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a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1776242826; bh=YSYR/Ui/7QGCekywXf7bwFmRwPsJlsugZ+u5yIbM8+0=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=hINMi0D4FSTabBL82Z9bpaM7m8YRIafA7NzBoGo3uNQ8bli5dovabMELHuqbgX//n LEWdP5HdyZdwuuCcnHZqQnJ4cUooHstTvO24Tm4ydwqm47R7T9ljIx+OHQyvagbxTV UCzdW8aaSlPDtOwgbjfSA9SGeSyL4LH610VxllackL0IoQK2HVwxVR9ys1USFeKUzj KfpVcWO+ch4/G8XymgkgOTjsBi92rYmS3CpuhN+T+AxOzVF3HG4up6vBfjjPmiQjvs heAyxusbbvriJ2hh6BLBifUpLycwI1dP11fqvz0pimrJWGWaVO6ILRpqhaYmhmuijF rUVn+xAVvU8KQ== Message-ID: Date: Wed, 15 Apr 2026 10:47:00 +0200 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: 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: 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-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 9FB1816000B X-Stat-Signature: 9r581nraqrx6fx1jhijn3um7uh5k94qb X-HE-Tag: 1776242827-925827 X-HE-Meta: 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 M6sWjF/Y ApnHIuog5CKR5vMYNPVLy/2UGFqHc1aAX/sWDGXlkfwkuUDk9G12g48GyoWRga5L+n24q1YQPRS+5tMd6S0RcrNxdzbGrxv4iZmwfvNEKPKoZ11l5ndFmv/3qqFsoUsesrRZXgMZOSWvyfkIna7sjB1fryBYt0ijC8Eumv/gGFyVWfU5A0z/KyUjT5+JUGi0OEVxG1opEaiRXoFkKHaMjXkrssyMzVTGis2wDFQgAiZcF9FuE3EYVIDsN32uw4F1BQMdbli2lbr4H8BqibT0heX+3ethlEi7Cq5rC6bcBSS6Y6gQ= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/15/26 10:22, Baolin Wang wrote: > Anonymous shmem large order allocations are dynamically controlled via the > global THP sysfs knob (/sys/kernel/mm/transparent_hugepage/shmem_enabled) > and the per-size mTHP knobs (/sys/kernel/mm/transparent_hugepage/hugepages-kB/shmem_enabled). > > Therefore, anonymous shmem uses shmem_allowable_huge_orders() to check > which large orders are allowed, rather than relying on mapping_max_folio_order(). > Moreover, mapping_max_folio_order() is intended to control large order > allocations only for tmpfs mounts. Clarify this by not setting a large-order > range for internal shmem mount (e.g. anonymous shmem), to avoid confusion, > as discussed in the previous thread[1]. > > [1] https://lore.kernel.org/all/ec927492-4577-4192-8fad-85eb1bb43121@linux.alibaba.com/ > Signed-off-by: Baolin Wang > --- > Changes from v1: > - Update the comments and commit message, per Lance. > --- > mm/shmem.c | 12 ++++++++++-- > 1 file changed, 10 insertions(+), 2 deletions(-) > > diff --git a/mm/shmem.c b/mm/shmem.c > index 4ecefe02881d..568e1baee90d 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -3088,8 +3088,16 @@ static struct inode *__shmem_get_inode(struct mnt_idmap *idmap, > if (sbinfo->noswap) > mapping_set_unevictable(inode->i_mapping); > > - /* Don't consider 'deny' for emergencies and 'force' for testing */ > - if (sbinfo->huge) > + /* > + * 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); I don't like that special casing. In an ideal world, any mapping that supports large folios would indicate that. Now, which large folios to allocate is a different question. What's the problem with indicating for all shmem mappings that support large folios that support, but handling *which* folio sizes to allocate elsewhere? -- Cheers, David