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Thu, 2 Oct 2025 12:10:11 +0100 Date: Thu, 2 Oct 2025 12:10:09 +0100 From: Jonathan Cameron To: Shivank Garg , CC: , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , Subject: Re: [RFC V3 5/9] mm: add support for copy offload for folio Migration Message-ID: <20251002121009.00005899@huawei.com> In-Reply-To: <20250923174752.35701-6-shivankg@amd.com> References: <20250923174752.35701-1-shivankg@amd.com> <20250923174752.35701-6-shivankg@amd.com> X-Mailer: Claws Mail 4.3.0 (GTK 3.24.42; x86_64-w64-mingw32) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.203.177.15] X-ClientProxiedBy: lhrpeml100012.china.huawei.com (7.191.174.184) To dubpeml100005.china.huawei.com (7.214.146.113) X-Rspamd-Queue-Id: 3D6031A0004 X-Rspamd-Server: rspam05 X-Stat-Signature: ya4mayws4y5aqiry6iwqwua93he4cezm X-Rspam-User: X-HE-Tag: 1759403415-911517 X-HE-Meta: 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 5df9W1U7 grJwLeq9/FWZJ2pFda8EHYdGSgX+q62PHFPqgosIUKf+/ULWY+azzBzhd4iPcjPEMsU4w+AZuvmVUuQN7V2v8GCGUPdDI9F1CjaY13Ih7vIG0SIUZPlBpZ7xhltOaf79MItYwfgo3nPdOWuBWMABpbvPnQXL8GG0UuSrfDQU7cElOZ+ImkAO7jBcOZ0PupLpv9jDwlOd/19hQiTKcuo9TpEkON39O7lw5wbBU2lslFThmXpHs2C2Soowu21NKsNYAzvNxFOLZEubsqjeYxVhB+oZGoDCp0caG5NoI7gABrCEuLfQRz1Q0v6kasJXFtABubgRvUdA8hdXr8XW3sVm/mkkizD054Q1tDC4J 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 Tue, 23 Sep 2025 17:47:40 +0000 Shivank Garg wrote: > From: Mike Day > > Offload-Copy drivers should implement following functions to enable folio > migration offloading: > migrate_offc() - This function takes src and dst folios list undergoing Trivial but I'd burn the characters to just spell out offc. migrate_offload_copy() isn't exactly long. > migration. It is responsible for transfer of page content between the > src and dst folios. > can_migrate_offc() - It performs necessary checks if offload copying > migration is supported for the give src and dst folios. > > Offload-Copy driver should include a mechanism to call start_offloading and > stop_offloading for enabling and disabling migration offload respectively. > > Signed-off-by: Mike Day > Co-developed-by: Shivank Garg > Signed-off-by: Shivank Garg Just a trivial comment inline. Ultimately feels like more complexity will be needed to deal with multiple providers of copying facilities being available, but I guess this works for now. Jonathan > diff --git a/mm/migrate_offc.c b/mm/migrate_offc.c > new file mode 100644 > index 000000000000..a6530658a3f7 > --- /dev/null > +++ b/mm/migrate_offc.c > @@ -0,0 +1,58 @@ > + > +struct migrator migrator = { > + .name = "kernel", > + .migrate_offc = folios_mc_copy, > + .srcu_head.func = srcu_mig_cb, > + .owner = NULL, No point in setting this to null explicitly unless intent is to act as some sort of documentation. > +}; > + > +int start_offloading(struct migrator *m) > +{ > + int offloading = 0; > + int ret; > + > + pr_info("starting migration offload by %s\n", m->name); > + ret = offc_update_migrator(m); > + if (ret < 0) { > + pr_err("failed to start migration offload by %s, err=%d\n", > + m->name, ret); > + return ret; > + } > + atomic_try_cmpxchg(&dispatch_to_offc, &offloading, 1); > + return 0; > +} > +EXPORT_SYMBOL_GPL(start_offloading); > + > +int stop_offloading(void) > +{ > + int offloading = 1; > + int ret; > + > + pr_info("stopping migration offload by %s\n", migrator.name); > + ret = offc_update_migrator(NULL); > + if (ret < 0) { > + pr_err("failed to stop migration offload by %s, err=%d\n", > + migrator.name, ret); > + return ret; > + } > + atomic_try_cmpxchg(&dispatch_to_offc, &offloading, 0); > + return 0; > +} > +EXPORT_SYMBOL_GPL(stop_offloading);