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Received: from viro by zeniv.linux.org.uk with local (Exim 4.99 #2 (Red Hat Linux)) id 1vTvIP-0000000AkHR-47w8; Fri, 12 Dec 2025 05:02:26 +0000 Date: Fri, 12 Dec 2025 05:02:25 +0000 From: Al Viro To: Hugh Dickins Cc: Christian Brauner , Andrew Morton , Baolin Wang , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: 6.19 tmpfs __d_lookup() lockup Message-ID: <20251212050225.GD1712166@ZenIV> References: <47e9d03c-7a50-2c7d-247d-36f95a5329ed@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <47e9d03c-7a50-2c7d-247d-36f95a5329ed@google.com> X-Stat-Signature: 6yzmgyoe4uqykqaj5mybuqdd4ws7nqes X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: B415EA0010 X-HE-Tag: 1765515719-157322 X-HE-Meta: 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 zhJ6hcGN bWzYZ8uB26gPKofM6O6jbbUkYQy/50gK6KzFTeuQZ/Dx18RHtHO0o3R2QqbaqsDfsHJpGjhPcly0vw6jaLiQMolQoQ8PPd1HRpmeYND+1ulT2HuWRhj3mG45FXSKHFHNeXKz/ponEqcMKcsXsZSDZ5dznHaqJrJga8uuLHkgGanLpnwOT01LaGwEHWLc1KViCdLPbDG3pHk8pRxesMjGZeq9rS3xChi9n8jvkG9f1GS2gP1gEuOkC6Mg2Lo9rndUTD2npcebAmQaPryXJUvD8GlWZeSYm8EAy5BIcQrPZdNpDXMbYL2zjC3reFbk2bIOTBezsgWBJUInMJwcQaPTt4LgfewIAESw/w5Ox9eqXmAIlqtWTb1fqDgBD0zSefVvNMyLg/lAoGUIQ+Uiy7G8ZDBp2cRsaCTaoanXOuKwTysVFqmePVzNVQ0VcSEU1C05hZkOclOJHYQ3jwhHEtF3jO+SIHc9atFqpnhuxP3Vpr6+s3eE= 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 Thu, Dec 11, 2025 at 07:56:38PM -0800, Hugh Dickins wrote: > Of course, 2313598222f9 ("convert ramfs and tmpfs") (of Feb 26 2024!) > comes out as the first failing commit, no surprise there. > > I did try inserting a BUG_ON(node == node->next) on line 2438 of > fs/dcache.c, just after __d_lookup's hlist_bl_for_each_entry_rcu(), > and that BUG was immediately hit (but, for all I know, perhaps that's > an unreliable asserition, perhaps it's acceptable for a race to result > in a momentary node == node->next there). Hmm... Could you check if we are somehow hitting d_in_lookup(dentry) in d_make_persistent()?