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[2.119.2.100]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-47f4635aa34sm3392720f8f.15.2026.07.13.17.26.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 13 Jul 2026 17:26:59 -0700 (PDT) Date: Tue, 14 Jul 2026 02:26:56 +0200 Message-ID: From: Hajime Tazaki To: daniel@thingy.jp Cc: ljs@kernel.org, akpm@linux-foundation.org, dhowells@redhat.com, linux-kernel@vger.kernel.org, sashiko-bot@kernel.org Subject: Re: [PATCH] ramfs: nommu: fix error rollback and reader races in ramfs_nommu_expand_for_mapping() In-Reply-To: References: <20260713115700.1349111-1-daniel@thingy.jp> User-Agent: Wanderlust/2.15.9 (Almost Unreal) Emacs/26.3 Mule/6.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII On Tue, 14 Jul 2026 01:36:21 +0200, Daniel Palmer wrote: > > > so I was wondering if it is still interesting to support the syscall > > (memfd_createfd) on nommu even the fcntl always fails. > > I think these fcntls will also fail on MMU=y where the full tmpfs is > not enabled for size reasons. I'm not sure if it's actually possible > to detect if tmpfs is really tmpfs or not. (I have this exact issue > with a test for nolibc). thanks, I'll look into detail. > memfd_createfd is still useful because it basically allows you to > create anonymous temporary files that you can pass to another process > and mmap() in both. > I use this for doing DNS resolution in my nolibc system: A process > that needs DNS resolution creates an memfd for the result and then > forks the resolver which mmap()s the memfd, fills in the result and > then exits. This avoids having the big resolver code in everything > that needs it since I don't have any shared libraries :). I understand, this might be a good test case with the actual use. > BTW: Could you share a link to your LTP fork? I will add it to my m68k > environment. forgive me in advance :) links are only the current working tree; it might be renamed/removed in future. here is a fork/branch of ltp: https://github.com/thehajime/ltp/tree/fix-nommu it is triggered from my UML branch with github actions (below), https://github.com/thehajime/linux/blob/zpoline-nommu-v6.10/.github/workflows/ci.yml using this dirty yaml file to build and execute part of testcases. https://github.com/thehajime/linux/blob/zpoline-nommu-v6.10/.github/workflows/ci-docker-build.yml -- Hajime