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Mon, 01 Sep 2025 16:51:09 -0700 (PDT) MIME-Version: 1.0 References: <20250822192023.13477-1-ryncsn@gmail.com> <20250822192023.13477-2-ryncsn@gmail.com> In-Reply-To: <20250822192023.13477-2-ryncsn@gmail.com> From: Barry Song <21cnbao@gmail.com> Date: Tue, 2 Sep 2025 07:50:57 +0800 X-Gm-Features: Ac12FXxqtGbLYCOlRJLl0vKc6QhZHbL5Ut-TDLRHKuwjm64bxLdZG0Cg3nR9zxY Message-ID: Subject: Re: [PATCH 1/9] mm, swap: use unified helper for swap cache look up To: Kairui Song Cc: linux-mm@kvack.org, Andrew Morton , Matthew Wilcox , Hugh Dickins , Chris Li , Baoquan He , Nhat Pham , 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-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: E5B564000A X-Stat-Signature: wixp85qjcfihqa834atisje9rfh4eo6m X-Rspam-User: X-HE-Tag: 1756770670-315751 X-HE-Meta: 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 KWQG2HDo PtnLEKwvnlESzEXuyfY+OMZlTd6AA2GnaCbIdkWwTrefZWkcc0HYEU9b3AS/THh7ZLlxQ5C/XMaEeKBpJ5LqUOQkp3K/RLz8RS/OmIE3BSBhzIX8XPWmY75+4lDYBZ7oy4Lc8EFEV+AZf7egR6DfQ49HQ5QkS6oiumhX5P/9NS7eYvK53Fbcdg2ZPp0J+keVjfZwPyMjTtgr3/tIJ6fwqjHAkzpPdwkkYVy0HsqGaRbyQDDpOI2YNlmDPwG62/DXFrrJACcc6y+YVsJtfgETgQ/eUOgCTDpt0jxu1/7YaEdnTxqQ19jZuCWt3PGzF2l4nDxkWu5v/EaGGPjHdVfvBpB0yDcfOuwVi/ZBKaAw3hEAjiawmMzsikUVFJYCpGBLWEPLDd+Elt5ecH2vqrms88dfOUhS225Dsy0BEWadoswA1niA= 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 Sat, Aug 23, 2025 at 3:20=E2=80=AFAM Kairui Song wrot= e: > > From: Kairui Song > > Always use swap_cache_get_folio for swap cache folio look up. The reason > 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 swap > 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 Nice! This has cleaned up the confusing mix of using swap_cache_get_folio with VMA, filemap_get_entry, swap_cache_get_folio without VMA, and filemap_get_folio. Reviewed-by: Barry Song Do we have any potential "dropbehind" cases for anonymous folios? I guess not for now. __filemap_get_folio() { if (folio_test_dropbehind(folio) && !(fgp_flags & FGP_DONTCACHE)) folio_clear_dropbehind(folio); } Can we mention something about it in the changelog? Best regards Barry