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[34.124.168.21]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2d022bc6d70sm26178725ad.39.2026.07.30.05.05.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 30 Jul 2026 05:05:24 -0700 (PDT) Date: Thu, 30 Jul 2026 12:05:18 +0000 From: Pranjal Shrivastava To: Mike Rapoport Cc: Pasha Tatashin , Pratyush Yadav , Alexander Graf , Samiullah Khawaja , David Matlack , kexec@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 2/2] kho: Introduce preserve/restore APIs for high-order pages Message-ID: References: <20260723204203.2997395-1-praan@google.com> <20260723204203.2997395-3-praan@google.com> <178539640188.2151126.10266644348178621151.b4-review@b4> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <178539640188.2151126.10266644348178621151.b4-review@b4> X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: C7C274000E X-Stat-Signature: f17noyzarx66dzdmtzax65a5xti9hrpy X-Rspam-User: X-HE-Tag: 1785413126-792567 X-HE-Meta: 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 UrIfiy7P lCwRVyhamKNTwYqi7H6oeZFIM2jBr6oG40vAtLxW8Uvcc2BFtPpufpkbQ8+bJBvUysfPhqtyfzSctdOXGfhHG481e5pqHxjMJVzdGI1OTslwg5cScRbuOki6ATJg9czp9N55SQdQagTWEqHJyeCHd90H1UQb/jJzZaGxupFSjmoF4Ce/dYvQfnGaLDXS/qLsepNTdy8LlsEvIzmDFfobzAzCkWr8ZtSRaoxb2Ik4aqtvv7V2cwvEYRZxhV5cuOe9OVgo6EPdfd+Hc0bgU5JItZDSRY22As1q8yXse5BMGhZpL3lEldu0lnaurS7/QYzKW7Er3Ia8FwvaOWFgcP1JYUWjtcNjPsgn3EhCb Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Jul 30, 2026 at 10:26:41AM +0300, Mike Rapoport wrote: > Hi Pranjal, > > > The current KHO page preservation APIs (e.g. kho_preserve_pages) assume > > that multi-page blocks are split into independent 4KB pages during > > restoration. This is incompatible with high-order non-compound pages, > > such as DMA buffers, which must be restored with tail pages having a > > zero reference count. > > > > Introduce explicit preserve and restore APIs for high-order pages, > > which preserve and restore a high-order page block as a single unit, > > applying a refcount of 1 to the head page while leaving tail pages at 0. > > Rename the existing internal helper to __kho_restore_page() and > > consolidate the common restoration code into it. > > > > Signed-off-by: Pranjal Shrivastava > > > > @@ -457,10 +482,14 @@ struct page *kho_restore_pages(phys_addr_t phys, unsigned long nr_pages) > > while (pfn < end_pfn) { > > const unsigned int order = > > min(count_trailing_zeros(pfn), ilog2(end_pfn - pfn)); > > - struct page *page = kho_restore_page(PFN_PHYS(pfn), false); > > + unsigned int info_order; > > + struct page *page = __kho_restore_page(PFN_PHYS(pfn), &info_order); > > > > if (!page) > > return NULL; > > + > > + kho_init_pages(page, 1UL << info_order); > > + adjust_managed_page_count(page, 1UL << info_order); > > Seeing > > + adjust_managed_page_count(page, 1UL << info_order); > > for the third time hinted that something is off ;-) > Ack. I'll fold it into the __kho_restore_page() helper Thanks, Praan