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Fri, 12 Sep 2025 16:31:39 +0800 Message-ID: Date: Fri, 12 Sep 2025 16:31:38 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] mm: vmscan: remove folio_test_private() check in pageout() To: David Hildenbrand , akpm@linux-foundation.org, hannes@cmpxchg.org Cc: mhocko@kernel.org, zhengqi.arch@bytedance.com, shakeel.butt@linux.dev, lorenzo.stoakes@oracle.com, hughd@google.com, willy@infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <94cfb423-1dc5-43e1-bd1f-75b8d43fdc1a@redhat.com> From: Baolin Wang In-Reply-To: <94cfb423-1dc5-43e1-bd1f-75b8d43fdc1a@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 20DC940005 X-Stat-Signature: unnkjpk1fnfc7tuk4fnr1ha1axg85qhq X-HE-Tag: 1757665903-237245 X-HE-Meta: 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 5FXdHQ3G UKFI+Eqh+8NwFfwdRHIzq6NXUqwklEWMdIfwHgzVLwMfVRGCBqqoxZgjOKKeN77wCawRQhLcauSHLHwutz/XrcWQ/LcBIAihKerZMKcYpPDBWVf7iqNbdJLnMhNxCBW+qHMpDz5MOSuruifyyLXYFt6pLSgUy5mPdB80kDwJ9e4B59eZofevuu5q+ws+KCMAI/r9gtn1uu/76vrs3y8+XW3/hKAfhLebHOTjUYTv+1J2CurYM9L2cmB0jpv19hu53Hh5XK0zJ0ysGrK8IWLmMGM4D88ymE/V+FkoWtad8N1Du7BtEoAKhsyveFLSWlW2hosDAmAB2cSODeMxMmPj/UETAZn6bVS5dcNJ/uRD25z8GLAU= 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 2025/9/12 16:24, David Hildenbrand wrote: > On 12.09.25 10:24, David Hildenbrand wrote: >> On 12.09.25 05:45, Baolin Wang wrote: >>> Currently, we no longer attempt to write back filesystem folios in >>> pageout(), >>> and only tmpfs/shmem folios and anonymous swapcache folios can be >>> written back. >> >> Can you point me at the code where that is fenced off? Please see the following check in pageout(): if (!shmem_mapping(mapping) && !folio_test_anon(folio)) return PAGE_ACTIVATE; >> I can spot a folio_is_file_lru() check before we call it, but the >> description tells me that there are indeed ways we could still pass that >> check for file-lru folios if we are kswapd. Yes, but this also needs further cleanup, as kswapd also cannot reclaim filesystem dirty folios in pageout(). I plan to continue optimizing dirty file folios in isolate_lru_folios() to avoid some unnecessary scans. >>> Moreover, tmpfs/shmem and swapcache folios do not use the PG_private >>> flag, >>> which means no fs-private private data is used. Therefore, we can >>> remove the >>> redundant folio_test_private() checks and related buffer_head release >>> logic. >> >> If that's indeed the case, do we still need the folio_test_private() >> check in is_page_cache_freeable()? > > Ah, that's patch #2 :) >