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b=QRqcfWwLVlutzlJWcd4eblfxvkeYGV3iLBwKV95VWeFGk2J41HWv4baV+wFuw4VbB pnt11u4k1tgYEBQv00NE1n70jfhHkmLi7ly6ZBfmLZEXbOT/xXPeUJIJ/aFIpsR0F/ ztICVLr2g32F9wQLjAPXTLUVtyWJoUMcixvJgNX6Ge4fVGm1ivQ/0IQLJj9D4pQMNQ 8n5ITpCgXMWKaYP+nkS0oawBOljImKzPm+ca7tAw6+CXV3sXltbHCrVPwY7qScXKJN Cb8+ZcVoGXuTIsl7tyT4BB7yFrtEcYbeVtfG7CqIHc7kGlQnU1Q/TiGI4Toa16ICvr AGbXCe5xaD+sg== From: Pratyush Yadav To: David Carlier Cc: Pasha Tatashin , Mike Rapoport , Pratyush Yadav , Andrew Morton , Chenghao Duan , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/memfd_luo: report error when restoring a folio fails mid-loop In-Reply-To: <20260415052300.362539-1-devnexen@gmail.com> (David Carlier's message of "Wed, 15 Apr 2026 06:23:00 +0100") References: <20260415052300.362539-1-devnexen@gmail.com> Date: Thu, 16 Apr 2026 09:44:37 +0000 Message-ID: <2vxzik9r6xyy.fsf@kernel.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 44ECF4000D X-Stat-Signature: fyad46deo5tje5kwxdcdckh4351yeuyz X-Rspam-User: X-HE-Tag: 1776332681-627241 X-HE-Meta: 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 GkxP81wr upnF6DmdqS1OvDQuJ7qCGNkIkrsHIAyZKZxIKBImWIfl1pKWiQlK3PQMGDnNnCOVPsbf/ZkRmmsiejBeI4Qp5qVhcUKyyuS054bQg1A6QF9FAJU5U54DvBst2f0Bdf5e/Vq1tkaHYkSxJAvo9673lkiIj2srfbtRFxDjkY0yhXvt/aE3DpaKdWPIW9eMAi89JBoUG6heEAGnP6MtTjkslFvRAyYALFjVkE7s3fymq4m9ZgOA9y1LiMK/0mx3nkgHRKKnY8kAK/frzqbw= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Apr 15 2026, David Carlier wrote: > memfd_luo_retrieve_folios() initialises err to -EIO, but the per-iteration > calls to mem_cgroup_charge(), shmem_add_to_page_cache() and > shmem_inode_acct_blocks() reuse and overwrite err. Once any iteration > completes successfully, err becomes zero. > > If a later iteration's kho_restore_folio() returns NULL, the failure path > jumps to put_folios without resetting err, so the function returns 0. > The caller memfd_luo_retrieve() then takes the success path, sets > args->file and reports the restore as successful, leaving userspace with > a partially populated memfd and no indication that anything went wrong. > > Set err to -EIO in the kho_restore_folio() failure branch so the error > is propagated to the caller. > > Signed-off-by: David Carlier Reviewed-by: Pratyush Yadav Please add these when applying: Cc: stable@vger.kernel.org Fixes: b3749f174d68 ("mm: memfd_luo: allow preserving memfd") [...] -- Regards, Pratyush Yadav