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AJvYcCVmISij8d+OZCrhKl2XLMSe2TYysr8VD37om7C26c/KfG92zXbfVtPqMKMihYV8RUrz2VBYQ3v/Zw==@kvack.org X-Gm-Message-State: AOJu0YxBEsG9JTbjmf1MgxugB0duotjuPQbKho6j/FpXrGp3+wV3Aqvq UX8yIUwip/HD+We1S/p0JkTZeNp3PUagGfp85VRGfWq3mrVJ+t0mNAL+d7qRiJ+Lh+Ze7n0zr62 o3N18MU1L49FDtkLkKNkgkIDC7mU7aQ+UdhX9qTKCjQ== X-Gm-Gg: ASbGncu5+AngZsaU3DoJjPWkjCew5cADoHOa9iQBSINgHXJfsGWI36Tla1brYDot0S6 S/eKQoRG3bEfZ3ymOSnKmRBTk6fsybE45OlDs8kpiRZohaeX1Xmet4ZmAlA/K21hG0eWSgxCZnP T3iw1QhtPL7tSLzDdh3VBNUSp1c8ZtCw== X-Google-Smtp-Source: AGHT+IHrhwlhpbZgGn/INwXn8JABUEPnTpSZnLrw9spErvT2Y1rpItsFgRTQatYYH58STp3erxQD5FNgCdtGvUD856o= X-Received: by 2002:a05:622a:4ccf:b0:48a:2a08:cbef with SMTP id d75a77b69052e-49f4624f333mr3037761cf.5.1748023812162; Fri, 23 May 2025 11:10:12 -0700 (PDT) MIME-Version: 1.0 References: <20250515182322.117840-1-pasha.tatashin@soleen.com> <20250515182322.117840-9-pasha.tatashin@soleen.com> In-Reply-To: From: Pasha Tatashin Date: Fri, 23 May 2025 14:09:34 -0400 X-Gm-Features: AX0GCFsjdnMDiIp0JeLxLW-c2VjwkiovzqMTPqtMLc5iAfcnOak-tebCgQ6toto Message-ID: Subject: Re: [RFC v2 08/16] luo: luo_files: add infrastructure for FDs To: James Houghton Cc: pratyush@kernel.org, jasonmiu@google.com, graf@amazon.com, changyuanl@google.com, rppt@kernel.org, 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 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 039B3180002 X-Stat-Signature: 5jiz9izf1mb5kwd4j6dezwi3ch8oobkx X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1748023812-488494 X-HE-Meta: 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 sMdNNErN 7ZpAO1PN/KxyGHyGGFxewiSH8o6X/48BFTrcO8rMPudZZVAB2bXSmzlAO7h1pcvse++NLB3U96SBG5WVS+XIlod/yXa1MroL6GO+oF07V+xl4AG63+1zY2Se2jOlSjkpCWLcZSra3y9AKg8gltVdvsrupek//raVpXsuQbP7VfNUZb1IbEFgxtRlGnWWktm/OkkkLTqDmQTxv+dPKzjjluehd0OMYcf7TMLixe7PIl6oOAzn/6L4kZyWrZzLM9e4ssSKw1Tl8uqQO9GjJ+HfUoZntk/jYXP9JkWIBXSKZeWaASV8zUX4LVObca1lK8BgDPNNIy4w13GIMjIVOos+bII5od94DigKHKWCZSymEjhyurDh8uKugOFkGi8Sp7T6wB7QPrz5nbQVfX7IyJOrM0yT6VgViDs2bwocD4a24nu5oGzHcxg/9P74RYuArstwt+zo6rXw9VWuXP0Y= 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 Thu, May 15, 2025 at 7:16=E2=80=AFPM James Houghton wrote: > > On Thu, May 15, 2025 at 11:23=E2=80=AFAM Pasha Tatashin > wrote: > > +/** > > + * luo_retrieve_file - Find a registered file instance by its token. > > + * @token: The unique token of the file instance to retrieve. > > + * @file: Output parameter. On success (return value 0), this will poi= nt > > + * to the retrieved "struct file". > > + * > > + * Searches the global list for a &struct luo_file matching the @token= . Uses a > > + * read lock, allowing concurrent retrievals. > > + * > > + * Return: 0 on success. Negative errno on failure. > > + */ > > +int luo_retrieve_file(u64 token, struct file **file) > > +{ > > + struct luo_file *luo_file; > > + int ret =3D 0; > > + > > + luo_files_recreate_luo_files_xa_in(); > > + luo_state_read_enter(); > > + if (!liveupdate_state_updated()) { > > + pr_warn("File can be retrieved only in updated state\n"= ); > > + luo_state_read_exit(); > > + return -EBUSY; > > + } > > + > > + luo_file =3D xa_load(&luo_files_xa_in, token); > > + if (luo_file && !luo_file->reclaimed) { > > + luo_file->reclaimed =3D true; > > I haven't been able to pay too much attention to the series yet, and I > know this was posted as an RFC, so pardon my nit-picking. > > I think you need to have xchg here for this not to be racy, so something = like: > > `if (luo_file && !xchg(&luo_file->reclaimed, true))` > > Or maybe you meant to avoid this race some other way; IIUC, > luo_state_read_enter() is not sufficient. Thank you for catching this. This is a bug, I actually added a per fd mutex lock to struct luo_file that is supposed to be used here. I am going to address this in the next version. Thanks, Pasha > > Thanks! > > > + ret =3D luo_file->fs->retrieve(luo_file->fs->arg, > > + luo_file->private_data, > > + file); > > + if (!ret) > > + luo_file->file =3D *file; > > + } else if (luo_file && luo_file->reclaimed) { > > + pr_err("The file descriptor for token %lld has already = been retrieved\n", > > + token); > > + ret =3D -EINVAL; > > + } else { > > + ret =3D -ENOENT; > > + } > > + > > + luo_state_read_exit(); > > + > > + return ret; > > +}