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b=G3D+otWkjpEuuOmYB9k6qKoX2/m1kh+SDQ8/IJ4U6pOo/FlflrGKj1i/87XmCGiCi lNqFQbBPR3mFs4hcxoCtX+7UxGvD5eReymZcVnxZVx5vfNUjrZeXu+jImmVMJT6Jql t6SsS16mOv/q7wbqnJSgjlnRBfKu7qHH3rIueFC4= Date: Fri, 8 May 2026 17:12:51 -0700 From: Andrew Morton To: Hao Ge Cc: Suren Baghdasaryan , Kent Overstreet , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v5] mm/alloc_tag: replace fixed-size early PFN array with dynamic linked list Message-Id: <20260508171251.9bfb5e833859090d4480e222@linux-foundation.org> In-Reply-To: <20260506022256.32664-1-hao.ge@linux.dev> References: <20260506022256.32664-1-hao.ge@linux.dev> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 6E33B18000B X-Rspam-User: X-Stat-Signature: spc1nrgf6nxiqhd6srdfja3879o1gqqc X-HE-Tag: 1778285573-917363 X-HE-Meta: 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 TasmTa+6 ZcGupHCDJl/zOpHlx0+D45U+osFEf9xFBEoY7Wfy4vq1ETUXvC/7uAhobmNaClBeWMRu+sRqF0neA/LMMt00BrMsP72sFwR0emhiWTOq51Hxl8nSQW1e5WNCDhRXQUTwhVHqfOyrh73EJbozqDgbII+P1dAaXdTph85hOH8EXwwmJXK31T/22MEdeBlSWx1fAeFmpUEbxcIv6julEXMfq8aNpGmq9qKOiyS9IKeoNXL6yEpySZi2VjcXVftkNsF0xkCMUcJD8a9NzwiEug4XFHHG0O4STQjlUft4+fSOAWjKoJWvCTL1suCNABLGStF056GJD4qNcfAaQWcWTOKnjjKZnbpZo15+gWI+9 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, 6 May 2026 10:22:56 +0800 Hao Ge wrote: > Pages allocated before page_ext is available have their codetag left > uninitialized. Track these early PFNs and clear their codetag in > clear_early_alloc_pfn_tag_refs() to avoid "alloc_tag was not set" > warnings when they are freed later. > > Currently a fixed-size array of 8192 entries is used, with a warning if > the limit is exceeded. However, the number of early allocations depends > on the number of CPUs and can be larger than 8192. > > Replace the fixed-size array with a dynamically allocated linked list > of pfn_pool structs. Each node is allocated via alloc_page() and mapped > to a pfn_pool containing a next pointer, an atomic slot counter, and a > PFN array that fills the remainder of the page. > > The tracking pages themselves are allocated via alloc_page(), which > would trigger __pgalloc_tag_add() -> alloc_tag_add_early_pfn() and > recurse indefinitely. Introduce __GFP_NO_CODETAG (reuses the > %__GFP_NO_OBJ_EXT bit) and pass gfp_flags through pgalloc_tag_add() > so that the early path can skip recording allocations that carry this > flag. AI review asked a couple of things. I have a feeling we saw at least one of these, so probably already dealt with. https://sashiko.dev/#/patchset/20260506022256.32664-1-hao.ge@linux.dev