* + mm-fs-remove-filemap_nr_thps-functions-and-their-users.patch added to mm-new branch
@ 2026-04-24 10:31 Andrew Morton
0 siblings, 0 replies; 2+ messages in thread
From: Andrew Morton @ 2026-04-24 10:31 UTC (permalink / raw)
To: mm-commits, ziy, akpm
The patch titled
Subject: mm: fs: remove filemap_nr_thps*() functions and their users
has been added to the -mm mm-new branch. Its filename is
mm-fs-remove-filemap_nr_thps-functions-and-their-users.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-fs-remove-filemap_nr_thps-functions-and-their-users.patch
This patch will later appear in the mm-new branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews. Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.
The mm-new branch of mm.git is not included in linux-next
If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via various
branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there most days
------------------------------------------------------
From: Zi Yan <ziy@nvidia.com>
Subject: mm: fs: remove filemap_nr_thps*() functions and their users
Date: Thu, 23 Apr 2026 22:49:09 -0400
They are used by READ_ONLY_THP_FOR_FS to handle writes to FSes without
large folio support, so that read-only THPs created in these FSes are not
seen by the FSes when the underlying fd becomes writable. Now read-only
PMD THPs only appear in a FS with large folio support and the supported
orders include PMD_ORDRE.
READ_ONLY_THP_FOR_FS was using mapping->nr_thps, inode->i_writecount, and
smp_mb() to prevent writes to a read-only THP and collapsing writable
folios into a THP. In collapse_file(), mapping->nr_thps is increased,
then smp_mb(), and if inode->i_writecount > 0, collapse is stopped, while
do_dentry_open() first increases inode->i_writecount, then a full memory
fence, and if mapping->nr_thps > 0, all read-only THPs are truncated.
Now this mechanism can be removed along with READ_ONLY_THP_FOR_FS code,
since a dirty folio check has been added after try_to_unmap() in
collapse_file() to make sure no writable folio can be collapsed.
Link: https://lore.kernel.org/20260424024915.28758-7-ziy@nvidia.com
Signed-off-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.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: Lance Yang <lance.yang@linux.dev>
Cc: Liam Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nico Pache <npache@redhat.com>
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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
fs/open.c | 27 ---------------------------
include/linux/pagemap.h | 29 -----------------------------
mm/filemap.c | 1 -
mm/huge_memory.c | 1 -
mm/khugepaged.c | 28 ----------------------------
5 files changed, 86 deletions(-)
--- a/fs/open.c~mm-fs-remove-filemap_nr_thps-functions-and-their-users
+++ a/fs/open.c
@@ -968,33 +968,6 @@ static int do_dentry_open(struct file *f
if ((f->f_flags & O_DIRECT) && !(f->f_mode & FMODE_CAN_ODIRECT))
return -EINVAL;
- /*
- * XXX: Huge page cache doesn't support writing yet. Drop all page
- * cache for this file before processing writes.
- */
- if (f->f_mode & FMODE_WRITE) {
- /*
- * Depends on full fence from get_write_access() to synchronize
- * against collapse_file() regarding i_writecount and nr_thps
- * updates. Ensures subsequent insertion of THPs into the page
- * cache will fail.
- */
- if (filemap_nr_thps(inode->i_mapping)) {
- struct address_space *mapping = inode->i_mapping;
-
- filemap_invalidate_lock(inode->i_mapping);
- /*
- * unmap_mapping_range just need to be called once
- * here, because the private pages is not need to be
- * unmapped mapping (e.g. data segment of dynamic
- * shared libraries here).
