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Fri, 9 Jan 2026 10:11:26 +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 gTGnJk7UYGlzLQAAD6G6ig (envelope-from ); Fri, 09 Jan 2026 10:11:26 +0000 Message-ID: <4fca7893-60bd-41da-844f-971934de19b6@suse.cz> Date: Fri, 9 Jan 2026 11:11:26 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC 14/19] slab: simplify kmalloc_nolock() Content-Language: en-US To: Hao Li Cc: Andrew Morton , Christoph Lameter , David Rientjes , Roman Gushchin , Harry Yoo , Uladzislau Rezki , "Liam R. Howlett" , Suren Baghdasaryan , Sebastian Andrzej Siewior , Alexei Starovoitov , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev, bpf@vger.kernel.org, kasan-dev@googlegroups.com References: <20251023-sheaves-for-all-v1-0-6ffa2c9941c0@suse.cz> <20251023-sheaves-for-all-v1-14-6ffa2c9941c0@suse.cz> <4ukrk3ziayvxrcfxm2izwrwt3qrmr4fcsefl4n7oodc4t2hxgt@ijk63r4f3rkr> 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+fMgqZkBQJnyBr8BQka0IFQAAoJECJPp+fMgqZkqmMQ AIbGN95ptUMUvo6aAdhxaOCHXp1DfIBuIOK/zpx8ylY4pOwu3GRe4dQ8u4XS9gaZ96Gj4bC+ jwWcSmn+TjtKW3rH1dRKopvC07tSJIGGVyw7ieV/5cbFffA8NL0ILowzVg8w1ipnz1VTkWDr 2zcfslxJsJ6vhXw5/npcY0ldeC1E8f6UUoa4eyoskd70vO0wOAoGd02ZkJoox3F5ODM0kjHu Y97VLOa3GG66lh+ZEelVZEujHfKceCw9G3PMvEzyLFbXvSOigZQMdKzQ8D/OChwqig8wFBmV QCPS4yDdmZP3oeDHRjJ9jvMUKoYODiNKsl2F+xXwyRM2qoKRqFlhCn4usVd1+wmv9iLV8nPs 2Db1ZIa49fJet3Sk3PN4bV1rAPuWvtbuTBN39Q/6MgkLTYHb84HyFKw14Rqe5YorrBLbF3rl M51Dpf6Egu1yTJDHCTEwePWug4XI11FT8lK0LNnHNpbhTCYRjX73iWOnFraJNcURld1jL1nV r/LRD+/e2gNtSTPK0Qkon6HcOBZnxRoqtazTU6YQRmGlT0v+rukj/cn5sToYibWLn+RoV1CE Qj6tApOiHBkpEsCzHGu+iDQ1WT0Idtdynst738f/uCeCMkdRu4WMZjteQaqvARFwCy3P/jpK uvzMtves5HvZw33ZwOtMCgbpce00DaET4y/UzsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZ8gcVAUJFhTonwAKCRAiT6fnzIKmZLY8D/9uo3Ut9yi2YCuASWxr7QQZ lJCViArjymbxYB5NdOeC50/0gnhK4pgdHlE2MdwF6o34x7TPFGpjNFvycZqccSQPJ/gibwNA zx3q9vJT4Vw+YbiyS53iSBLXMweeVV1Jd9IjAoL+EqB0cbxoFXvnjkvP1foiiF5r73jCd4PR rD+GoX5BZ7AZmFYmuJYBm28STM2NA6LhT0X+2su16f/HtummENKcMwom0hNu3MBNPUOrujtW khQrWcJNAAsy4yMoJ2Lw51T/5X5Hc7jQ9da9fyqu+phqlVtn70qpPvgWy4HRhr25fCAEXZDp xG4RNmTm+pqorHOqhBkI7wA7P/nyPo7ZEc3L+ZkQ37u0nlOyrjbNUniPGxPxv1imVq8IyycG AN5FaFxtiELK22gvudghLJaDiRBhn8/AhXc642/Z/yIpizE2xG4KU4AXzb6C+o7LX/WmmsWP Ly6jamSg6tvrdo4/e87lUedEqCtrp2o1xpn5zongf6cQkaLZKQcBQnPmgHO5OG8+50u88D9I rywqgzTUhHFKKF6/9L/lYtrNcHU8Z6Y4Ju/MLUiNYkmtrGIMnkjKCiRqlRrZE/v5YFHbayRD dJKXobXTtCBYpLJM4ZYRpGZXne/FAtWNe4KbNJJqxMvrTOrnIatPj8NhBVI0RSJRsbilh6TE m6M14QORSWTLRg== In-Reply-To: <4ukrk3ziayvxrcfxm2izwrwt3qrmr4fcsefl4n7oodc4t2hxgt@ijk63r4f3rkr> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: z17a97botr9f6btj59iufbhhw5uciwz6 X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 4DCCB180007 X-Rspam-User: X-HE-Tag: 1767953488-854456 X-HE-Meta: 