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Received: from willy by casper.infradead.org with local (Exim 4.97.1 #2 (Red Hat Linux)) id 1rvMsd-00000009u94-2A0e; Fri, 12 Apr 2024 19:48:11 +0000 Date: Fri, 12 Apr 2024 20:48:11 +0100 From: Matthew Wilcox To: Miaohe Lin Cc: Jane Chu , Oscar Salvador , 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-Stat-Signature: km17a6r6byyunbixqgx6pwk49w7ie7gp X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 8C01D20016 X-Rspam-User: X-HE-Tag: 1712951474-801707 X-HE-Meta: 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 HUtq1SoC nr0QkJ8Lx7dy7l6xiDGPnl7KoQ4RzMiMUZL87rzKWHO1zj9cbYgW2zooCOcM1yo4WSlnNF0M+sP++JbJeAFup6ooz2n9lZZKHw5O2gm5ifNeZuQkdGb8fW53ahUMMmGShZ890ljhBKusSiGpUNRSR8V0T/kzOYe3b21skb2ppP1WGFhBqIeGus9wO1g== 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 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. > > /* > * We're only intended to deal with the non-Compound page here. > * However, the page could have changed compound pages due to > * race window. If this happens, we could try again to hopefully > * handle the page next round. > */ > if (PageCompound(p)) { > if (retry) { > ClearPageHWPoison(p); > unlock_page(p); > put_page(p); > flags &= ~MF_COUNT_INCREASED; > retry = false; > goto try_again; > } > res = action_result(pfn, MF_MSG_DIFFERENT_COMPOUND, MF_IGNORED); > goto unlock_page; > } > > So it might be better to replace above code block as WARN_ON(PageCompound(p)) and remove MF_MSG_DIFFERENT_COMPOUND case. > Any thoughts? Yes, I think you're right. As the MM handling of pages has evolved, people haven't kept memory-failure uptodate. That's both understandable and regrettable. I don't have the time to focus on memory-failure myself; I have a couple of hundred uses of page->mapping to eliminate. And I'd want to get a lot more serious about testing before starting on that journey. I do have ideas for handling hwpoison without splitting a folio. I'd also really like to improve memory-failure to handle sub-page-size blast radius (Intel CXL used to have a blast radius of 256 bytes). But realistically, these things are never going to rise high enough on my todo list to actually get done.