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Thu, 04 Sep 2025 09:06:16 -0700 (PDT) MIME-Version: 1.0 References: <20250822192023.13477-1-ryncsn@gmail.com> <20250822192023.13477-2-ryncsn@gmail.com> In-Reply-To: From: Kairui Song Date: Fri, 5 Sep 2025 00:05:39 +0800 X-Gm-Features: Ac12FXxv3acge-iILq_OS5ASCS0n5qK1Bxoju9QuUQYOMxssZswBOiwQNaPmA3s Message-ID: Subject: Re: [PATCH 1/9] mm, swap: use unified helper for swap cache look up To: Nhat Pham Cc: linux-mm@kvack.org, Andrew Morton , Matthew Wilcox , Hugh Dickins , Chris Li , Barry Song , Baoquan He , Kemeng Shi , Baolin Wang , Ying Huang , Johannes Weiner , David Hildenbrand , Yosry Ahmed , Lorenzo Stoakes , Zi Yan , linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: E5A1810000A X-Stat-Signature: uuoixbrnyenwyqazu1dq5mqxn4bbi4kq X-HE-Tag: 1757001977-359918 X-HE-Meta: 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 i1J/1PIN oMn7WOvg/WzkOhgW1r4YYnF2QfUM106DAuAglxEO5Npgb3ThoEhAHAMaiQi7VLV7FRShSTypiZ4g0O1Gr868NnhBtVUaZda3ZT6FbxtKwvzCUIXYWklcGsiiHvW7r55YrHxCYhtRQ/hn13VMbJm3zyOZAipgZDkuAy3d1aghRzA8v1aL6XUaLsRKgSWN+OPm0s+H+2WQtFh0s7Gq9bD80lrSz0RXZO9WNML5AqW3av0b0qXCE7fZRKYnIJy78ZgjA7XF/VgHfTeyh18Hm2x7hBoq+9Jv0yn4osEK7yOoc17+JyphMyZjg8RubUP3Ku/hlfbgMg7RZ5aUOTHw5VxtPiLXFuGiNewcGqGOYAW4zD94+TwURL8/LT3gG+Jb6b61+zU0aBenjXF6OkrBZP/GEz7cLig== 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, Sep 4, 2025 at 2:10=E2=80=AFAM Nhat Pham wrote: > > On Fri, Aug 22, 2025 at 12:20=E2=80=AFPM Kairui Song w= rote: > > > > From: Kairui Song > > > > Always use swap_cache_get_folio for swap cache folio look up. The reaso= n > > we are not using it in all places is that it also updates the readahead > > info, and some callsites want to avoid that. > > > > So decouple readahead update with swap cache lookup into a standalone > > helper, let the caller call the readahead update helper if that's > > needed. And convert all swap cache lookups to use swap_cache_get_folio. > > > > After this commit, there are only three special cases for accessing swa= p > > cache space now: huge memory splitting, migration and shmem replacing, > > because they need to lock the Xarray. Following commits will wrap their > > accesses to the swap cache too with special helpers. > > > > Signed-off-by: Kairui Song > > My personal taste is we should have one patch to do the decoupling of > readahead update and the swapcache lookup, then another patch to use > the swapcache lookup helper in places that previously cannot be used > (due to the coupling of swapcache and readahead). > > But, this looks good to me :) Feel free to add: > > Acked-by: Nhat Pham > Thanks, I think I'll just drop the readahead update for now, it is harmless to keep it out of the lock and it's really small change, I didn't measure anything different either way. We may test and figure out how to read ahead better later, not really related to this series.