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 7ks3EUk1 0SiAY7rZk/sCVpMXauizUy2NnxnZkMII28QRFYlrh/F9+nCOIF5ujusQps7ixC4nfZGrDnwDIO40CLG2WTjeWFd+ZZ1Aa5SQS6wzlVx+1O0wif2+aAzinenELOXnmzWFDc/3AvvwK4sE+NhSEO/B2byWtN4WXWo6c6Mj2qmprc3jmqkDXXtJhuZylxPEJ0D6Q5nmBWmCqi5gZyNPeytazqufERxwT0YnU93eGSSu4z/Vulp66Lo2hSVikpmyqPstrli7/M9Y34JkNgl3kKsiaEuzHxhDdI9ettJ9fOVwwCEaZ5mAN65Qk2xdLzGmvJ44XlAR+Reyfsms+maI= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, 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 12/16/25 03:35, Hao Li wrote: > On Thu, Oct 23, 2025 at 03:52:36PM +0200, Vlastimil Babka wrote: >> @@ -5214,27 +5144,13 @@ void *kmalloc_nolock_noprof(size_t size, gfp_t gfp_flags, int node) >> if (ret) >> goto success; >> >> - ret = ERR_PTR(-EBUSY); >> - >> /* >> * Do not call slab_alloc_node(), since trylock mode isn't >> * compatible with slab_pre_alloc_hook/should_failslab and >> * kfence_alloc. Hence call __slab_alloc_node() (at most twice) >> * and slab_post_alloc_hook() directly. >> - * >> - * In !PREEMPT_RT ___slab_alloc() manipulates (freelist,tid) pair >> - * in irq saved region. It assumes that the same cpu will not >> - * __update_cpu_freelist_fast() into the same (freelist,tid) pair. >> - * Therefore use in_nmi() to check whether particular bucket is in >> - * irq protected section. >> - * >> - * If in_nmi() && local_lock_is_locked(s->cpu_slab) then it means that >> - * this cpu was interrupted somewhere inside ___slab_alloc() after >> - * it did local_lock_irqsave(&s->cpu_slab->lock, flags). >> - * In this case fast path with __update_cpu_freelist_fast() is not safe. >> */ >> - if (!in_nmi() || !local_lock_is_locked(&s->cpu_slab->lock)) >> - ret = __slab_alloc_node(s, alloc_gfp, node, _RET_IP_, size); >> + ret = __slab_alloc_node(s, alloc_gfp, node, _RET_IP_, size); >> >> if (PTR_ERR(ret) == -EBUSY) { > > After Patch 10 is applied, the logic that returns `EBUSY` has been > removed along with the `s->cpu_slab` logic. As a result, it appears that > `__slab_alloc_node` will no longer return `EBUSY`. True, I missed that, thanks. Since we can still get failures due to the cpu_sheaves local lock held, I think we could just do the single retry with a larger bucket if ret is NULL. Whlle it may be NULL for other reasons (being genuinely out of memory and the limited context not allowing reclaim etc), it wouldn't hurt, and it's better than to introduce returning EBUSY into various paths. >> if (can_retry) { >> @@ -7250,10 +7166,6 @@ void __kmem_cache_release(struct kmem_cache *s) >> { >> cache_random_seq_destroy(s); >> pcs_destroy(s); >> -#ifdef CONFIG_PREEMPT_RT >> - if (s->cpu_slab) >> - lockdep_unregister_key(&s->lock_key); >> -#endif >> free_percpu(s->cpu_slab); >> free_kmem_cache_nodes(s); >> } >> >> -- >> 2.51.1 >>