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Wong" , linux-xfs@vger.kernel.org, willy@infradead.org, linux-mm@kvack.org Subject: Re: [PATCH 2/3] xfs: use folios in the buffer cache Message-ID: References: <20240118222216.4131379-1-david@fromorbit.com> <20240118222216.4131379-3-david@fromorbit.com> <20240119012624.GQ674499@frogsfrogsfrogs> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 6C74EA0007 X-Stat-Signature: mawu3z87u1q331z1a7ic1eonimz46id3 X-HE-Tag: 1705929561-628620 X-HE-Meta: U2FsdGVkX1+xgL5RHsjI5NpawP7DpOMxI8eSXjecrr1i/p6aNcGkqWdwS8CTWirw3woLXXPuGtnXyUA8O2+2cwyx8HLH1wqk/lxEllZCSyYHpDv5ZciHnECfCX4H5n47y32ah4DVZGolDjSLmOAok/0S0IesW89POGzhuj6IWjg+KFmVYKRnqZxeQuCym7idQuv0IJVS/+Z581m3npEVjrNVFsnBHazw3kel7y0yBMnqJmCaELws5myEhrtSVV6EsNDUdS9rHqJaqo5HYRMjZpW3U4FNnP61hu3W+2xXrvVgBqod7uNZgPRCmMoXAl7V+cE0KfjMCK2MERhtgeKfVR1rkqanet+q6PGPXCFTTJYv+mSrL5zqGuA5oAtFmPuDhuDCKkRo4JmBVtGwvz4u4b3Y1H2yyRG3AVhJLabmk4KhOi2LzNTQFpxZH1dNSKp1XnIbdUg/qnIfZgWlGDuq2cQlLUOdy/wG46RWu6Z9bkfSQKWwu4W2CEk/0c8OFJA9IZM87mh0uAkcVRzQZ6oFpnqekZqKsaMBY105myZCrC6JoxpdVAOmpuPv5UzoVgxa8ETmUE8ZIsV0tD45rNccxfnm++DoeRLKcEP2ET5FsXQXqbFuxOQm3ge4m1gEvkUIL9SsRHLqPL5ETt6fwWZao9YqL/cg6jGS6aRdVNic+1OQ1iUaV2OMDFltwizZkzWXe2BmG4hhAUNcyi64+Vj0xcrzJtHGSjhmsug24KXDyv2f960ahlxIKJsj73PYDquxppuoYAuMx7b4nQ0k6twowD47UXX4+MZZACEAA/vQ12QG7pf2JourEOXTLLfUKu9nitQ9NQPYNhetPGn/WD+sp7/pL3vrJZ8oa4SYZ04vgqp8VSs5I+vq0ZPs8mRUeXKaiea9DwgLGXHrge+l1G/GOPg+c/xj4XUhJUPxQMOtzwwb4twtcgtGsDd6JW8r6TWqWQPPP3RlpESEPVFE9iD xg7uV29m 2tTY9dSN+W7rQuXhbjwUqeOkGZSgK83ClEocJsn/i+EJ+48W3bYdWuZKZXNVMcv2iZChvNewkKesnGQzJEcTpGYxfG9bQ2YKtnZuMT0WCIihWG6Q= 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 Mon, Jan 22, 2024 at 11:05:20PM +1100, Dave Chinner wrote: > I haven't looked at what using vmalloc means for packing the buffer > into a bio - we currently use bio_add_page(), so does that mean we > have to use some variant of virt_to_page() to break the vmalloc > region up into it's backing pages to feed them to the bio? Or is > there some helper that I'm unaware of that does it all for us > magically? We have a kmem_to_page helper for chuking any kind of kernel virtual address space into pages. xfs_rw_bdev in fs/xfs/xfs_bio_io.c uses that for a bio, we should probably hav an async version of that and maybe move it to the block layer instead of duplicating the logic in various places. > Yeah, that's kind of where I'm going with this. Large folios already > turn off unmapped buffers, and I'd really like to get rid of that > page straddling mess that unmapped buffers require in the buffer > item dirty region tracking. That means we have to get rid of > unmapped buffers.... I actually have an old series to kill unmapped buffers and use vmalloc, but decided I'd need use folios for the fast path instead of paying the vmalloc overhead. I can dust it off and you can decide if you want to pick up parts of it.