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Fri, 3 Oct 2025 07:49:58 +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 0vEQDSaA32h0ZQAAD6G6ig (envelope-from ); Fri, 03 Oct 2025 07:49:58 +0000 Message-ID: Date: Fri, 3 Oct 2025 09:49:57 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] slab: Fix using this_cpu_ptr() in preemptible context Content-Language: en-US To: ranxiaokai627@163.com, akpm@linux-foundation.org, cl@gentwo.org, rientjes@google.com, roman.gushchin@linux.dev, harry.yoo@oracle.com, ast@kernel.org Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, ran.xiaokai@zte.com.cn References: <20250930083402.782927-1-ranxiaokai627@163.com> 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: <20250930083402.782927-1-ranxiaokai627@163.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Action: no action X-Stat-Signature: 1dqdn689h8isbru5i13odr1pgsupr4cf X-Rspam-User: X-Rspamd-Queue-Id: A7BC4140003 X-Rspamd-Server: rspam10 X-HE-Tag: 1759477800-518415 X-HE-Meta: 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 e/Qe+hbO fgOsJOr7DlAPAfqo= 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 9/30/25 10:34, ranxiaokai627@163.com wrote: > From: Ran Xiaokai > > defer_free() maybe called in preemptible context, this will > trigger the below warning message: > > BUG: using smp_processor_id() in preemptible [00000000] code: swapper/0/1 > caller is defer_free+0x1b/0x60 > Call Trace: > > dump_stack_lvl+0xac/0xc0 > check_preemption_disabled+0xbe/0xe0 > defer_free+0x1b/0x60 > kfree_nolock+0x1eb/0x2b0 > alloc_slab_obj_exts+0x356/0x390 > __alloc_tagging_slab_alloc_hook+0xa0/0x300 > __kmalloc_cache_noprof+0x1c4/0x5c0 > __set_page_owner+0x10d/0x1c0 > post_alloc_hook+0x84/0xf0 > get_page_from_freelist+0x73b/0x1380 > __alloc_frozen_pages_noprof+0x110/0x2c0 > alloc_pages_mpol+0x44/0x140 > alloc_slab_page+0xac/0x150 > allocate_slab+0x78/0x3a0 > ___slab_alloc+0x76b/0xed0 > __slab_alloc.constprop.0+0x5a/0xb0 > __kmalloc_noprof+0x3dc/0x6d0 > __list_lru_init+0x6c/0x210 > alloc_super+0x3b6/0x470 > sget_fc+0x5f/0x3a0 > get_tree_nodev+0x27/0x90 > vfs_get_tree+0x26/0xc0 > vfs_kern_mount.part.0+0xb6/0x140 > kern_mount+0x24/0x40 > init_pipe_fs+0x4f/0x70 > do_one_initcall+0x62/0x2e0 > kernel_init_freeable+0x25b/0x4b0 > kernel_init+0x1a/0x1c0 > ret_from_fork+0x290/0x2e0 > ret_from_fork_asm+0x11/0x20 > > > Replace this_cpu_ptr with raw_cpu_ptr to eliminate > the above warning message. > > Fixes: af92793e52c3 ("slab: Introduce kmalloc_nolock() and kfree_nolock().") > Signed-off-by: Ran Xiaokai Since the slab PR was merged, we should fix this ideally before rc1 so I updated the code myself per the discussion and added to slab/for-next Thanks! ----8<---- >From d6306a3d5577769b179ae4e448fd144e2b0f7717 Mon Sep 17 00:00:00 2001 From: Ran Xiaokai Date: Tue, 30 Sep 2025 08:34:02 +0000 Subject: [PATCH] slab: Fix using this_cpu_ptr() in preemptible context defer_free() maybe called in preemptible context, this will trigger the below warning message: BUG: using smp_processor_id() in preemptible [00000000] code: swapper/0/1 caller is defer_free+0x1b/0x60 Call Trace: dump_stack_lvl+0xac/0xc0 check_preemption_disabled+0xbe/0xe0 defer_free+0x1b/0x60 kfree_nolock+0x1eb/0x2b0 alloc_slab_obj_exts+0x356/0x390 __alloc_tagging_slab_alloc_hook+0xa0/0x300 __kmalloc_cache_noprof+0x1c4/0x5c0 __set_page_owner+0x10d/0x1c0 post_alloc_hook+0x84/0xf0 get_page_from_freelist+0x73b/0x1380 __alloc_frozen_pages_noprof+0x110/0x2c0 alloc_pages_mpol+0x44/0x140 alloc_slab_page+0xac/0x150 allocate_slab+0x78/0x3a0 ___slab_alloc+0x76b/0xed0 __slab_alloc.constprop.0+0x5a/0xb0 __kmalloc_noprof+0x3dc/0x6d0 __list_lru_init+0x6c/0x210 alloc_super+0x3b6/0x470 sget_fc+0x5f/0x3a0 get_tree_nodev+0x27/0x90 vfs_get_tree+0x26/0xc0 vfs_kern_mount.part.0+0xb6/0x140 kern_mount+0x24/0x40 init_pipe_fs+0x4f/0x70 do_one_initcall+0x62/0x2e0 kernel_init_freeable+0x25b/0x4b0 kernel_init+0x1a/0x1c0 ret_from_fork+0x290/0x2e0 ret_from_fork_asm+0x11/0x20 Disable preemption in defer_free() and also defer_deactivate_slab() to make it safe. [vbabka@suse.cz: disable preemption instead of using raw_cpu_ptr() per the discussion ] Fixes: af92793e52c3 ("slab: Introduce kmalloc_nolock() and kfree_nolock().") Signed-off-by: Ran Xiaokai Link: https://lore.kernel.org/r/20250930083402.782927-1-ranxiaokai627@163.com Signed-off-by: Vlastimil Babka --- mm/slub.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/mm/slub.c b/mm/slub.c index 1433f5b988f7..44aa0e3f48ee 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -6432,17 +6432,24 @@ static void free_deferred_objects(struct irq_work *work) static void defer_free(struct kmem_cache *s, void *head) { - struct defer_free *df = this_cpu_ptr(&defer_free_objects); + struct defer_free *df; + guard(preempt)(); + + df = this_cpu_ptr(&defer_free_objects); if (llist_add(head + s->offset, &df->objects)) irq_work_queue(&df->work); } static void defer_deactivate_slab(struct slab *slab, void *flush_freelist) { - struct defer_free *df = this_cpu_ptr(&defer_free_objects); + struct defer_free *df; slab->flush_freelist = flush_freelist; + + guard(preempt)(); + + df = this_cpu_ptr(&defer_free_objects); if (llist_add(&slab->llnode, &df->slabs)) irq_work_queue(&df->work); } -- 2.51.0