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b=IWYBmbailcCty1MPeh6h9jE9H5U5hJVIncLh+4HoUsE7ZZOyQJ473Kf1OS54kV7V1 XM8cfvQOCkb0WSdaGA0u6f/inBwvuHPD/BbNkfRq5J7j5jBcMtbbZdKljHrbUs17gw aO77a7biIJ9LcJyYYit35g5pidTPBUAHq5bsHWRs= Date: Fri, 24 Apr 2026 03:42:42 -0700 From: Andrew Morton To: Arjan van de Ven Cc: linux-mm@kvack.org, syzbot+9722a25de70a85ff48a1@syzkaller.appspotmail.com, baolin.wang@linux.alibaba.com, hughd@google.com, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Subject: Re: [syzbot] [mm?] BUG: sleeping function called from invalid context in shmem_undo_range Message-Id: <20260424034242.b3e888872e8af6bedb882c1c@linux-foundation.org> In-Reply-To: <20260424023524.322251-1-arjan@linux.intel.com> References: <69eab803.a00a0220.17a17.004b.GAE@google.com> <20260424023524.322251-1-arjan@linux.intel.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: A0E961C000D X-Rspamd-Server: rspam12 X-Stat-Signature: doyxxpfjwo41nu18g8qxxt134ja6m5p8 X-Rspam-User: X-HE-Tag: 1777027364-698696 X-HE-Meta: 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 NFAM6Q2D 1cAq5dDMx6eL5YqCCffQl3W5FtgUpb+GwiSLZGczVwC9WcmAEINgqy6MLCwge0Reru1FkPZncd4QsOwYpzAMGfa0ZP0qJ5RPZ29glZ155tOLzvMOfMpzp5sbtws5vbwiKdEa2a1fgU7pwr1SABDrYJv8NsbH1e0e6AfV9K2nPgPk3FtAOknB7cV7VN5S7xzzES8M1nIt0t7tR7xJZS6RMf/Srp4DC8QN3kpfFRqUaNgGx8pUseDk4SdPQrnBY/4+cLhzfiY65v+8NhsdpVLS6JANChoyZwUXU0BJDK5A9S+i4J0apFnuEgpHbukCfLxfX/ZYjxN5HQjIkaUWr2is1dGX1qYzyGZ3joBmbtU8OuQNm+Dx6LkHyOr+aJKomquWHQcitPThld3C7dQGcgMb7YiEth6alziKzJ1TB1rAx26mHg0hfnhSPz1S/RLrEQoPxjoQtVQypzz8ZfHo= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, 23 Apr 2026 19:34:54 -0700 Arjan van de Ven wrote: > This email is created by automation to help kernel developers > deal with a large volume of AI generated bug reports by decoding > oopses into more actionable information. Thanks ;) > > ... > > Potential Solution > > Find the rcu_read_lock() call that is missing its matching > rcu_read_unlock() in the vfs_unlink() / fsnotify_unlink() / > d_delete_notify() code path. Adding a WARN_ON(rcu_read_lock_held()) > to iput() (alongside the existing might_sleep() check) should produce > a backtrace pointing at the exact acquisition site on the next > reproduction. yup, if we had a reproducer! What's missing from the lockdep report is the one thing we want to know - where did that rcu_read_lock() occur? All we have is > #1: ffffffff8e7e5260 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire.constprop.0+0x7/0x30 include/linux/rcupdate.h:300 which isn't very useful! lockdep records the stack trace for the acquisition site, so why didn't we get to see that?