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Received: from willy by casper.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1tvIPt-0000000DaGw-1rwc; Thu, 20 Mar 2025 16:06:45 +0000 Date: Thu, 20 Mar 2025 16:06:45 +0000 From: Matthew Wilcox To: Bart Van Assche Cc: Luis Chamberlain , leon@kernel.org, hch@lst.de, kbusch@kernel.org, sagi@grimberg.me, axboe@kernel.dk, joro@8bytes.org, brauner@kernel.org, hare@suse.de, david@fromorbit.com, djwong@kernel.org, john.g.garry@oracle.com, ritesh.list@gmail.com, linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-mm@kvack.org, gost.dev@samsung.com, p.raghav@samsung.com, da.gomez@samsung.com, kernel@pankajraghav.com Subject: Re: [RFC 2/4] blkdev: lift BLK_MAX_BLOCK_SIZE to page cache limit Message-ID: References: <20250320111328.2841690-1-mcgrof@kernel.org> <20250320111328.2841690-3-mcgrof@kernel.org> <5459e3e0-656c-4d94-82c7-3880608f9ac8@acm.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5459e3e0-656c-4d94-82c7-3880608f9ac8@acm.org> X-Rspam-User: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 247A64001D X-Stat-Signature: z4txw8esyox51cidey1r5gqphxmq7may X-HE-Tag: 1742486819-740234 X-HE-Meta: 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 ERdwxrrd cWzQHn6/fWnvQL3Oa77TeEKx/DD8fD+lPEOjSpvMyWyRd6Gl57g2B+shP64P3uVXgMo6B/oNLUsHjzn8SZKDh4Mf/8xqznnd48nhyJFuLQFweFvCqnv5tvy8MC7fBA/taisNziIKGUevJxtVP2nAzVupwG4XCb+hL4r8NLzcx/mQJ3u3LQ2sKAI63J/RITZykAVBUmz4Vs+j+BebZxueSL2iGV/t3yYymI7TP8BfabrerEr5+TqSSCim/Mp5EoQy1LGQt4L5e5+9sp5B6fbU5qL9OiOdl8no/Zadysce+qA7VylfAEdi3RPqDulG9UbAoOhBcoLmzzxSX1ScOFP8THJLLNSw4BreGZPn/ 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, Mar 20, 2025 at 09:01:46AM -0700, Bart Van Assche wrote: > On 3/20/25 4:13 AM, Luis Chamberlain wrote: > > -/* > > - * We should strive for 1 << (PAGE_SHIFT + MAX_PAGECACHE_ORDER) > > - * however we constrain this to what we can validate and test. > > - */ > > -#define BLK_MAX_BLOCK_SIZE SZ_64K > > +#define BLK_MAX_BLOCK_SIZE 1 << (PAGE_SHIFT + MAX_PAGECACHE_ORDER) > > /* blk_validate_limits() validates bsize, so drivers don't usually need to */ > > static inline int blk_validate_block_size(unsigned long bsize) > > All logical block sizes above 4 KiB trigger write amplification if there > are applications that write 4 KiB at a time, isn't it? Isn't that issue > even worse for logical block sizes above 64 KiB? I think everybody knows this Bart. You've raised it before, we've talked about it, and you're not bringing anything new to the discussion this time. Why bring it up again?