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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id 956f58d0204a3-64477dab9fbsm2184061d50.14.2025.12.11.23.17.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 11 Dec 2025 23:17:59 -0800 (PST) Date: Thu, 11 Dec 2025 23:17:46 -0800 (PST) From: Hugh Dickins To: Al Viro cc: Hugh Dickins , 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 In-Reply-To: <20251212063026.GF1712166@ZenIV> Message-ID: <2a102c6d-82d9-2751-cd31-c836b5c739b7@google.com> References: <47e9d03c-7a50-2c7d-247d-36f95a5329ed@google.com> <20251212050225.GD1712166@ZenIV> <20251212053452.GE1712166@ZenIV> <8ab63110-38b2-2188-91c5-909addfc9b23@google.com> <20251212063026.GF1712166@ZenIV> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII On Fri, 12 Dec 2025, Al Viro wrote: > On Thu, Dec 11, 2025 at 09:57:15PM -0800, Hugh Dickins wrote: > > > No, sad to say, CONFIG_UNICODE is not set. > > > > (I see why you're asking, I did notice from the diff that the > > case-folding stuff in shmem.c used to do something different but > > now the same in several places; but the case-folding people will > > have to look out for themselves, it's beyond me.) > > > > (And yes, I was being stupid in my previous response: once I looked > > at how simple d_in_lookup() is, I understood your "hitting"; but at > > least I gave the right answer, no, that warning does not show up.) > > A few more things to check: > > 1) do we, by any chance, ever see dentry_free() called with > dentry->d_flags & DCACHE_PERSISTENT? No. > > 2) does d_make_persistent() ever call __d_rehash() when called with > dentry->d_sb->s_magic == TMPFS_MAGIC? Yes, both if shmem_whiteout() does its d_rehash() and if it does not. > > 3) is shmem_whiteout() ever called? If that's the case, could you try > to remove that d_rehash() call in it and see what happens? Because > that's another place where shmem is playing odd games... Yes, shmem_whiteout() does get called. And when I remove that d_rehash() call from it, 269 476 650 and 750 complete without locking up. And when I remove the WARN_ON()s inserted for 2) and 3), then they pass. You are very much on the right lines! Hugh