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Miller" , "Andreas Larsson" , "Alexander Viro" , "Christian Brauner" , "Matthew Brost" , "Joshua Hahn" , "Rakie Kim" , "Byungchul Park" , "Gregory Price" , "Ying Huang" , "Alistair Popple" , "Chris Li" , "Kairui Song" , "Kemeng Shi" , "Nhat Pham" , "Baoquan He" , "Youngjun Park" , "Johannes Weiner" , "Qi Zheng" , "Shakeel Butt" , "Axel Rasmussen" , "Yuanchu Xie" , "Wei Xu" , "Chengming Zhou" , "Michal Hocko" , "Miklos Szeredi" , "Xu Xin" Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-usb@vger.kernel.org, linux-rdma@vger.kernel.org, selinux@vger.kernel.org, linux-sound@vger.kernel.org, bpf@vger.kernel.org, linux-scsi@vger.kernel.org, linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-trace-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, Linux-Arch , linux-fsdevel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linuxppc-dev@lists.ozlabs.org, kvm@vger.kernel.org, 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2Y/n0BdgL124YtqWKaIct6VseZzDvX1gOkU5Hh5fLZfVZx+ttOttf/Ka5JAbOoQXaMcO+uxmXF+zjge+eVL0JM+0DQaBbIML5j7ca7fbDmx2pjfbXRv2rHtcYBMe82jSRu6MjdTVcxvS5/wb9GtLMnmZpMKKX8Aoz8Xn/utzMsA/1riVqJjokWIty7Lrca1JVziTgMxvBNTZwBSlb54v8J8ho83VOcepd3VHA157Rit07fZcedy8dMd34Sir5yFFKew9G6N+L6+e1XkQRFdFG5cycUmEiIzUUdaZecCneCAMbiR1Lsc39QsFc41RNsV8YgT1T80c5vQ9kntJeU35nI Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Sep 17, 2026, at 18:22, Lorenzo Stoakes (ARM) wrote: > > mm/vma.c | 246 +++++++++++++++++++------- Hi Lorenzo, I see that in linux-next there is a new build failure in some configurations in code that you are changing here: mm/vma.c: In function '__mmap_region': mm/vma.c:3083:1: error: the frame size of 1552 bytes is larger than 1536 bytes [-Werror=frame-larger-than=] I don't immediately see anything that you did that would have introduced something bad that wasn't already there, so it's likely just gone from just below the limit I was using for my testing to just above. The 1536 byte limit is what I use on 64-bit builds with KASAN and otherwise still has a clean build (with a small number of local fixup patches). What I see is that this function has multiple structures on the stack that have nontrivial sizes: VMA_ITERATOR(vmi, mm, addr); /* 104 bytes */ MMAP_STATE(map, mm, &vmi, addr, len,...); /* 384 bytes */ struct vm_area_desc desc; /* 128 bytes */ The config that caused this is https://pastebin.com/raw/5M95qHy5, which is an x86-64 build with CONFIG_KASAN_STACK enabled, and likely a few other configuration options that made it a little worse. KASAN_STACK tends to double the stack size used by structures in order to catch out-of-bounds accesses. If I sprinkle some 'noinline_for_stack' annotations on functions called by __mmap_region(), I can get the size down to 1144 in this config, but that doesn't sound like a great workaround. The large stack usage is potentially harmful if this ends up in call chains that have additional large stack usage (e.g. kmalloc() leading to reclaim). Any ideas for how to reduce it here? Arnd