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[173.79.60.52]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-9087ff9d79bsm8203346d6.6.2026.08.04.11.47.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 04 Aug 2026 11:47:05 -0700 (PDT) Date: Tue, 4 Aug 2026 14:47:03 -0400 From: Gregory Price To: Matthew Wilcox Cc: Andrew Morton , Jane Chu , linux-mm@kvack.org, Muchun Song , Oscar Salvador , David Hildenbrand , Miaohe Lin , Naoya Horiguchi , Jan Kara , linux-fsdevel@vger.kernel.org, Christian Brauner , Jiaqi Yan Subject: Re: [PATCH v8 09/15] mm: Remove locking mf_mutex in is_raw_hwpoison_page_in_hugepage() Message-ID: References: <20260731200802.574821-1-willy@infradead.org> <20260731200802.574821-10-willy@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 9A38F14000A X-Rspam-User: X-Stat-Signature: 1acumrqi3pc7zcok5xghqckdj6tshjbo X-HE-Tag: 1785869226-8132 X-HE-Meta: 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 sUQgyFKG WXi7cO28LdocY6PK1s7Eco8fbd2DBwRYGC7BlBH1/AtlJ1dzjHIYOsGhaYho4++qB0+Dqn5XK33Ub0XPhHSqS/yS61s2oyEyL3bCsSUErwmsA+IQBCbxpbGml+9ieedT2TpjF+qlkiKMcw5RPY1Q5XM69pS3/mcMwGlyBHWGjsPSkIBTnvwpw9RUgGszSBbaXAdQizJ9I6kilk9YH914lV+ifizEtz1GWcEesHDUFyeruzHCwYfnuMAViQqaG+VWeuXpRF9X+8jd1pUPmA8+PAEVNzkW1gLfd6A6H/yaO2nxXOg/LIgDsLZdTBm9w9VRgwVzA29ijoMwSv5TFfme+enQhfdcKbkYyJvbY+mePKcLVSSFXZZIkhfas1+eyHDlmFC/5FZdR/UpgyVOB4WQux0eHZNj/SkEujCR1VBe+CWSDuzmM5vDkyiD5Jlo34NpOaZNoLc+KlROnabk= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Aug 04, 2026 at 05:58:26PM +0100, Matthew Wilcox wrote: > On Tue, Aug 04, 2026 at 12:36:00PM -0400, Gregory Price wrote: > > So we have all manner of protections that prevent us from taking this mutex > -- the folio must have a hwpoison page in it and must be hugetlb, but at > the end of the day, one can still be preempted while holding a mutex and > we never know when we might want to call this from a non-sleepable context. > > I'd be open to arguments that this should be an rwlock rather than > a spinlock. Or figure out a way to shard the lock per folio (lockdep > etc make it very hard to embed a spinlock in struct folio). I think > it'd also be profitable to change how we record poison for hugetlb to > not need locking or memory allocation. > I think such complexity needs to be driven by an actual demonstration the spinlock is problematic. It seems like if you're hitting devastating contention here, you have much bigger (hardware) problems. > But this is all a very long way from where I want to be working -- cleaning > up the page fault path. I think I've made a reasonable set of improvements > here, and somebody else can come along later to make the code even better. > Agreed. ~Gregory