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AJvYcCXu80U4drbntxPO5S7RwU1ZVYJ0fQvE152WzrDSejNsC5YiPbmD5+Vl9cTlA/K07pXfEdh5LyiZE8c=@vger.kernel.org X-Gm-Message-State: AOJu0YzhZukcJGzIAf10Bq89DetGnIj9IOob0JaE79Tfc3HUdDxqPK61 wjPE8Mqhkhz4SyX64qj1yyqEQKgklHgCLF+2sbMF5cQrJULshM8QoxwEdT77PbZ6UBop3g2bBWa WF1jGEcQVsqPncBOcvrWyzdn+26+zUqHBYq2qxyygtg== X-Gm-Gg: ASbGncvaOmtAT5P548DdbOwBcWSqTwl1V0ceWf7sPWszFQaMeRh/NyJxFtoykCJgiAD vb1dWMsTNzvoA8fa2eWnUgxK1a5deewDTGmeEAklJvuEryvbiGyCjOrKoijrWsANECf6r4u+4Sg mgx5kBTWuhIiCXB+N3nNHV8U6OfgChmW+AJhejza3SK4qFVvjhj3lYHU9reNcQV6hu1tY29USUX kbX X-Google-Smtp-Source: AGHT+IHY/eg6lEzMqM6Ga55zC7XFq05s8YP913RvP8Vq9OFKOx955V1owXgBZfCIMqTYLUmetiFwFefB0L5EXnJijhY= X-Received: by 2002:a05:622a:99a:b0:4b2:9620:33b3 with SMTP id d75a77b69052e-4b31da1d546mr115573791cf.34.1756745692646; Mon, 01 Sep 2025 09:54:52 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20250807014442.3829950-1-pasha.tatashin@soleen.com> <20250807014442.3829950-30-pasha.tatashin@soleen.com> <20250826162019.GD2130239@nvidia.com> In-Reply-To: From: Pasha Tatashin Date: Mon, 1 Sep 2025 16:54:15 +0000 X-Gm-Features: Ac12FXwjvuuXLl4TYrvSYicUEdLVOyp0TZPBIDlFXyKegWX4ZiFbjlDKbUPVZr0 Message-ID: Subject: Re: [PATCH v3 29/30] luo: allow preserving memfd To: Mike Rapoport Cc: Jason Gunthorpe , pratyush@kernel.org, jasonmiu@google.com, graf@amazon.com, changyuanl@google.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, zhangguopeng@kylinos.cn, 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, parav@nvidia.com, leonro@nvidia.com, witu@nvidia.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Mon, Sep 1, 2025 at 4:23=E2=80=AFPM Mike Rapoport wrot= e: > > On Tue, Aug 26, 2025 at 01:20:19PM -0300, Jason Gunthorpe wrote: > > On Thu, Aug 07, 2025 at 01:44:35AM +0000, Pasha Tatashin wrote: > > > > > + /* > > > + * Most of the space should be taken by preserved folios. So take= its > > > + * size, plus a page for other properties. > > > + */ > > > + fdt =3D memfd_luo_create_fdt(PAGE_ALIGN(preserved_size) + PAGE_SI= ZE); > > > + if (!fdt) { > > > + err =3D -ENOMEM; > > > + goto err_unpin; > > > + } > > > > This doesn't seem to have any versioning scheme, it really should.. > > > > > + err =3D fdt_property_placeholder(fdt, "folios", preserved_size, > > > + (void **)&preserved_folios); > > > + if (err) { > > > + pr_err("Failed to reserve folios property in FDT: %s\n", > > > + fdt_strerror(err)); > > > + err =3D -ENOMEM; > > > + goto err_free_fdt; > > > + } > > > > Yuk. > > > > This really wants some luo helper > > > > 'luo alloc array' > > 'luo restore array' > > 'luo free array' > > We can just add kho_{preserve,restore}_vmalloc(). I've drafted it here: > https://git.kernel.org/pub/scm/linux/kernel/git/rppt/linux.git/log/?h=3Dk= ho/vmalloc/v1 The patch looks okay to me, but it doesn't support holes in vmap areas. While that is likely acceptable for vmalloc, it could be a problem if we want to preserve memfd with holes and using vmap preservation as a method, which would require a different approach. Still, this would help with preserving memfd. However, I wonder if we should add a separate preservation library on top of the kho and not as part of kho (or at least keep them in a separate file from core logic). This would allow us to preserve more advanced data structures such as this and define preservation version control, similar to Jason's store_object/restore_object proposal. > > Will wait for kbuild and then send proper patches. > > > -- > Sincerely yours, > Mike.