- */
- unmap_mapping_range(mapping, 0, 0, 0);
- truncate_inode_pages(mapping, 0);
- filemap_invalidate_unlock(inode->i_mapping);
- }
- }
-
return 0;
cleanup_all:
--- a/include/linux/pagemap.h~mm-fs-remove-filemap_nr_thps-functions-and-their-users
+++ a/include/linux/pagemap.h
@@ -528,35 +528,6 @@ static inline size_t mapping_max_folio_s
return PAGE_SIZE << mapping_max_folio_order(mapping);
}
-static inline int filemap_nr_thps(const struct address_space *mapping)
-{
-#ifdef CONFIG_READ_ONLY_THP_FOR_FS
- return atomic_read(&mapping->nr_thps);
-#else
- return 0;
-#endif
-}
-
-static inline void filemap_nr_thps_inc(struct address_space *mapping)
-{
-#ifdef CONFIG_READ_ONLY_THP_FOR_FS
- if (!mapping_large_folio_support(mapping))
- atomic_inc(&mapping->nr_thps);
-#else
- WARN_ON_ONCE(mapping_large_folio_support(mapping) == 0);
-#endif
-}
-
-static inline void filemap_nr_thps_dec(struct address_space *mapping)
-{
-#ifdef CONFIG_READ_ONLY_THP_FOR_FS
- if (!mapping_large_folio_support(mapping))
- atomic_dec(&mapping->nr_thps);
-#else
- WARN_ON_ONCE(mapping_large_folio_support(mapping) == 0);
-#endif
-}
-
struct address_space *folio_mapping(const struct folio *folio);
/**
--- a/mm/filemap.c~mm-fs-remove-filemap_nr_thps-functions-and-their-users
+++ a/mm/filemap.c
@@ -189,7 +189,6 @@ static void filemap_unaccount_folio(stru
lruvec_stat_mod_folio(folio, NR_SHMEM_THPS, -nr);
} else if (folio_test_pmd_mappable(folio)) {
lruvec_stat_mod_folio(folio, NR_FILE_THPS, -nr);
- filemap_nr_thps_dec(mapping);
}
if (test_bit(AS_KERNEL_FILE, &folio->mapping->flags))
mod_node_page_state(folio_pgdat(folio),
--- a/mm/huge_memory.c~mm-fs-remove-filemap_nr_thps-functions-and-their-users
+++ a/mm/huge_memory.c
@@ -3937,7 +3937,6 @@ static int __folio_freeze_and_split_unma
} else {
lruvec_stat_mod_folio(folio,
NR_FILE_THPS, -nr);
- filemap_nr_thps_dec(mapping);
}
}
}
--- a/mm/khugepaged.c~mm-fs-remove-filemap_nr_thps-functions-and-their-users
+++ a/mm/khugepaged.c
@@ -2469,21 +2469,6 @@ out_unlock:
goto xa_unlocked;
}
- if (!is_shmem) {
- filemap_nr_thps_inc(mapping);
- /*
- * Paired with the fence in do_dentry_open() -> get_write_access()
- * to ensure i_writecount is up to date and the update to nr_thps
- * is visible. Ensures the page cache will be truncated if the
- * file is opened writable.
- */
- smp_mb();
- if (inode_is_open_for_write(mapping->host)) {
- result = SCAN_FAIL;
- filemap_nr_thps_dec(mapping);
- }
- }
-
xa_locked:
xas_unlock_irq(&xas);
xa_unlocked:
@@ -2661,19 +2646,6 @@ rollback:
folio_putback_lru(folio);
folio_put(folio);
}
- /*
- * Undo the updates of filemap_nr_thps_inc for non-SHMEM
- * file only. This undo is not needed unless failure is
- * due to SCAN_COPY_MC.
- */
- if (!is_shmem && result == SCAN_COPY_MC) {
- filemap_nr_thps_dec(mapping);
- /*
- * Paired with the fence in do_dentry_open() -> get_write_access()
- * to ensure the update to nr_thps is visible.
- */
- smp_mb();
- }
new_folio->mapping = NULL;
_
Patches currently in -mm which might be from ziy@nvidia.com are
mm-khugepaged-remove-read_only_thp_for_fs-check.patch
mm-khugepaged-add-folio-dirty-check-after-try_to_unmap.patch
mm-huge_memory-remove-read_only_thp_for_fs-from-file_thp_enabled.patch
mm-khugepaged-remove-read_only_thp_for_fs-check-in-hugepage_enabled.patch
mm-remove-read_only_thp_for_fs-kconfig-option.patch
mm-fs-remove-filemap_nr_thps-functions-and-their-users.patch
fs-remove-nr_thps-from-struct-address_space.patch
mm-huge_memory-remove-folio-split-check-for-read_only_thp_for_fs.patch
mm-truncate-use-folio_split-in-truncate_inode_partial_folio.patch
fs-btrfs-remove-a-comment-referring-to-read_only_thp_for_fs.patch
selftests-mm-remove-read_only_thp_for_fs-in-khugepaged.patch
selftests-mm-remove-read_only_thp_for_fs-code-from-guard-regions.patch
^ permalink raw reply [flat|nested] 2+ messages in thread
* + mm-fs-remove-filemap_nr_thps-functions-and-their-users.patch added to mm-new branch
@ 2026-04-29 16:13 Andrew Morton
0 siblings, 0 replies; 2+ messages in thread
From: Andrew Morton @ 2026-04-29 16:13 UTC (permalink / raw)
To: mm-commits, ziy, akpm
The patch titled
Subject: mm: fs: remove filemap_nr_thps*() functions and their users
has been added to the -mm mm-new branch. Its filename is
mm-fs-remove-filemap_nr_thps-functions-and-their-users.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-fs-remove-filemap_nr_thps-functions-and-their-users.patch
This patch will later appear in the mm-new branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews. Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.
