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Received: from 30.74.144.131(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0X162oXY_1776301370 cluster:ay36) by smtp.aliyun-inc.com; Thu, 16 Apr 2026 09:02:51 +0800 Message-ID: <760c048b-8da3-435b-a28f-fa8ec519cdc6@linux.alibaba.com> Date: Thu, 16 Apr 2026 09:02:50 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm: shmem: don't set large-order range for internal shmem mount To: Matthew Wilcox Cc: akpm@linux-foundation.org, hughd@google.com, ziy@nvidia.com, david@kernel.org, ljs@kernel.org, lance.yang@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: From: Baolin Wang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Stat-Signature: rf9df7rcisx8bnx4ndzk8cwhiq79wcg9 X-Rspamd-Queue-Id: 768881A0012 X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1776301374-900096 X-HE-Meta: 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 RtuevMOy HnwiNA+hezvEDLRAPm4Ejy8QTy1EYilQzdBB6Z59J6NiQRsICrpgKwhb9m48OfuEZTC0UaIN7Lw3ycyerxeAH+hCX12gFxIvmax6sPZHj6ERZomoYhfSOBlF97eTj+89+Bv5YKyBo1BlUwkMXAr2bIxzxujvgdR4qJcEfRJbpHA7DtftVNTuMTG9P9mHHG7zfZaSIVNFla3MrfwMsoZylKs+IafS2hPt3nB+qWtrLzWPBet4uYmYUIJXweWK3wIQHz5DBBnnajySmoWp+PZAldvb0b7VEY80p5RdM260i/z04buhLwzfL5mPI5PJ2VJrskV0ECEvW7LubVWIwMPxHq4TYeg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/15/26 9:45 PM, Matthew Wilcox wrote: > On Wed, Apr 15, 2026 at 04:22:53PM +0800, Baolin Wang wrote: >> + /* >> + * Only set the large order range for tmpfs mounts. The large order >> + * selection for the internal shmem mount is configured dynamically >> + * via the 'shmem_enabled' interfaces, so there is no need to set a >> + * large order range for the internal shmem mount's mapping. >> + * >> + * Note: Don't consider 'deny' for emergencies and 'force' for >> + * testing. >> + */ >> + if (sbinfo->huge && !(sb->s_flags & SB_KERNMOUNT)) >> mapping_set_large_folios(inode->i_mapping); > > This isn't how mapping_set_large_folios() is supposed to be used. > It's supposed to indicate "does the filesystem support large folios". > shmem should be setting it unconditionally and if there needs to be some > other way to prevent large folios from being created, we should do that > instead. As discussed with David, we’ve agreed that for anonymous shmem we should set mapping_set_large_folios() unconditionally. However, for tmpfs mounts, we should still respect the 'huge=' mount option. This was a previous performance fix, see commit 5a90c155defa ("tmpfs: don't enable large folios if not supported").