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From: Baoquan He To: Nhat Pham Cc: linux-mm@kvack.org, akpm@linux-foundation.org, chrisl@kernel.org, kasong@tencent.com, baohua@kernel.org, youngjun.park@lge.com, hannes@cmpxchg.org, yosry@kernel.org, david@kernel.org, shikemeng@huaweicloud.com, chengming.zhou@linux.dev, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH 11/11] mm, swap: serialize xswap map/unmap with a mutex Message-ID: References: <20260727135029.1059441-1-baoquan.he@linux.dev> <20260727140503.1060918-1-baoquan.he@linux.dev> <20260727140503.1060918-10-baoquan.he@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Server: rspam03 X-Stat-Signature: sug7wh8sxxh3h7cx6dnq67sfb4hotixj X-Rspamd-Queue-Id: 4F33240005 X-HE-Tag: 1785917747-496259 X-HE-Meta: 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 ijyOxvXB v0YYVJkCPZfzA+VXp/ZYGctFvRUFXKatPCb0A9A1JcrgW9bMGd/A1avGb99iqPz2yXtDg+OOTtTj8GFPyjkFLIaqz04UylDs2sfMcGUVXiYklthqz5FH5VRJG+PMxx5tGebUY87fx+azKdXsnaufiKNJlDmw/cqqLcTooBDScTU/Sw21vvn47JkK42Lk1UlKfTYWMEUlxr3I3YvoH+DGnXgibdPMvmDVUOsO0YYHczg5rHw1nXf8N1E+4swvvoNq68etAZ28wrOJhc15hO8Ao0bJ7ng== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 07/27/26 at 08:13am, Nhat Pham wrote: > On Mon, Jul 27, 2026 at 7:06 AM Baoquan He wrote: > > > > Concurrent xswap grow operations race on vm_area_map_pages(), > > triggering WARN_ON(!pte_none) in the vmap page table walk when > > one thread sees a PTE already set by another. The -EBUSY safety > > net catches it but the warning is noisy and unavoidable without > > serialization. > > > > Add a per-device mutex (xswap_lock) held across xswap_map_clusters > > and xswap_unmap_clusters so that only one thread can modify the > > VM_SPARSE page table at a time. The shrink path is already > > deferred to a workqueue so it does not contend with itself. > > > > Signed-off-by: Baoquan He > > Seems like this should be squashed into one of the older patches, no? Both is fine to me, because putting it in a separate patch can get a specific log to describe it with more details. Have squashed it into patch 03 as suggested since they are small number of lines of change. Thanks Baoquan