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/[email protected]/).

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/[email protected]/
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/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Yang Shi <[email protected]>
Reviewed-by: Miaohe Lin <[email protected]>
Acked-by: Song Liu <[email protected]>
Acked-by: Vlastmil Babka <[email protected]>
Cc: Kirill A. Shutemov <[email protected]>
Cc: Matthew Wilcox (Oracle) <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Song Liu <[email protected]>
Cc: Theodore Ts'o <[email protected]>
Cc: Zi Yan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions