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Received: from willy by casper.infradead.org with local (Exim 4.99.1 #2 (Red Hat Linux)) id 1x0KLH-0000000Gbt5-16nI; Sat, 29 Aug 2026 14:47:35 +0000 Date: Sat, 29 Aug 2026 15:47:35 +0100 From: Matthew Wilcox To: Wenjie Qi Cc: jack@suse.cz, akpm@linux-foundation.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, baohua@kernel.org, axboe@kernel.dk, trond.myklebust@hammerspace.com, qiwenjie@xiaomi.com Subject: Re: [PATCH v2] mm: filemap: retain mapped dropbehind folios Message-ID: References: <20260820142956.1414337-1-qiwenjie@xiaomi.com> <3fa43eaca792bc0bbde4b82a6c1fcdd3f528b398.1787999152.git.qiwenjie@xiaomi.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3fa43eaca792bc0bbde4b82a6c1fcdd3f528b398.1787999152.git.qiwenjie@xiaomi.com> X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 31F7EA0004 X-Stat-Signature: gnufupg91cqyu8fxp6p9dift6yowjg9i X-Rspam-User: X-HE-Tag: 1788014859-479232 X-HE-Meta: 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 K9X8GuRf NssUJuFBLTvFRwUVhbu4Ae2DvoFiXILxQs9IEcnSpeeW7fncxUjkeLzsU8ggshuwXtPxsOqhpaNPQMFm5PNotRfnYad70Uut7axqjGH7oozoujrP0VxOzZVsHviDV0ZnZKum44wPOgHDxuzrdFmygNXx1rD0fHv+HfJMGNzfThnWgtCuY48z57lWEnzaG44Y2qzHFbF7yeeXk8L3VkXA+vV9ev/b3ttDD2p31HPfH8xNYuFvTOdGjIcaVfg+1V8paO1zSEK1YdWhiQQpgKoGZ10cpnDpzVGq3MNIDzzEEE7ax0PFGPKRR68DuISh26FV3QB4//S4VUWOTxIQDO54X63XmxgKulZi9mWgc Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sat, Aug 29, 2026 at 08:30:47PM +0800, Wenjie Qi wrote: > From: Wenjie Qi > > Fault-around can map ready dropbehind folios without going through the > normal page-cache lookup that clears dropbehind. A mapping represents a > competing cached user, so retain the folio instead of forcibly unmapping it > when writeback completes. > > Unmapped dropbehind folios continue through the existing invalidation path. Yes, I think this is the right approach. Reviewed-by: Matthew Wilcox (Oracle)