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Received: from willy by casper.infradead.org with local (Exim 4.97.1 #2 (Red Hat Linux)) id 1rutMv-00000006uwJ-01o8; Thu, 11 Apr 2024 12:17:29 +0000 Date: Thu, 11 Apr 2024 13:17:28 +0100 From: Matthew Wilcox To: Oscar Salvador Cc: Miaohe Lin , Jane Chu , linux-mm@kvack.org Subject: Re: [PATCH v2 07/11] mm/memory-failure: Convert memory_failure() to use a folio Message-ID: References: <20240408194232.118537-1-willy@infradead.org> <20240408194232.118537-8-willy@infradead.org> <2cc02f91-fbca-4160-9f31-bfb54f882f08@oracle.com> <1677b7a8-179d-4e4f-a7f3-5d6244586cdb@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 8415810000A X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: ntzaj795akt4u15qtpama9nhkf8jtspb X-HE-Tag: 1712837855-8499 X-HE-Meta: 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 kD7tF7mM MXHKauPJmssmA6VZqlu2WhCD3jolm80ShzkT/hThwSGqdxZverWvwNIWoWIJAm6s0K30yZvw5SnFAKhvGpOluBjQEFtb9VwlnqjYPVz/tp53qlYoKvmegrQYWAFCjGwidINBhbfWBlFRTxC3ftL/YGY4giVA8XaAEUfBOe/S7zyvkRwEa0b4SxM7O9zv4qzZSeAE6sOJsKKsDkUU= 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, Apr 11, 2024 at 01:23:43PM +0200, Oscar Salvador wrote: > On Thu, Apr 11, 2024 at 05:00:33PM +0800, Miaohe Lin wrote: > > But as code changes, the above page lock shift is gone. And I think below logic can't > > trigger now. As we hold extra page refcnt so page can't be coallesced into a new THP or Slab page. > > So I was wrong. > I did not check the slap part, but I did check the code that tries to > coallesce pages. > We have the following check in hpage_collapse_scan_pmd(): Even if that check succeeds, collapse_huge_page() works by allocating a new THP, copying the data into it and freeing the existing pages. It doesn't reassemble a THP in-place. I cannot find anywhere that will reassemble smaller folios into larger ones (other than the page allocator, and if you have a refcount on a folio, it can't possibly go into the page allocator).