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Received: from willy by casper.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1vcqAE-0000000Amk6-1bx5; Mon, 05 Jan 2026 19:22:50 +0000 Date: Mon, 5 Jan 2026 19:22:50 +0000 From: Matthew Wilcox To: Calvin Owens Cc: linux-mm@kvack.org, Andrew Morton , David Hildenbrand , Lorenzo Stoakes Subject: Re: [BUG next-20260105] khugepaged: kernel BUG at ./include/linux/xarray.h:1441 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-Queue-Id: 4AFC0140002 X-Rspamd-Server: rspam04 X-Stat-Signature: 8t6r4dea5frzs3tfdnm4p1smkbgckpqj X-HE-Tag: 1767640973-394169 X-HE-Meta: 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 aqexaF0U N8+dkcaxkf3IQXED8/Mn2RQLgZfKD9GEpnTZ1uEcHUPH+puPlnoKspAMRfv2ea9KEzUyJT0k5tap3lC6eO42D+naRN3KWYVlvQJXExpD44Wt/U+dhlA1R/9kebRwLm6Qn2l1PQHLs2KuT6o66BdrBoCXMzHrMX+RZkmMbqaT5fbPLdte7+vWVKbo9WvpiNrOnRD56fKKQ5MiCt0crTRhiB5yhLSk8yuXJ1lG1r4L4ljNvGvsfuZht1Ox/7A== 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 Mon, Jan 05, 2026 at 10:48:00AM -0800, Calvin Owens wrote: > [ 16.042275][ T58] RIP: 0010:hpage_collapse_scan_file (./include/linux/xarray.h:1441 mm/khugepaged.c:2042 mm/khugepaged.c:2389) Perfect. 2389 is the call to collapse_file(), then 2042 is xas_lock_irq(). And this is exactly the kind of thing we want to be catching; we drop the lock, then reuse the xa_state. In the meantime, the xa_node might have been replaced, and the xa_state now has a pointer to a dead node. It *might* still be safe in this instance; I'll look at this carefully for a bit and decide how best to fix it.