+ sched-coredumph-clarify-the-use-of-mmf_vm_hugepage.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: sched: coredump.h: clarify the use of MMF_VM_HUGEPAGE
has been added to the -mm mm-unstable branch.  Its filename is
     sched-coredumph-clarify-the-use-of-mmf_vm_hugepage.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/sched-coredumph-clarify-the-use-of-mmf_vm_hugepage.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Yang Shi <shy828301@gmail.com>
Subject: sched: coredump.h: clarify the use of MMF_VM_HUGEPAGE

Patch series "Make khugepaged collapse readonly FS THP more consistent", v4.

The readonly FS THP relies on khugepaged to collapse THP for suitable
vmas.  But the behavior is inconsistent for "always" mode
(https://lore.kernel.org/linux-mm/00f195d4-d039-3cf2-d3a1-a2c88de397a0@suse.cz/).

The "always" mode means THP allocation should be tried all the time and
khugepaged should try to collapse THP all the time.  Of course the
allocation and collapse may fail due to other factors and conditions.

Currently file THP may not be collapsed by khugepaged even though all the
conditions are met.  That does break the semantics of "always" mode.

So make sure readonly FS vmas are registered to khugepaged to fix the
break.

Register suitable vmas in common mmap path, that could cover both readonly
FS vmas and shmem vmas, so remove the khugepaged calls in shmem.c.

The patch 1-7 are minor bug fixes, clean up and preparation patches. 
Patch 8 is the real meat.  

Tested with khugepaged test in selftests and the testcase provided by
Vlastimil Babka in
https://lore.kernel.org/lkml/df3b5d1c-a36b-2c73-3e27-99e74983de3a@suse.cz/
by commenting out MADV_HUGEPAGE call.


This patch (of 8):

MMF_VM_HUGEPAGE is set as long as the mm is available for khugepaged by
khugepaged_enter(), not only when VM_HUGEPAGE is set on vma.  Correct the
comment to avoid confusion.

Link: https://lkml.kernel.org/r/20220510203222.24246-1-shy828301@gmail.com
Link: https://lkml.kernel.org/r/20220510203222.24246-2-shy828301@gmail.com
Signed-off-by: Yang Shi <shy828301@gmail.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Acked-by: Song Liu <song@kernel.org>
Acked-by: Vlastmil Babka <vbabka@suse.cz>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Song Liu <songliubraving@fb.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/sched/coredump.h |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/include/linux/sched/coredump.h~sched-coredumph-clarify-the-use-of-mmf_vm_hugepage
+++ a/include/linux/sched/coredump.h
@@ -57,7 +57,8 @@ static inline int get_dumpable(struct mm
 #endif
 					/* leave room for more dump flags */
 #define MMF_VM_MERGEABLE	16	/* KSM may merge identical pages */
-#define MMF_VM_HUGEPAGE		17	/* set when VM_HUGEPAGE is set on vma */
+#define MMF_VM_HUGEPAGE		17	/* set when mm is available for
+					   khugepaged */
 /*
  * This one-shot flag is dropped due to necessity of changing exe once again
  * on NFS restore
_

Patches currently in -mm which might be from shy828301@gmail.com are

sched-coredumph-clarify-the-use-of-mmf_vm_hugepage.patch
mm-khugepaged-remove-redundant-check-for-vm_no_khugepaged.patch
mm-khugepaged-skip-dax-vma.patch
mm-thp-only-regular-file-could-be-thp-eligible.patch
mm-khugepaged-make-khugepaged_enter-void-function.patch
mm-khugepaged-make-hugepage_vma_check-non-static.patch
mm-khugepaged-introduce-khugepaged_enter_vma-helper.patch
mm-mmap-register-suitable-readonly-file-vmas-for-khugepaged.patch