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Received: from willy by casper.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1swMfm-000000080GV-3Jt3; Thu, 03 Oct 2024 14:19:18 +0000 Date: Thu, 3 Oct 2024 15:19:18 +0100 From: Matthew Wilcox To: Jan Kara Cc: Christian Brauner , linux-fsdevel@vger.kernel.org, ceph-devel@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-nilfs@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 1/6] fs: Move clearing of mappedtodisk to buffer.c Message-ID: References: <20241002040111.1023018-1-willy@infradead.org> <20241002040111.1023018-2-willy@infradead.org> <20241003121020.36i4ufbbuf4fbua7@quack3> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241003121020.36i4ufbbuf4fbua7@quack3> X-Rspam-User: X-Rspamd-Queue-Id: BF5EF20003 X-Rspamd-Server: rspam01 X-Stat-Signature: kke8jps77aaa1w186w48u8b7gk6z37zg X-HE-Tag: 1727965162-881668 X-HE-Meta: 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 CW115nba c3nqvY6IL1pwcBNqWWJYS/bxI4wU7NkVmxkuzHlZac5zaCdbyTVpuCRWRNrQmC6mWJ1LcuWNcG5HEZig39QRkuBW6y5Pu35sOVeRaHDxVUwn3MUZlXeXqsoR9LX/60V4dvB0mejktbF64Nc9wpiSfaY7/LGYwXts8M0JszyOpGtacKOHvgcGCV3aOl9iMgirMf0LbRWQzaMZTyqhPWAMw4GKVnGbgyeLmwwJ7+nM0b9WLvQ/MiRNzKnaadbWhiDRPbWzbWtBehlpPLzYVDQS1Lc1aOl0K256CQWol 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, Oct 03, 2024 at 02:10:20PM +0200, Jan Kara wrote: > On Wed 02-10-24 05:01:03, Matthew Wilcox (Oracle) wrote: > > The mappedtodisk flag is only meaningful for buffer head based > > filesystems. It should not be cleared for other filesystems. This allows > > us to reuse the mappedtodisk flag to have other meanings in filesystems > > that do not use buffer heads. > > > > Signed-off-by: Matthew Wilcox (Oracle) > > The patch looks good. But I'm bit confused about the changelog. There's no > generic code checking for mappedtodisk. Only nilfs2 actually uses it for > anything, all other filesystems just never look at it as far as my grepping > shows. So speaking about "filesystems that do not use buffer heads" looks > somewhat broad to me. Anyway feel free to add: Hmm. f2fs also uses it in page_mkwrite(). But it looks odd to me. Perhaps we could get rid of mappedtodisk entirely ... I see ext4 used to use it until someone removed it in 9ea7df534ed2 ;-) Anyway, what the changelog is trying to say is that only buffer-head filesystems ever have the mappedtodisk flag set, eg by block_read_full_folio() or do_mpage_readpage(). So it doesn't make sense to clear it for non-buffer-head filesystems, and may inhibit their ability to use it for unrelated purposes.