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b=r5rGUtxbTEFRVIwKmrHc2xHpl8euv4Jw61qaIMJHTpRKz2a4Wpu0xrGEmM+eetht/ 4kyUSIxUQSya+dfCBPaIyUSuOepCAXBVpCLeUw9fXTaK0jHnNxz6JsxoBI0MeNnHe/ vId4RJ2fHC56O9ppqki5yeCg8P2YagaI8NbnorlgkUhxqq4FrrxrB8qQpQ47T0KUNW eYsitdf330m4rKkulB74dq5rn6lk3DOk5FWv5qS9Wio7TIXz3v9cpvERGIp6LF6tfC 3Ws/w2epkFANtwCr7qac4IeIbQNoqU3eltzoWZlT5jAI12pCtBM4YHIACXBKdiJhyN 3eE40h0j90mxw== Date: Wed, 14 Jan 2026 18:58:51 +0200 From: Mike Rapoport To: Chris Mason , Pratyush Yadav Cc: Pasha Tatashin , jasonmiu@google.com, graf@amazon.com, dmatlack@google.com, rientjes@google.com, corbet@lwn.net, rdunlap@infradead.org, ilpo.jarvinen@linux.intel.com, kanie@linux.alibaba.com, ojeda@kernel.org, aliceryhl@google.com, masahiroy@kernel.org, akpm@linux-foundation.org, tj@kernel.org, yoann.congal@smile.fr, mmaurer@google.com, roman.gushchin@linux.dev, chenridong@huawei.com, axboe@kernel.dk, mark.rutland@arm.com, jannh@google.com, vincent.guittot@linaro.org, hannes@cmpxchg.org, dan.j.williams@intel.com, david@redhat.com, joel.granados@kernel.org, rostedt@goodmis.org, anna.schumaker@oracle.com, song@kernel.org, linux@weissschuh.net, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, gregkh@linuxfoundation.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, rafael@kernel.org, dakr@kernel.org, bartosz.golaszewski@linaro.org, cw00.choi@samsung.com, myungjoo.ham@samsung.com, yesanishhere@gmail.com, Jonathan.Cameron@huawei.com, quic_zijuhu@quicinc.com, aleksander.lobakin@intel.com, ira.weiny@intel.com, andriy.shevchenko@linux.intel.com, leon@kernel.org, lukas@wunner.de, bhelgaas@google.com, wagi@kernel.org, djeffery@redhat.com, stuart.w.hayes@gmail.com, ptyadav@amazon.de, lennart@poettering.net, brauner@kernel.org, linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, saeedm@nvidia.com, ajayachandra@nvidia.com, jgg@nvidia.com, parav@nvidia.com, leonro@nvidia.com, witu@nvidia.com, hughd@google.com, skhawaja@google.com, chrisl@kernel.org Subject: Re: [PATCH v8 14/18] mm: memfd_luo: allow preserving memfd Message-ID: References: <20251125165850.3389713-15-pasha.tatashin@soleen.com> <20260113140927.1074142-1-clm@meta.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260113140927.1074142-1-clm@meta.com> X-Rspamd-Queue-Id: 6F85AA0013 X-Stat-Signature: 1bqbmo7xgr3we4bf617jqrpjomfbbo5p X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1768409957-740953 X-HE-Meta: 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 8OpUxViW AWwqJcWlBxHZpLswLl6ttvC3W3NEIlS5KJCmMriHsKOaTgiY7OcFppp7CkNL5LxNfwP+V/iY6JSxuzX6mvDe8Cke//pqqY7NJYR+kXXexXI2Kkub8LLp+CmVVKADqyOwNRN1cR0cCWyYZKXUzcX/fbyYzEWsQ0IFk6iifcqTqOcx6XbTAcqB8q5OZpEvT3jarRn0OFTYQOtQO8tR/DxzxbrF2b+TGbtGe+2i9LlOEQJb+TLX7fDjar8BkQ7Vhd/oxkmO2J1mhMWo6Y9OntMxICWdqJREAexaiNfwLzeGm1D2Zc9bWKQ0Cr5WIPvuJonO4noxTnTQ4Y1dpUx4xCj0zQGBBoQqcJlIEWSS3X9J3gmisDHTpJNyLEsOzT+y4K/I2v3T5FnWjOlCyvFLgAN0B/7Gp/edEyHE6Exb3drmpPIy4DZieP2g/UIAucg== 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 Tue, Jan 13, 2026 at 06:09:23AM -0800, Chris Mason wrote: > On Tue, 25 Nov 2025 11:58:44 -0500 Pasha Tatashin wrote: > > Hi everyone, > > I'm running the v6.19 mm commits through patch review automation, and this > commit was flagged. I don't know this code well, but it looks like it > might be a real bug. > > [AI review output below] > > > diff --git a/mm/memfd_luo.c b/mm/memfd_luo.c > > new file mode 100644 > > index 0000000000000..4f6ba63b43105 > > --- /dev/null > > +++ b/mm/memfd_luo.c > > [ ... ] > > > +static int memfd_luo_retrieve_folios(struct file *file, > > + struct memfd_luo_folio_ser *folios_ser, > > + u64 nr_folios) > > +{ > > + struct inode *inode = file_inode(file); > > + struct address_space *mapping = inode->i_mapping; > > + struct folio *folio; > > + int err = -EIO; > > + long i; > > + > > + for (i = 0; i < nr_folios; i++) { > > [ ... ] > > > + err = shmem_add_to_page_cache(folio, mapping, index, NULL, > > + mapping_gfp_mask(mapping)); > > + if (err) { > > + pr_err("shmem: failed to add to page cache folio index %ld: %d\n", > > + i, err); > > + goto unlock_folio; > > + } > > + > > + if (flags & MEMFD_LUO_FOLIO_UPTODATE) > > + folio_mark_uptodate(folio); > > + if (flags & MEMFD_LUO_FOLIO_DIRTY) > > + folio_mark_dirty(folio); > > + > > + err = shmem_inode_acct_blocks(inode, 1); > > + if (err) { > > + pr_err("shmem: failed to account folio index %ld: %d\n", > > + i, err); > > + goto unlock_folio; > > + } > > When shmem_inode_acct_blocks() fails here, the folio has already been > added to the page cache by shmem_add_to_page_cache(). Should the folio be > removed from the page cache before going to unlock_folio? > > Looking at shmem_alloc_and_add_folio() in mm/shmem.c, when > shmem_inode_acct_blocks() fails after the folio has been added, it calls > filemap_remove_folio() to remove it: > > error = shmem_inode_acct_blocks(inode, pages); > if (error) { > ... > if (error) { > filemap_remove_folio(folio); > goto unlock; > } > } > > Without this, the folio remains in the page cache (counted in > mapping->nrpages) but info->alloced is not incremented (since > shmem_recalc_inode is not called). This could cause shmem accounting > inconsistency. My understanding that if anything fails in memfd_luo_retrieve_folios() the file is destroyed anyway and the accounting wouldn't matter. But to be on the safe side we should fix the error handling here. @Pratyush, what do you say? -- Sincerely yours, Mike.