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Received: from willy by casper.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1uBwzo-0000000Blxx-3hzM; Mon, 05 May 2025 14:40:40 +0000 Date: Mon, 5 May 2025 15:40:40 +0100 From: Matthew Wilcox To: Christoph Hellwig Cc: Luis Chamberlain , brauner@kernel.org, akpm@linux-foundation.org, 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 Subject: Re: [PATCH] swapfile: disable swapon for bs > ps devices Message-ID: References: <20250502231309.766016-1-mcgrof@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 0569B140014 X-Stat-Signature: wo4kgrymz3udr95iyg7itp5abs481mt7 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1746456045-820439 X-HE-Meta: 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 l6MFgwmY 4GT4vHFNIUIsRfJA20Qp0KoWryrptNO1TQ78+ujOWz1B8eJvbUEE1lLglODPsA0w8KSMg+GMZgVQYfN5tVxUVWtuEUTtyqTrdTzO9dorjbyIf/2OxY+l1+z0C0z9ZhWsgaKaP7B27cwTBbQvJoGC6+y6vvnPDv6+8qAaoPRi8HDLY9i5NjXgDH2BWzFPPtOWe0lTqvUBloZfsqiQxg8T4i/WyDzIN3bQ3coJx3pvaVVorxME= 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 Sun, May 04, 2025 at 11:25:11PM -0700, Christoph Hellwig wrote: > On Fri, May 02, 2025 at 04:13:09PM -0700, Luis Chamberlain wrote: > > Devices which have a requirement for bs > ps cannot be supported for > > swap as swap still needs work. > > This should work just fine for swap through intelligent enough file > systems not using the generic ->bmap based swap path, although > performance would still be horrible. "intelligent enough" is doing a lot of heavy lifting there. Setting aside that only netfs (nfs and cifs) implement ->swap_rw today, a block fs which wanted to support sub-block-size swap accesses would need to pad writes (not a huge problem), but on reads, it'd need to either discard the extra data somewhere or (better) bring the other pages into the swap cache. Really, I think it needs a major rethink of the swap system, which is happening anyway.