From: Zi Yan <ziy@nvidia.com>
To: Andrew Morton <akpm@linux-foundation.org>,
David Hildenbrand <david@kernel.org>,
"Matthew Wilcox (Oracle)" <willy@infradead.org>,
Song Liu <songliubraving@fb.com>
Cc: Chris Mason <clm@fb.com>, David Sterba <dsterba@suse.com>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Christian Brauner <brauner@kernel.org>, Jan Kara <jack@suse.cz>,
Lorenzo Stoakes <ljs@kernel.org>, Zi Yan <ziy@nvidia.com>,
Baolin Wang <baolin.wang@linux.alibaba.com>,
"Liam R. Howlett" <Liam.Howlett@oracle.com>,
Nico Pache <npache@redhat.com>,
Ryan Roberts <ryan.roberts@arm.com>, Dev Jain <dev.jain@arm.com>,
Barry Song <baohua@kernel.org>, Lance Yang <lance.yang@linux.dev>,
Vlastimil Babka <vbabka@kernel.org>,
Mike Rapoport <rppt@kernel.org>,
Suren Baghdasaryan <surenb@google.com>,
Michal Hocko <mhocko@suse.com>, Shuah Khan <shuah@kernel.org>,
linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
linux-kselftest@vger.kernel.org,
Liam Howlett <liam@infradead.org>
Subject: [PATCH v6 01/14] mm/khugepaged: remove READ_ONLY_THP_FOR_FS check
Date: Sun, 17 May 2026 09:54:03 -0400 [thread overview]
Message-ID: <20260517135416.1434539-2-ziy@nvidia.com> (raw)
In-Reply-To: <20260517135416.1434539-1-ziy@nvidia.com>
collapse_file() requires FSes supporting large folio with at least
PMD_ORDER, so replace the READ_ONLY_THP_FOR_FS check with that.
MADV_COLLAPSE ignores shmem huge config, so exclude the check for shmem.
While at it, replace VM_BUG_ON with VM_WARN_ON_ONCE.
Add a helper function mapping_pmd_folio_support() for FSes supporting
large folio with at least PMD_ORDER.
Signed-off-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Lance Yang <lance.yang@linux.dev>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Nico Pache <npache@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Barry Song <baohua@kernel.org>
Cc: Chris Mason <clm@fb.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Sterba <dsterba@suse.com>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Liam Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
---
include/linux/pagemap.h | 27 +++++++++++++++++++++++++++
mm/khugepaged.c | 10 ++++++++--
2 files changed, 35 insertions(+), 2 deletions(-)
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 1f50991b43e3b..308d846531d03 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -513,6 +513,33 @@ static inline bool mapping_large_folio_support(const struct address_space *mappi
return mapping_max_folio_order(mapping) > 0;
}
+/**
+ * mapping_pmd_folio_support() - Check if a mapping supports PMD-sized folio
+ * @mapping: The address_space
+ *
+ * While some mappings support large folios, they might not support PMD-sized
+ * folios. This function checks whether a mapping supports PMD-sized folios.
+ * For example, khugepaged needs this information before attempting to
+ * collapsing THPs.
+ *
+ * Return: True if PMD-sized folios are supported, otherwise false.
+ */
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+static inline bool mapping_pmd_folio_support(const struct address_space *mapping)
+{
+ /* AS_FOLIO_ORDER is only reasonable for pagecache folios */
+ VM_WARN_ON_ONCE((unsigned long)mapping & FOLIO_MAPPING_ANON);
+
+ return mapping_min_folio_order(mapping) <= PMD_ORDER &&
+ mapping_max_folio_order(mapping) >= PMD_ORDER;
+}
+#else
+static inline bool mapping_pmd_folio_support(const struct address_space *mapping)
+{
+ return false;
+}
+#endif
+
/* Return the maximum folio size for this pagecache mapping, in bytes. */
static inline size_t mapping_max_folio_size(const struct address_space *mapping)
{
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 5ba298d420b74..afd61168d915c 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -2243,8 +2243,14 @@ static enum scan_result collapse_file(struct mm_struct *mm, unsigned long addr,
int nr_none = 0;
bool is_shmem = shmem_file(file);
- VM_BUG_ON(!IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && !is_shmem);
- VM_BUG_ON(start & (HPAGE_PMD_NR - 1));
+ /*
+ * MADV_COLLAPSE ignores shmem huge config, so do not check shmem
+ *
+ * TODO: once shmem always calls mapping_set_large_folios() on its
+ * mapping, the shmem check can be removed.
+ */
+ VM_WARN_ON_ONCE(!is_shmem && !mapping_pmd_folio_support(mapping));
+ VM_WARN_ON_ONCE(start & (HPAGE_PMD_NR - 1));
result = alloc_charge_folio(&new_folio, mm, cc, HPAGE_PMD_ORDER);
if (result != SCAN_SUCCEED)
--
2.53.0
next prev parent reply other threads:[~2026-05-17 13:55 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-17 13:54 [PATCH v6 00/14] Remove CONFIG_READ_ONLY_THP_FOR_FS and enable file THP for writable files Zi Yan
2026-05-17 13:54 ` Zi Yan [this message]
2026-05-17 13:54 ` [PATCH v6 02/14] mm/khugepaged: add folio dirty check after try_to_unmap() Zi Yan
2026-05-17 13:54 ` [PATCH v6 03/14] mm/huge_memory: remove READ_ONLY_THP_FOR_FS from file_thp_enabled() Zi Yan
2026-05-17 13:54 ` [PATCH v6 04/14] mm/khugepaged: remove READ_ONLY_THP_FOR_FS check in hugepage_enabled() Zi Yan
2026-05-17 13:54 ` [PATCH v6 05/14] mm: remove READ_ONLY_THP_FOR_FS Kconfig option Zi Yan
2026-05-17 13:54 ` [PATCH v6 06/14] mm: fs: remove filemap_nr_thps*() functions and their users Zi Yan
2026-05-17 13:54 ` [PATCH v6 07/14] fs: remove nr_thps from struct address_space Zi Yan
2026-05-17 13:54 ` [PATCH v6 08/14] mm/huge_memory: remove folio split check for READ_ONLY_THP_FOR_FS Zi Yan
2026-05-17 13:54 ` [PATCH v6 09/14] mm/truncate: use folio_split() in truncate_inode_partial_folio() Zi Yan
2026-05-17 13:54 ` [PATCH v6 10/14] fs/btrfs: remove a comment referring to READ_ONLY_THP_FOR_FS Zi Yan
2026-05-17 13:54 ` [PATCH v6 11/14] selftests/mm: remove READ_ONLY_THP_FOR_FS in khugepaged Zi Yan
2026-05-17 13:54 ` [PATCH v6 12/14] selftests/mm: remove READ_ONLY_THP_FOR_FS code from guard-regions Zi Yan
2026-05-17 13:54 ` [PATCH v6 13/14] mm/khugepaged: enable clean pagecache folio collapse for writable files Zi Yan
2026-05-17 13:54 ` [PATCH v6 14/14] selftests/mm: add writable-file collapse tests for khugepaged Zi Yan
2026-05-18 22:21 ` [PATCH v6 00/14] Remove CONFIG_READ_ONLY_THP_FOR_FS and enable file THP for writable files Andrew Morton
2026-05-18 23:39 ` Zi Yan
2026-05-19 0:45 ` Andrew Morton
2026-05-19 0:59 ` Zi Yan
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