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Fri, 23 Jan 2026 06:53:09 +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 0O5fCdUac2k4YgAAD6G6ig (envelope-from ); Fri, 23 Jan 2026 06:53:09 +0000 From: Vlastimil Babka Date: Fri, 23 Jan 2026 07:52:39 +0100 Subject: [PATCH v4 01/22] mm/slab: add rcu_barrier() to kvfree_rcu_barrier_on_cache() MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260123-sheaves-for-all-v4-1-041323d506f7@suse.cz> References: <20260123-sheaves-for-all-v4-0-041323d506f7@suse.cz> In-Reply-To: <20260123-sheaves-for-all-v4-0-041323d506f7@suse.cz> To: Harry Yoo , Petr Tesarik , Christoph Lameter , David Rientjes , Roman Gushchin Cc: Hao Li , Andrew Morton , 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, Vlastimil Babka , kernel test robot , stable@vger.kernel.org X-Mailer: b4 0.14.3 X-Rspamd-Pre-Result: action=no action; module=replies; Message is reply to one we originated X-Rspamd-Action: no action X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 84F42180004 X-Stat-Signature: gsqy44hmst11xwt18pkwaw1x8665whjo X-Rspam-User: X-HE-Tag: 1769151204-890114 X-HE-Meta: U2FsdGVkX1+cVD47+LzDJ6+pXO7Gw9WqvHjeAHnm70gPND8TLJDWSsvSoNo30LoVpjzAia6tHQb0p2Te8Jvx5+ZCt3y+TiOZ/Tg6YSinaG2S/8j1sJ1xNXf+qozW3HDZ29CigSSHHnwnP4/LUXHV/BCs023ajFnRp0qtOk9iqyZqkiHLxVi0ATCnpoTm/05OmdMUDSx1zYduCM2RtIGlFdcQ75fVF1DSJ9iWHA3+1KtL0bPK0B9xEOJRsTCN1ZQ12hJYOpMQKresKDsaz6KCSFpVglW0ZnmpvX40i4FpREiA1OITreJP7c7hF3ng1FUUMubL4kK9Box53fzqLWX17YcS4S/cfIFqxX/GQUISdXy8+mQZGFSDljBSoKZQKyasN1bYlaLfElf23Iumv6bukrSe6Cu/1UOtqgrDM+eP5FEExxYYJnplsAe1i6GZYl+PPuUMuWt68Xz7UbU67UZzD/+eo5IuQNVcR2PzkTlUKo9MJRKjYEL0OSFAOFcs8vEt26VV5V8B30B583pPjVqiK5x6N/1v4AqAX+DSYcDSBJZQO4g3hfb+dZhWp8xkRjTgQNtWyE3aHl1e9xo9NxaWFqSMzbLVOtXMpISKcowCLne8hH8YqDZdZ4iX+81zAYbOSwvsyx1sGiBJOAapYVmXcGS9KBZToaokEIiJcyiFjWCnrQY7CHyF0zzEPfQsuIKVBGsg7H1iBh6V1/MIqF1OqwvgiY4jdMQnTOoH+6Svea7OXiFiCYbY45t/DBMs7LyvrkOWSQSqKEW0tQuEdKnRY5dxOucQzxRri1hrP63jy5Ep9HGT4lgkkysj+DmpkX6I5K01Z1sRUbwBRU6e2u7ABmvtxRNffHnKPsRFg8gefsIodDaiuizKXN6Iwfr26bkmmz1aGlFtnDLQwltN4nVBssZPQ/Rs3ZY0Rq/YXWQr1qddX48j1J5dDDyEEWPjYEqj7RrUeti5EeGVMfrw6d6 bhOwyPvT n0eT8PxOUegPhp9dVLZTdtZDTpoN0R0RbMc3r9GOUPI1lUJXEZcWwCTxI9RF0lKvZXwoRjX5jB9bb2LV/0Vlds+5eUl4jQWqYhF9SoR7DXFE6fV3ztWMoux+pI9fuXVttGF9vNy00fr0p7o2vfPg9JJIdVKdGFzEVSCSJT7lUhDyO7qoxyl+SqAhip4fKdSezFezPzn7fC3cfJ3lxg7cuCExcPwDAG5SHv1scKjIz+XVC1DvTzCbuDKqjJLeH0duFR0ueGtoVaz0ZgRtyQgFENFHqNWrBMPaJu7WfKZ4T/oBma8t8Oc2JbQRNj8Uiasl0jdlygk0CoRC4bF62NfaqA36s1YUajZNYlYPMkGurvOw3CUQHCTyQtGw9i8cIC+6NLisWudlupzI8JpE= 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: After we submit the rcu_free sheaves to call_rcu() we need to make sure the rcu callbacks complete. kvfree_rcu_barrier() does that via flush_all_rcu_sheaves() but kvfree_rcu_barrier_on_cache() doesn't. Fix that. This currently causes no issues because the caches with sheaves we have are never destroyed. The problem flagged by kernel test robot was reported for a patch that enables sheaves for (almost) all caches, and occurred only with CONFIG_KASAN. Harry Yoo found the root cause [1]: It turns out the object freed by sheaf_flush_unused() was in KASAN percpu quarantine list (confirmed by dumping the list) by the time __kmem_cache_shutdown() returns an error. Quarantined objects are supposed to be flushed by kasan_cache_shutdown(), but things go wrong if the rcu callback (rcu_free_sheaf_nobarn()) is processed after kasan_cache_shutdown() finishes. That's why rcu_barrier() in __kmem_cache_shutdown() didn't help, because it's called after kasan_cache_shutdown(). Calling rcu_barrier() in kvfree_rcu_barrier_on_cache() guarantees that it'll be added to the quarantine list before kasan_cache_shutdown() is called. So it's a valid fix! [1] https://lore.kernel.org/all/aWd6f3jERlrB5yeF@hyeyoo/ Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-lkp/202601121442.c530bed3-lkp@intel.com Fixes: 0f35040de593 ("mm/slab: introduce kvfree_rcu_barrier_on_cache() for cache destruction") Cc: stable@vger.kernel.org Reviewed-by: Harry Yoo Tested-by: Harry Yoo Reviewed-by: Suren Baghdasaryan Signed-off-by: Vlastimil Babka --- mm/slab_common.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/mm/slab_common.c b/mm/slab_common.c index eed7ea556cb1..ee994ec7f251 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -2133,8 +2133,11 @@ EXPORT_SYMBOL_GPL(kvfree_rcu_barrier); */ void kvfree_rcu_barrier_on_cache(struct kmem_cache *s) { - if (s->cpu_sheaves) + if (s->cpu_sheaves) { flush_rcu_sheaves_on_cache(s); + rcu_barrier(); + } + /* * TODO: Introduce a version of __kvfree_rcu_barrier() that works * on a specific slab cache. -- 2.52.0