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Fri, 28 Aug 2026 16:53:51 +0000 X-Mizu-Trace-ID: 4322b439f1cc1ba4 X-Migadu-Flow: FLOW_OUT Date: Fri, 28 Aug 2026 09:53:50 -0700 From: Shakeel Butt To: Farhad Alemi Cc: Johannes Weiner , Michal Hocko , Roman Gushchin , Andrew Morton , falemi@asu.edu, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [BUG] refill_stock -- VM_WARN_ON_ONCE(mem_cgroup_is_root()) from a write to the cgroup-v2 root's memory.reclaim Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: A2A3210000C X-Stat-Signature: c18ht5yfoujqxcuu6u7eg1rnbdjz61hn X-HE-Tag: 1787936050-912153 X-HE-Meta: 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 7fnotkAw zG37Rny8R4JTWt8jci3DUrFR9/ctJ/i161HW6tD09o7jlBBlccpkEjrbEoUGwH5KX2SVXm4lWWt+37x0Skuq+N6bngdG7m4RxD5H4/BxOH66NKfH3QtGKyKo6RGpWHuVQ/vX6kNyjQ2PLJnugup9Mce0+/ojQkBE64+lSUvXUlA0YKySXttfg4M44FM1xq6jZfTHhKeQMMnVMk+SX1AcTum4gujzo9Zm8eSnz7PMrHUNIWDR9kWNSKMgi7wUVGBwDHk4jLUPkHQSPoJxXID6S/u2LAIog9h7e5+or1i4sqhaqvl41GyIh+woj/mK3NzdXqQgYBBx+0SXPyyj3rcwfGhYdiFGIts/084twmeRhXFGrNIlAzdCeoVv8xw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Aug 27, 2026 at 10:28:57PM -0700, Farhad Alemi wrote: > Hello, > > As part of the kernel research at ASU's SEFCOM > lab, we hit the crash below. Crash reports can be found here: > > https://github.com/farhad-alemi/public_bug_reports/tree/main/145-memcg-vm_warn-refill_stock-root-cgroup/ > > mem_cgroup_is_root(memcg) > WARNING: mm/memcontrol.c:2198 at refill_stock+0x644/0x940, CPU#1: repro/9490 > Call Trace: > refill_stock+0x644/0x940 > try_charge_memcg+0x12d6/0x1570 > __obj_cgroup_charge+0x35/0xf0 > obj_cgroup_charge+0x1de/0x210 > obj_cgroup_charge_zswap+0x83/0x270 > zswap_store+0x1620/0x2000 > swap_writeout+0x94c/0x14c0 > shrink_folio_list+0x3388/0x52b0 > evict_folios+0x374d/0x48c0 > try_to_shrink_lruvec+0xe72/0x1350 > shrink_node+0x3320/0x3b90 > do_try_to_free_pages+0x6a2/0x1990 > try_to_free_mem_cgroup_pages+0x30d/0x830 > user_proactive_reclaim+0x504/0x840 > memory_reclaim+0x1f/0x30 > cgroup_file_write+0x331/0x8f0 > kernfs_fop_write_iter+0x3af/0x540 > > Our reproducer.c is available upon request. > > Happy to test a patch if that would help. Thanks for the report. Please test the following patch. I will send formal patch after your testing. diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 4a18ee4509ab..1709ac96bbde 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -3157,7 +3157,7 @@ static int obj_cgroup_charge_pages(struct obj_cgroup *objcg, gfp_t gfp, memcg = get_mem_cgroup_from_objcg(objcg); - ret = try_charge_memcg(memcg, gfp, nr_pages); + ret = try_charge(memcg, gfp, nr_pages); if (ret) goto out;