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b=T7lLSbte1fabsTl8bqPNuY+WLRW6VPGciNfEAYPT0untF/dtC13lyqXaIO0GUsbnr XYTVpJJ5iSiIBpBoxy4cw6YQyaZpL+8tqyGQ8Um1dEpjQHgpXD8mWTKuV5TUacGD4V oJ735qQnfjo9RyoPMRCr0PXK0GeQdEC1wR80Tm/f9OCNJr+/bWfPJQAI134iqWkPly Z0K+i2IqKGqfKnpbqJ5B7sITRrsf3hZqa2a1UntZgvnAwrzBx52Ja0uDy8kHmCy9y8 2HxQdNUljStTVdpR6WtuwGU+mGKZQgJwNsmUIO7lNa5o58I0xDcvjxs1nzjJ2RHi92 YsuDksmPhh2Rg== Message-ID: <374a0a2a-444c-412b-8ab8-414dff6a2ca9@kernel.org> Date: Mon, 6 Jul 2026 15:47:43 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 2/8] mm: factor zone-device page init helpers out of __init_zone_device_page To: Li Zhe Cc: akpm@linux-foundation.org, apopple@nvidia.com, arnd@arndb.de, bp@alien8.de, dave.hansen@linux.intel.com, kees@kernel.org, linux-arch@vger.kernel.org, linux-hardening@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mingo@redhat.com, rppt@kernel.org, tglx@kernel.org, x86@kernel.org References: <38919e81-4c35-4e8b-ba2a-8af8be60b0b6@kernel.org> <20260706115035.49813-1-lizhe.67@bytedance.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 760B640003 X-Stat-Signature: 784mnq1ot1e36zstufunpajfj5xdjmu4 X-Rspam-User: X-HE-Tag: 1783345671-688647 X-HE-Meta: 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 fIHMfmQp T0tyVKHDGiEPhxuMq+eq4b0CwZZT53mYg15qwHI/9wlyxI1ueLm6wOewT7VSw2O5+oX2TGzPM3v9h26AGQ0ToonP4TWN3e5uh911X/YY+EFtCZJt/sIFVzCNStdM7HIEP+N1XbQ2CES/QcWvAMZmDYJheWQyMVSyVPqh0WuUIkYJ5Bl4qDR43dW3gn2mTKuOHHxoN3LFWTMPxRCWNjpDzHFikUve23sZNszEScCTOQKnppnYHohskddOS2nlMhMblmi92JNO3g40BLMMOEF2K3fCrfURirblk7zAWj/9n8RcMa5ZZ26euof8iGJ0NAnZpNqtK0vLuDKxb3js= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 7/6/26 13:50, Li Zhe wrote: > On Mon, Jul 6, 2026 at 11:13:45AM +0200, david@kernel.org wrote: > >>> +static inline bool pagemap_resets_refcount(const struct dev_pagemap *pgmap) >>> +{ >>> + /* >>> + * MEMORY_DEVICE_GENERIC pages regain a refcount of 1 in the free >>> + * path. The remaining ZONE_DEVICE types start from 0 here and raise >>> + * the count again when the allocator or driver hands the page out. >>> + */ >>> + switch (pgmap->type) { >>> + case MEMORY_DEVICE_FS_DAX: >>> + case MEMORY_DEVICE_PRIVATE: >>> + case MEMORY_DEVICE_COHERENT: >>> + case MEMORY_DEVICE_PCI_P2PDMA: >>> + return false; >>> + case MEMORY_DEVICE_GENERIC: >>> + return true; >>> + default: >>> + WARN_ONCE(1, "Unknown memory type!"); >>> + return true; >> >> Wouldn't the compiler warn if we would define a new type but forgot to update it >> here? We're using an enum, and I thought the compiler would bail out in that case. >> >> Or are we scared of some other garbage ending up in there? >> >> Apart from that LGTM. > > Thanks. > > I will drop the default case in v6 so a newly added enum memory_type > value is easier to catch during build review. > > I will move the WARN_ONCE() after the switch so we still keep a > runtime guard in case some invalid value ever shows up there. If the compiler complains, we won't need the WARN_ONCE(). -- Cheers, David