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[44.242.192.44]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3a0b4f5b1aasm936305a91.1.2026.09.24.22.32.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 24 Sep 2026 22:32:18 -0700 (PDT) From: Ayush Ranjan To: Jan Kara Cc: Ayush Ranjan , Hugh Dickins , Matthew Wilcox , Andrew Morton , Pedro Falcato , Baolin Wang , David Hildenbrand , Gregory Price , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [BUG] shmem: FALLOC_FL_PUNCH_HOLE vs fault-around race corrupts page cache / rss counters Date: Fri, 25 Sep 2026 05:32:10 +0000 Message-ID: <20260925053211.2036445-1-ayushr@modal.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: References: <20260924061708.1645968-1-ayushr@modal.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 77CFC40005 X-Stat-Signature: 43ok683dn9kj3s8e1kzyf76no8stst38 X-HE-Tag: 1790314340-907958 X-HE-Meta: U2FsdGVkX1+BEmbChe0e6sueaelvkRhnpX6JI8vkDwtqh6dqqvO9n8koL6iFv32vgDbwwLx1jlOPiYtvnBeY/H7n1E2HShAZB/w1hPaEUeO3Ud/GhbPaC/rWe4t5dhJwVqi1FQgbL/a4gh+x623W8/FfhSI56DJFjwI/Fh9rGViWoajkvAFXvHLkuWclYxmRfMEufkZB/umJA3a63JlYOJ5j+JoN5NXv4Qz9i1OZ5HGjGU2ryDeS6Buw59BemljicCSJERL1xC/YIl23X2jSvLqalIhj5b9+8AoRWSgbvplo4qG24C28CUU0nIRj5B68tS4MAwO1L53YGD3tRI0/GadtxgCPsGmY8AlLOcuBzuOj0QJ/jDLL8+Arz/CpDkg9YqAOvEvfD4V6ddwmBb75t3bk3uOb1hkipAf8mget9qWGJ2aS9jNDPa64QnAZu5ROthiO8YufQ+DTD2Yyv4iCKbNHQe3GyZPNzui9qJ772XZFPpB4IaWJo7zZe7af2u9X1F7TnKF5bCoPwAn454XCKRsl9go3xFhZomkPdInSgVCg06P5czoBJLemqNK+bOujg1Zz8zgeuVwXm6eqY8NgIfTM3DcuoX/5wghprWhclUbLD/186tSqWHN6JG5fjIKLtnsfPtxeThim4BXtgBbpkhjzqmbpVh6mKhs7BNAvXRkhlt1aDm2pkFHT7p6PziBY3G7DvqpZEDFieHWAHPGcpISU2N5Id5rWRQ15HitAA3y2xTySuf/q/v7pJQudXH0t1/Z+K3RQBcwSdZDiCdt7cNHuQKmZ3zLP4mtUJMu3KC0NG3iGNtAlYcm1KboiVXvo9xBhThZVRcpGTdlNdw9rrGi6S3e5MOoRrwxkDbhTcaG2t2ZgjZAQWdCwUy2MTMKKfPC+39agtPC/Ck7/S1Iwo2lTFB0kybegB9nVMqwum6uPEqdVEPbSUGNPtqH7e+qPm9cKZSE2Mgc/6Mx31VT u11O1HDd AzmptalB0elLlmh2VjOa1RKuaH82Z+cUXlSUO/Ssgf9lyl6naUuMy86VyRNoSLj7a7pYGpGgpYe0/fTlkIf7o6fpNx2TLJWneYZrigZkoz5gFDPikD6+xybydJIILmcUKD+49WXTLvhLb1nWx6GT7SnZ4daa91CMWF4GubMGaYIvnnKD8pauSLku+DkWz/mg9hsFFr+RIplgFLRmz6zLbHA+29S6Qp/csROD9jQKO1JVNyoRPlzTxMYJR1RcmClq81YU92Ld5Cfws1bCCL4yiM/11O7Fm/aPJS11OBEfhypsiOb1PmY2Qqm8JkQsi7Bb69SOnjqDNobjCBhE9ee4Hy1zpkuyz+bDlF0dDWEtVQzA+SOsIlBBByiolsWzmw4xWWyarvluPpfwetxC1mceQt6vMTg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Sep 24, 2026 at 09:15 +0000, Jan Kara wrote: > Can this be perhaps somehow related to the fixes in partial large folio > truncation Zhang Yi is working on, possibly even the tmpfs bug in handling > of folio split I've found [1]? It seems large folios are used here so that > matches, I just don't immediately see how those bugs would lead to the > errors reported here... That would fit what I see, for what it's worth: - the rss-counter imbalance from the reproducer is always exactly one PMD-order folio (+/-512), which looks more like large-folio split/accounting going wrong than lost or extra PTEs; - the reproducer's punching thread deliberately mixes unaligned sub-PMD ranges, so partial truncation of large folios is exercised constantly, and the production "still mapped when deleted" splat is reported from truncate_inode_partial_folio() (full stack in my reply to Pedro). Thanks, Ayush