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Received: from willy by casper.infradead.org with local (Exim 4.99.1 #2 (Red Hat Linux)) id 1x8lQM-00000005Xnu-4A8c; Mon, 21 Sep 2026 21:19:43 +0000 Date: Mon, 21 Sep 2026 22:19:42 +0100 From: Matthew Wilcox To: "David Hildenbrand (Arm)" Cc: Andrew Morton , Jane Chu , linux-mm@kvack.org, Muchun Song , Oscar Salvador , Miaohe Lin , Naoya Horiguchi , Jan Kara , linux-fsdevel@vger.kernel.org, Christian Brauner , Jiaqi Yan Subject: Re: [PATCH v9 14/15] filemap: Add support for authoritative mappings Message-ID: References: <20260805210557.1118966-1-willy@infradead.org> <20260805210557.1118966-15-willy@infradead.org> <0e0a0908-8e5d-4cee-9fbb-ce730bb662e1@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0e0a0908-8e5d-4cee-9fbb-ce730bb662e1@kernel.org> X-Rspamd-Server: rspam04 X-Rspam-User: X-Stat-Signature: 7ng9px6xzsgmshaq77eghso3iarjb9qe X-Rspamd-Queue-Id: C325C1C0002 X-HE-Tag: 1790025586-1115 X-HE-Meta: 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 EUdhGth9 zF6Eo3K0nNNc3EdVtGK7VeMZqV7q/or/K8X4bxWZ/mf0poOgwuLeJFboESCShDch9IZAYKOSulr8Nj3fedwVh/3Xicn3pzuJvCGfj4ScgJ26GuHl3jRC0GmwZuc9PfPLwN34snJyeZdA0DdOcsThTpCCvQdxBtKveuNIuqgVIW3s+53c5VrFS+BmBczPDi+1T5SqCuaNbUUrFvrvO+AVpZXqNzAgAXinqeiI26gOWPvqGsHjD20AF0pAbTnDLzuJEbasyrrhWD+v5wKSHh/Z6c4jSVjyPV3c0DLA8sydIvMD1p2wcJWxPkQI8n8fXhceYzSzn1EUxInsBapFp9y5d7KgLOw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Sep 18, 2026 at 03:51:59PM +0200, David Hildenbrand (Arm) wrote: > On 8/5/26 23:05, Matthew Wilcox (Oracle) wrote: > > +++ b/include/linux/pagemap.h > > @@ -210,6 +210,7 @@ enum mapping_flags { > > AS_WRITEBACK_MAY_DEADLOCK_ON_RECLAIM = 9, > > AS_KERNEL_FILE = 10, /* mapping for a fake kernel file that shouldn't > > account usage to user cgroups */ > > + AS_AUTHORITATIVE = 11, /* If we miss in the page cache, it's a hole */ > > Just curious if "in-memory file system" would be a different way of looking at > it. There, a hole in the page cache always expresses a hole in the file. > > AS_IN_MEMORY_FILE > > Just an idea, because that's why I always had in mind regarding that (all state > in memory). I suspect that's always going to be the case, but I don't want to be quite so prescriptive. I'd rather describe the property than the user.