Andy Shevchenko): >> - Drop the list_for_each_entry_mutable*() helpers from v1 and make the >> cursor change directly in the existing list_for_each_entry*() helpers. >> - Open-code special list walks that rely on updating the loop cursor in >> the body, preserving their existing traversal semantics. >> >> Link to v2: >> https://lore.kernel.org/all/20260609061347.93688-1-kaitao.cheng@linux.dev/ >> >> Link to v1: >> https://lore.kernel.org/all/20260529082149.76764-1-kaitao.cheng@linux.dev/ >> >> Kaitao Cheng (7): >> list: Add mutable iterator variants >> llist: Add mutable iterator variants >> mm: Use mutable list iterators >> block: Use mutable list iterators >> kernel: Use mutable list iterators >> initramfs: Use mutable list iterator >> io_uring: Use mutable list iterators >> >> block/bfq-iosched.c | 17 +- >> block/blk-cgroup.c | 12 +- >> block/blk-flush.c | 4 +- >> block/blk-iocost.c | 18 +- >> block/blk-mq.c | 8 +- >> block/blk-throttle.c | 4 +- >> block/kyber-iosched.c | 4 +- >> block/partitions/ldm.c | 8 +- >> block/sed-opal.c | 4 +- >> include/linux/list.h | 269 ++++++++++++++++++++++++---- >> include/linux/llist.h | 81 +++++++-- >> init/initramfs.c | 5 +- >> io_uring/cancel.c | 6 +- >> io_uring/poll.c | 3 +- >> io_uring/rw.c | 4 +- >> io_uring/timeout.c | 8 +- >> io_uring/uring_cmd.c | 3 +- >> kernel/audit_tree.c | 4 +- >> kernel/audit_watch.c | 16 +- >> kernel/auditfilter.c | 4 +- >> kernel/auditsc.c | 4 +- >> kernel/bpf/arena.c | 10 +- >> kernel/bpf/arraymap.c | 8 +- >> kernel/bpf/bpf_local_storage.c | 3 +- >> kernel/bpf/bpf_lru_list.c | 25 ++- >> kernel/bpf/btf.c | 18 +- >> kernel/bpf/cgroup.c | 7 +- >> kernel/bpf/cpumap.c | 4 +- >> kernel/bpf/devmap.c | 10 +- >> kernel/bpf/helpers.c | 8 +- >> kernel/bpf/local_storage.c | 4 +- >> kernel/bpf/memalloc.c | 16 +- >> kernel/bpf/offload.c | 8 +- >> kernel/bpf/states.c | 4 +- >> kernel/bpf/stream.c | 4 +- >> kernel/bpf/verifier.c | 6 +- >> kernel/cgroup/cgroup-v1.c | 4 +- >> kernel/cgroup/cgroup.c | 54 +++--- >> kernel/cgroup/dmem.c | 12 +- >> kernel/cgroup/rdma.c | 8 +- >> kernel/events/core.c | 44 +++-- >> kernel/events/uprobes.c | 12 +- >> kernel/exit.c | 8 +- >> kernel/fail_function.c | 4 +- >> kernel/gcov/clang.c | 4 +- >> kernel/irq_work.c | 4 +- >> kernel/kexec_core.c | 4 +- >> kernel/kprobes.c | 16 +- >> kernel/livepatch/core.c | 4 +- >> kernel/livepatch/core.h | 4 +- >> kernel/liveupdate/kho_block.c | 4 +- >> kernel/liveupdate/luo_flb.c | 4 +- >> kernel/locking/rwsem.c | 2 +- >> kernel/locking/test-ww_mutex.c | 2 +- >> kernel/module/main.c | 11 +- >> kernel/padata.c | 4 +- >> kernel/power/snapshot.c | 8 +- >> kernel/power/wakelock.c | 4 +- >> kernel/printk/printk.c | 11 +- >> kernel/ptrace.c | 4 +- >> kernel/rcu/rcutorture.c | 3 +- >> kernel/rcu/tasks.h | 9 +- >> kernel/rcu/tree.c | 6 +- >> kernel/resource.c | 4 +- >> kernel/sched/core.c | 4 +- >> kernel/sched/ext.c | 22 +-- >> kernel/sched/fair.c | 28 +-- >> kernel/sched/topology.c | 4 +- >> kernel/sched/wait.c | 4 +- >> kernel/seccomp.c | 4 +- >> kernel/signal.c | 11 +- >> kernel/smp.c | 4 +- >> kernel/taskstats.c | 8 +- >> kernel/time/clockevents.c | 6 +- >> kernel/time/clocksource.c | 4 +- >> kernel/time/posix-cpu-timers.c | 4 +- >> kernel/time/posix-timers.c | 3 +- >> kernel/torture.c | 3 +- >> kernel/trace/bpf_trace.c | 4 +- >> kernel/trace/ftrace.c | 49 +++-- >> kernel/trace/ring_buffer.c | 25 ++- >> kernel/trace/trace.c | 12 +- >> kernel/trace/trace_dynevent.c | 6 +- >> kernel/trace/trace_dynevent.h | 5 +- >> kernel/trace/trace_events.c | 35 ++-- >> kernel/trace/trace_events_filter.c | 4 +- >> kernel/trace/trace_events_hist.c | 8 +- >> kernel/trace/trace_events_trigger.c | 17 +- >> kernel/trace/trace_events_user.c | 16 +- >> kernel/trace/trace_stat.c | 4 +- >> kernel/user-return-notifier.c | 3 +- >> kernel/workqueue.c | 16 +- >> mm/backing-dev.c | 8 +- >> mm/balloon.c | 8 +- >> mm/cma.c | 4 +- >> mm/compaction.c | 4 +- >> mm/damon/core.c | 4 +- >> mm/damon/sysfs-schemes.c | 4 +- >> mm/dmapool.c | 4 +- >> mm/huge_memory.c | 8 +- >> mm/hugetlb.c | 56 +++--- >> mm/hugetlb_vmemmap.c | 16 +- >> mm/khugepaged.c | 14 +- >> mm/kmemleak.c | 7 +- >> mm/ksm.c | 25 +-- >> mm/list_lru.c | 4 +- >> mm/memcontrol-v1.c | 8 +- >> mm/memory-failure.c | 12 +- >> mm/memory-tiers.c | 4 +- >> mm/migrate.c | 23 ++- >> mm/mmu_notifier.c | 9 +- >> mm/page_alloc.c | 8 +- >> mm/page_reporting.c | 2 +- >> mm/percpu.c | 11 +- >> mm/pgtable-generic.c | 4 +- >> mm/rmap.c | 10 +- >> mm/shmem.c | 9 +- >> mm/slab_common.c | 14 +- >> mm/slub.c | 33 ++-- >> mm/swapfile.c | 4 +- >> mm/userfaultfd.c | 12 +- >> mm/vmalloc.c | 24 +-- >> mm/vmscan.c | 7 +- >> mm/zsmalloc.c | 4 +- >> 124 files changed, 875 insertions(+), 681 deletions(-) > > Not sure what you were thinking, but this diff stat > is not landable. Agreed. If we decide we want this, I guess we should target per-subsystem conversions. If this goes through the MM tree, I would even appreciate doing this on a per-MM component granularity. (unless we have some magic "Linus converts all of them" script, which I doubt we will have) Is there a way forward to replace list_for_each_*_safe entirely, possibly just reusing the old name but simply the parameter? -- Cheers, David