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b=RpqJH48RXTcs8FJSGZcYmrDP4K9N+qKoXv4m8p/2TWS+HFftLI2zUHPRkboBMdU5f oOTI8VTShKeZnIJZjA7ac1E137Vk8fnSFyO6rL1NHtW5B1vdbj+46jk+RErGgfQ+Mi lqkRtnHcFQM7OF5EeBTh6ujPIj+4VgAV9HaASwCKXSZeQs1l3om9o4mkfnXHXVI/aA OnKH07vr5Au18gKLXZjqXxUD9TCypvgp/3tFzXevu7YYnvLzRZz3prIYHh6NueDiqd tsF4U9xTAzAkusAt0gqBZQXL1CRUaDpBxVcvdA6DhYYi94dUB929jixXZ8BYKwRt4I L4SKEeopBx8WA== Message-ID: <07e26d39-6155-4661-b3df-c2419535ed43@kernel.org> Date: Mon, 20 Apr 2026 21:00:37 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3] mm: shmem: always support large folios for internal shmem mount To: Baolin Wang , akpm@linux-foundation.org, hughd@google.com Cc: willy@infradead.org, ziy@nvidia.com, ljs@kernel.org, lance.yang@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <26f954be62348591e720c4e8b7a9099b74dc1d6d.1776331555.git.baolin.wang@linux.alibaba.com> <1b3c0401-6d10-4a28-97c8-8e3858d8dc3d@kernel.org> <015de194-99b9-4f9e-8c89-d35807c6fd08@linux.alibaba.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: B1E7D40005 X-Rspamd-Server: rspam12 X-Stat-Signature: zsghftkrfgoc78dazby3ddmgwcw6zq7m X-Rspam-User: X-HE-Tag: 1776711643-960610 X-HE-Meta: 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 +ohzpM6q ikGJ2f06kgSMwmOXS0nR9hgv5CID1J2kPuNWcnFMkkuIsPQW9LKH0Ftr2thulNynC1sAhjHu0gNAR0pEOY54TkOUwhV+wp6JckIvZF0CNVM3IRm7QJsjjPJbOEBzo41r6aqSFzWELxbQ9uWFVbJbaRRp+s3DVlOFUS6B9pUMPgb2GWiHwoW1sdyX4Bmw1RM2em1180cbEhBhFHsXF5yjXcWosC64OBkorHlRKz0+F9xA6UolKTf4zNGvMLRDwrIC7orewvs3uyzW2NZFUPX2jwH8qrr0CG39HKKFzd6VP+lVHzps= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/17/26 14:45, Baolin Wang wrote: > > > On 4/17/26 5:52 PM, David Hildenbrand (Arm) wrote: >> On 4/17/26 11:27, Baolin Wang wrote: >>> >>> >>> >>> For tmpfs, yes. >> >> So, we could pass this check here, not setting >> mapping_set_large_folios(), but later someone toggles it and we missed >> to set mapping_set_large_folios()? > > Indeed. Good point. > >> >> Or would we always go through another __shmem_get_inode() after a >> remount? > > Not really. There could be files created before remount whose mappings > don't support large folios (with 'huge=never' option), while files > created after remount will have mappings that support large folios (if > remounted with 'huge=always' option). > > It looks like the previous commit 5a90c155defa was also problematic. The > huge mount option has introduced a lot of tricky issues:( > > Now I think Zi's previous suggestion should be able to clean up this > mess? That is, calling mapping_set_large_folios() unconditionally for > all shmem mounts, and revisiting Kefeng's first version to fix the > performance issue. Okay, so you'll send a patch to just set mapping_set_large_folios() unconditionally? > > [1] https://lore.kernel.org/all/20240914140613.2334139-1- > wangkefeng.wang@huawei.com/ Is that really required? Which call path would be the problematic bit with the above? I'd say, we'd check in the large folio allocation code whether ->huge is set to never instead? -- Cheers, David