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b=QKq5nN8K5ndy7CVhrqHocyNknrEreibYppmBdscgffzxuyIjIV5TCG8LqlefK6XODonbtusX6+zT7XDLT3YLwO7qFZTuhMDI+rqmx1Jp5sOwqZmGFFEQLjW5gXD8hAFJqdmG9ZnjOn5BdPnL9P7+KUxxUCZ1Bj2ilNf0mMJMBLw= Received: from localhost(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0WeVzfkj_1750667308 cluster:ay36) by smtp.aliyun-inc.com; Mon, 23 Jun 2025 16:28:29 +0800 From: Baolin Wang To: akpm@linux-foundation.org, hughd@google.com, david@redhat.com Cc: ziy@nvidia.com, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, baolin.wang@linux.alibaba.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH v3 2/2] mm: shmem: disallow hugepages if the system-wide shmem THP sysfs settings are disabled Date: Mon, 23 Jun 2025 16:28:09 +0800 Message-ID: <52bc87c7dbd362d4d2b7780e66c1536fe99454a0.1750666536.git.baolin.wang@linux.alibaba.com> X-Mailer: git-send-email 2.43.5 In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Queue-Id: B95E84000E X-Rspamd-Server: rspam10 X-Stat-Signature: bbgs1tshisu4znhrex5j88to74us74er X-HE-Tag: 1750667312-11879 X-HE-Meta: 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 7UxiHSOx CgFURVvBB12CVEtxnEsVnzKO3mIWhQ3gdxapAfEIxeu7ejo+n+7CFdFz9twun/Wq68pmBblrZd121kDOUYWG4gV6Z8g93sJ8+SecMNsgV5+9I5kuW/6DzbrRdiR5EZaHXdGbrZdODgpcsZ4D303AWujgQv94XpqQeqB6GUjHrZwThawQF4YD+KIyM9NiOpoYTNbPzgwajUG4aLzxa/YF1stzumce9n3FCjVGRhXtkZJVigtufkr+uvKMstlwzRK+YMbf53EtO1kTdDLL7dH++YOQs+eQwvtNezpWYKnlzUvXpb9Rci/1OTi3TIFJjocxax0Ro X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: When invoking thp_vma_allowable_orders(), if the TVA_ENFORCE_SYSFS flag is not specified, we will ignore the THP sysfs settings. And the MADV_COLLAPSE is an example of such a case. The MADV_COLLAPSE will ignore the system-wide shmem THP sysfs settings, which means that even though we have disabled the shmem THP configuration, MADV_COLLAPSE will still attempt to collapse into a shmem THP. This violates the rule we have agreed upon: never means never. Another rule for madvise, referring to David's suggestion: “allowing for collapsing in a VM without VM_HUGEPAGE in the "madvise" mode would be fine". To fix the MADV_COLLAPSE issue for shmem, then the current strategy should be: For shmem, if none of always, madvise, within_size, and inherit have enabled PMD-sized THP, then MADV_COLLAPSE will be prohibited from collapsing PMD-sized THP. For tmpfs, if the mount option is set with the 'huge=never' parameter, then MADV_COLLAPSE will be prohibited from collapsing PMD-sized THP. Meanwhile, we should fix the khugepaged selftest for shmem MADV_COLLAPSE by enabling shmem THP. Acked-by: Zi Yan Signed-off-by: Baolin Wang --- mm/shmem.c | 6 +++--- tools/testing/selftests/mm/khugepaged.c | 2 +- 2 files changed, 4 insertions(+), 4 deletions(-) diff --git a/mm/shmem.c b/mm/shmem.c index 2b19965d27df..e3f51fab2b7d 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -637,7 +637,7 @@ static unsigned int shmem_huge_global_enabled(struct inode *inode, pgoff_t index return 0; if (shmem_huge == SHMEM_HUGE_DENY) return 0; - if (shmem_huge_force || shmem_huge == SHMEM_HUGE_FORCE) + if (shmem_huge == SHMEM_HUGE_FORCE) return maybe_pmd_order; /* @@ -672,7 +672,7 @@ static unsigned int shmem_huge_global_enabled(struct inode *inode, pgoff_t index fallthrough; case SHMEM_HUGE_ADVISE: - if (vm_flags & VM_HUGEPAGE) + if (shmem_huge_force || (vm_flags & VM_HUGEPAGE)) return maybe_pmd_order; fallthrough; default: @@ -1806,7 +1806,7 @@ unsigned long shmem_allowable_huge_orders(struct inode *inode, /* Allow mTHP that will be fully within i_size. */ mask |= shmem_get_orders_within_size(inode, within_size_orders, index, 0); - if (vm_flags & VM_HUGEPAGE) + if (shmem_huge_force || (vm_flags & VM_HUGEPAGE)) mask |= READ_ONCE(huge_shmem_orders_madvise); if (global_orders > 0) diff --git a/tools/testing/selftests/mm/khugepaged.c b/tools/testing/selftests/mm/khugepaged.c index 85bfff53dba6..9517ed99c382 100644 --- a/tools/testing/selftests/mm/khugepaged.c +++ b/tools/testing/selftests/mm/khugepaged.c @@ -502,7 +502,7 @@ static void __madvise_collapse(const char *msg, char *p, int nr_hpages, printf("%s...", msg); settings.thp_enabled = THP_ALWAYS; - settings.shmem_enabled = SHMEM_NEVER; + settings.shmem_enabled = SHMEM_ALWAYS; thp_push_settings(&settings); /* Clear VM_NOHUGEPAGE */ -- 2.43.5