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Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1pedT1-00288y-DT; Tue, 21 Mar 2023 15:00:03 +0000 Date: Tue, 21 Mar 2023 15:00:03 +0000 From: Matthew Wilcox To: Hannes Reinecke Cc: linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 1/5] brd: convert to folios Message-ID: References: <20230306120127.21375-1-hare@suse.de> <20230306120127.21375-2-hare@suse.de> <76613838-fa4c-7f3e-3417-7a803fafc6c2@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 65DFE160040 X-Rspamd-Server: rspam09 X-Rspam-User: X-Stat-Signature: wm8at536nej8boa4wi4i66rxc1kj5c48 X-HE-Tag: 1679410810-917410 X-HE-Meta: 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 S1DGHo6L N0BGr6jsVMCpwb7pStvmT83hbJe0GniopM+8FzqC9i4losuQf4iURbh4meKqVOKeKxliutNHyd1QaienHTjKPFQNH7VgBYS3Lcdf52N47XPpGqBLbjwnkkPuNKMoRno+xhvC+hxwoVzqk4tGuna+zI5FePg== 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: On Tue, Mar 07, 2023 at 09:14:27AM +0100, Hannes Reinecke wrote: > On 3/7/23 08:30, Matthew Wilcox wrote: > > On Tue, Mar 07, 2023 at 07:55:32AM +0100, Hannes Reinecke wrote: > > > On 3/6/23 18:37, Matthew Wilcox wrote: > > > > On Mon, Mar 06, 2023 at 01:01:23PM +0100, Hannes Reinecke wrote: > > > > > - page = alloc_page(gfp | __GFP_ZERO | __GFP_HIGHMEM); > > > > > - if (!page) > > > > > + folio = folio_alloc(gfp | __GFP_ZERO, 0); > > > > > + if (!folio) > > > > > > > > Did you drop HIGHMEM support on purpose? > > > > > > No; I thought that folios would be doing that implicitely. > > > Will be re-adding. > > > > We can't ... not all filesystems want to allocate every folio from > > HIGHMEM. eg for superblocks, it often makes more sense to allocate the > > folio from lowmem than allocate it from highmem and keep it kmapped. > > The only GFP flag that folios force-set is __GFP_COMP because folios by > > definition are compound pages. > > Oh well. > > However, when playing with the modified brd and setting the logical&physical > blocksize to 16k the whole thing crashes > (not unexpectedly). > It does crash, however, in block_read_full_folio(), which rather > surprisingly (at least for me) is using create_page_buffers(); > I would have expected something like create_folio_buffers(). > Is this work in progress or what is the plan here? Supporting folios > PAGE_SIZE in blockdev is definitely still WIP. I know of at least one bug, which is: #define bh_offset(bh) ((unsigned long)(bh)->b_data & ~PAGE_MASK) That needs to be something like static size_t bh_offset(const struct buffer_head *bh) { return (unsigned long)bh->b_data & (folio_size(bh->b_folio) - 1); } I haven't done a thorough scan for folio-size problems in the block layer; I've just been fixing up things as I notice them. Yes, create_page_buffers() should now be create_folio_buffers(). Just didn't get round to it yet.