From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8DDBB3A4AD6; Wed, 14 Jan 2026 16:59:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768409956; cv=none; b=VQH0cNKaqP+ohCHLlLRW9H1lo8x04IpRk1sNRNqPK5lKzrZB8PFrhTIBGwjw7hsLmmn8VYWmJ1zek1tP6fKMkQmqHbBJ7KurlKhIOZ2ZBWR6u+b9p3xHqyYyFFCOFEFTst2KjashzkbA+K1yQH7IQW0mrCQJyKHXZVjE/57U4oU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768409956; c=relaxed/simple; bh=B0iF/dvyn/kec3053bYjCb0vU7YgriPK61h7HY9oPK0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=DyS6DKzFVo5grsJlZZxf2t8IADrF1HiKBF0tG07lhjikNjk9DuTHT7nYzQodDuyFjdQ1lDsq2YAbhCxLEBP9E7HV5O+vdWIkKSc3hLJ/8X+KABmoMqIprDkIDqxHiaVxnDavPJcyU9/G9EeF02nFoZxQnF6koiHtUKpJDRq3jjE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=r5rGUtxb; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="r5rGUtxb" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 84DD4C4CEF7; Wed, 14 Jan 2026 16:58:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1768409956; bh=B0iF/dvyn/kec3053bYjCb0vU7YgriPK61h7HY9oPK0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; 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> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260113140927.1074142-1-clm@meta.com> 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.