The mm-new branch of mm.git is not included in linux-next
If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via various
branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there most days
------------------------------------------------------
From: Zi Yan <ziy@nvidia.com>
Subject: mm: fs: remove filemap_nr_thps*() functions and their users
Date: Wed, 29 Apr 2026 11:35:29 -0400
They are used by READ_ONLY_THP_FOR_FS to handle writes to FSes without
large folio support, so that read-only THPs created in these FSes are not
seen by the FSes when the underlying fd becomes writable. Now read-only
PMD THPs only appear in a FS with large folio support and the supported
orders include PMD_ORDER.
READ_ONLY_THP_FOR_FS was using mapping->nr_thps, inode->i_writecount, and
smp_mb() to prevent writes to a read-only THP and collapsing writable
folios into a THP. In collapse_file(), mapping->nr_thps is increased,
then smp_mb(), and if inode->i_writecount > 0, collapse is stopped, while
do_dentry_open() first increases inode->i_writecount, then a full memory
fence, and if mapping->nr_thps > 0, all read-only THPs are truncated.
Now this mechanism can be removed along with READ_ONLY_THP_FOR_FS code,
since a dirty folio check has been added after try_to_unmap() in
collapse_file() to prevent dirty folios from being collapsed as clean.
Link: https://lore.kernel.org/20260429153538.727855-2-ziy@nvidia.com
Signed-off-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.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: Lance Yang <lance.yang@linux.dev>
Cc: Liam Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nico Pache <npache@redhat.com>
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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
fs/open.c | 27 ---------------------------
include/linux/pagemap.h | 29 -----------------------------
mm/filemap.c | 1 -
mm/huge_memory.c | 1 -
mm/khugepaged.c | 28 ----------------------------
5 files changed, 86 deletions(-)
--- a/fs/open.c~mm-fs-remove-filemap_nr_thps-functions-and-their-users
+++ a/fs/open.c
@@ -968,33 +968,6 @@ static int do_dentry_open(struct file *f
if ((f->f_flags & O_DIRECT) && !(f->f_mode & FMODE_CAN_ODIRECT))
return -EINVAL;
- /*
- * XXX: Huge page cache doesn't support writing yet. Drop all page
- * cache for this file before processing writes.
- */
- if (f->f_mode & FMODE_WRITE) {
- /*
- * Depends on full fence from get_write_access() to synchronize
- * against collapse_file() regarding i_writecount and nr_thps
- * updates. Ensures subsequent insertion of THPs into the page
- * cache will fail.
- */
- if (filemap_nr_thps(inode->i_mapping)) {
- struct address_space *mapping = inode->i_mapping;
-
- filemap_invalidate_lock(inode->i_mapping);
- /*
- * unmap_mapping_range just need to be called once
- * here, because the private pages is not need to be
- * unmapped mapping (e.g. data segment of dynamic
- * shared libraries here).
