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Received: from willy by casper.infradead.org with local (Exim 4.97.1 #2 (Red Hat Linux)) id 1senrb-00000002xhn-0v9J; Fri, 16 Aug 2024 03:42:55 +0000 Date: Fri, 16 Aug 2024 04:42:55 +0100 From: Matthew Wilcox To: David Hildenbrand Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [RFC] Merge PG_private_2 and PG_mappedtodisk Message-ID: References: <7e7ee391-6f4d-4d36-ace5-4f8ca81479bc@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <7e7ee391-6f4d-4d36-ace5-4f8ca81479bc@redhat.com> X-Stat-Signature: i9uc4i5cxhu7k3eaehbah8jscaxappte X-Rspam-User: X-Rspamd-Queue-Id: 9BEB840017 X-Rspamd-Server: rspam02 X-HE-Tag: 1723779780-221179 X-HE-Meta: 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 2SXUxjcl 056Nbqs2GZ11nnxhk/l/2A40dR94DLdJFh8ws8Kaq732iiVCaK4MJM20ZsfuUoTBSSG3beX/+9ZtHDDbJuVMYv6D85eBJdeHKuaaX3fFwjb3jRJnIN2Uw2FhQXKbpWrp80xyS92b9VuyRGg5GMrZCRIG8iuPE9g9arjdPB7ePIfWLntvER051YstwaGdgPH2qbIMg9wWaIFDG1W+UIyD2FD3niluETuIJWDKLnhmnGPuDrzYkMpFYUz5jManMc6hamGJi 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, Aug 15, 2024 at 11:41:23PM +0200, David Hildenbrand wrote: > On 14.08.24 19:36, Matthew Wilcox wrote: > > I believe these two flags have entirely disjoint uses and there will > > be no confusion in amalgamating them. > > > > Anonymous memory (re)uses mappedtodisk for anon_exclusive. > > Anonymous memory does not use PG_private_2. > > Also not when they are in the swapcache, right? Correct, swapcache has no use of PG_private_2. > > The one thing that's going to stand in the way of this is that various > > parts of the VFS treat private_2 as a "wait for this bit to be clear", > > due to its use in fscache (which is going away). > > > > So my approach here is going to be: > > > > - Rename mappedtodisk to be PG_owner_priv_2 (add appropriate aliases) > > - Switch btrfs to use owner_priv_2 instead of private_2 > > - Wait for the fscache use of private2 to finish its deprecation cycle > > - Remove private_2 entirely > > > > Sound good? > > Yes, one step into the right direction. Cool, thanks.