- */
- unmap_mapping_range(mapping, 0, 0, 0);
- truncate_inode_pages(mapping, 0);
- filemap_invalidate_unlock(inode->i_mapping);
- }
- }
-
return 0;
cleanup_all:
--- a/include/linux/pagemap.h~mm-fs-remove-filemap_nr_thps-functions-and-their-users
+++ a/include/linux/pagemap.h
@@ -545,35 +545,6 @@ static inline size_t mapping_max_folio_s
return PAGE_SIZE << mapping_max_folio_order(mapping);
}
-static inline int filemap_nr_thps(const struct address_space *mapping)
-{
-#ifdef CONFIG_READ_ONLY_THP_FOR_FS
- return atomic_read(&mapping->nr_thps);
-#else
- return 0;
-#endif
-}
-
-static inline void filemap_nr_thps_inc(struct address_space *mapping)
-{
-#ifdef CONFIG_READ_ONLY_THP_FOR_FS
- if (!mapping_large_folio_support(mapping))
- atomic_inc(&mapping->nr_thps);
-#else
- WARN_ON_ONCE(mapping_large_folio_support(mapping) == 0);
-#endif
-}
-
-static inline void filemap_nr_thps_dec(struct address_space *mapping)
-{
-#ifdef CONFIG_READ_ONLY_THP_FOR_FS
- if (!mapping_large_folio_support(mapping))
- atomic_dec(&mapping->nr_thps);
-#else
- WARN_ON_ONCE(mapping_large_folio_support(mapping) == 0);
-#endif
-}
-
struct address_space *folio_mapping(const struct folio *folio);
/**
--- a/mm/filemap.c~mm-fs-remove-filemap_nr_thps-functions-and-their-users
+++ a/mm/filemap.c
@@ -189,7 +189,6 @@ static void filemap_unaccount_folio(stru
lruvec_stat_mod_folio(folio, NR_SHMEM_THPS, -nr);
} else if (folio_test_pmd_mappable(folio)) {
lruvec_stat_mod_folio(folio, NR_FILE_THPS, -nr);
- filemap_nr_thps_dec(mapping);
}
if (test_bit(AS_KERNEL_FILE, &folio->mapping->flags))
mod_node_page_state(folio_pgdat(folio),
--- a/mm/huge_memory.c~mm-fs-remove-filemap_nr_thps-functions-and-their-users
+++ a/mm/huge_memory.c
@@ -3951,7 +3951,6 @@ static int __folio_freeze_and_split_unma
} else {
lruvec_stat_mod_folio(folio,
NR_FILE_THPS, -nr);
- filemap_nr_thps_dec(mapping);
}
}
}
--- a/mm/khugepaged.c~mm-fs-remove-filemap_nr_thps-functions-and-their-users
+++ a/mm/khugepaged.c
@@ -2469,21 +2469,6 @@ out_unlock:
goto xa_unlocked;
}
- if (!is_shmem) {
- filemap_nr_thps_inc(mapping);
- /*
- * Paired with the fence in do_dentry_open() -> get_write_access()
- * to ensure i_writecount is up to date and the update to nr_thps
- * is visible. Ensures the page cache will be truncated if the
- * file is opened writable.
- */
- smp_mb();
- if (inode_is_open_for_write(mapping->host)) {
- result = SCAN_FAIL;
- filemap_nr_thps_dec(mapping);
- }
- }
-
xa_locked:
xas_unlock_irq(&xas);
xa_unlocked:
@@ -2661,19 +2646,6 @@ rollback:
folio_putback_lru(folio);
folio_put(folio);
}
- /*
- * Undo the updates of filemap_nr_thps_inc for non-SHMEM
- * file only. This undo is not needed unless failure is
- * due to SCAN_COPY_MC.
- */
- if (!is_shmem && result == SCAN_COPY_MC) {
- filemap_nr_thps_dec(mapping);
- /*
- * Paired with the fence in do_dentry_open() -> get_write_access()
- * to ensure the update to nr_thps is visible.
- */
- smp_mb();
- }
new_folio->mapping = NULL;
_
Patches currently in -mm which might be from ziy@nvidia.com are
mm-khugepaged-remove-read_only_thp_for_fs-check.patch
mm-khugepaged-add-folio-dirty-check-after-try_to_unmap.patch
mm-huge_memory-remove-read_only_thp_for_fs-from-file_thp_enabled.patch
mm-khugepaged-remove-read_only_thp_for_fs-check-in-hugepage_enabled.patch
mm-remove-read_only_thp_for_fs-kconfig-option.patch
mm-fs-remove-filemap_nr_thps-functions-and-their-users.patch
fs-remove-nr_thps-from-struct-address_space.patch
mm-huge_memory-remove-folio-split-check-for-read_only_thp_for_fs.patch
mm-truncate-use-folio_split-in-truncate_inode_partial_folio.patch
fs-btrfs-remove-a-comment-referring-to-read_only_thp_for_fs.patch
selftests-mm-remove-read_only_thp_for_fs-in-khugepaged.patch
selftests-mm-remove-read_only_thp_for_fs-code-from-guard-regions.patch
mm-khugepaged-enable-clean-pagecache-folio-collapse-for-writable-files.patch
selftests-mm-add-writable-file-collapse-tests-for-khugepaged.patch
^ permalink raw reply [flat|nested] 2+ messages in thread
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