[patch 114/163] mm/mremap: it is sure to have enough space when extent meets requirement

Andrew Morton
2020-08-07T06:23:44Z

From: Wei Yang <richard.weiyang@linux.alibaba.com>
Subject: mm/mremap: it is sure to have enough space when extent meets requirement

Patch series "mm/mremap: cleanup move_page_tables() a little", v5.

move_page_tables() tries to move page table by PMD or PTE.

The root reason is if it tries to move PMD, both old and new range should
be PMD aligned. But current code calculate old range and new range
separately. This leads to some redundant check and calculation.

This cleanup tries to consolidate the range check in one place to reduce
some extra range handling.

This patch (of 3):

old_end is passed to these two functions to check whether there is enough
space to do the move, while this check is done before invoking these
functions.

These two functions only would be invoked when extent meets the
requirement and there is one check before invoking these functions:

if (extent > old_end - old_addr)
extent = old_end - old_addr;

This implies (old_end - old_addr) won't fail the check in these two
functions.

Link: http://lkml.kernel.org/r/20200710092835.56368-1-richard.weiyang@linux.alibaba.com
Link: http://lkml.kernel.org/r/20200710092835.56368-2-richard.weiyang@linux.alibaba.com
Link: http://lkml.kernel.org/r/20200708095028.41706-1-richard.weiyang@linux.alibaba.com
Link: http://lkml.kernel.org/r/20200708095028.41706-2-richard.weiyang@linux.alibaba.com
Signed-off-by: Wei Yang <richard.weiyang@linux.alibaba.com>
Tested-by: Dmitry Osipenko <digetx@gmail.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yang Shi <yang.shi@linux.alibaba.com>
Cc: Thomas Hellstrom (VMware) <thomas_os@shipmail.org>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Thomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

include/linux/huge_mm.h | 2 +-
mm/huge_memory.c | 7 ++-----
mm/mremap.c | 10 ++++------
3 files changed, 7 insertions(+), 12 deletions(-)

--- a/include/linux/huge_mm.h~mm-mremap-it-is-sure-to-have-enough-space-when-extent-meets-requirement
+++ a/include/linux/huge_mm.h
@@ -42,7 +42,7 @@ extern int mincore_huge_pmd(struct vm_ar
unsigned long addr, unsigned long end,
unsigned char *vec);
extern bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
- unsigned long new_addr, unsigned long old_end,
+ unsigned long new_addr,
pmd_t *old_pmd, pmd_t *new_pmd);
extern int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
unsigned long addr, pgprot_t newprot,
--- a/mm/huge_memory.c~mm-mremap-it-is-sure-to-have-enough-space-when-extent-meets-requirement
+++ a/mm/huge_memory.c
@@ -1722,17 +1722,14 @@ static pmd_t move_soft_dirty_pmd(pmd_t p
}

bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
- unsigned long new_addr, unsigned long old_end,
- pmd_t *old_pmd, pmd_t *new_pmd)
+ unsigned long new_addr, pmd_t *old_pmd, pmd_t *new_pmd)
{
spinlock_t *old_ptl, *new_ptl;
pmd_t pmd;
struct mm_struct *mm = vma->vm_mm;
bool force_flush = false;

- if ((old_addr & ~HPAGE_PMD_MASK) ||
- (new_addr & ~HPAGE_PMD_MASK) ||
- old_end - old_addr < HPAGE_PMD_SIZE)
+ if ((old_addr & ~HPAGE_PMD_MASK) || (new_addr & ~HPAGE_PMD_MASK))
return false;

/*
--- a/mm/mremap.c~mm-mremap-it-is-sure-to-have-enough-space-when-extent-meets-requirement
+++ a/mm/mremap.c
@@ -193,15 +193,13 @@ static void move_ptes(struct vm_area_str

#ifdef CONFIG_HAVE_MOVE_PMD
static bool move_normal_pmd(struct vm_area_struct *vma, unsigned long old_addr,
- unsigned long new_addr, unsigned long old_end,
- pmd_t *old_pmd, pmd_t *new_pmd)
+ unsigned long new_addr, pmd_t *old_pmd, pmd_t *new_pmd)
{
spinlock_t *old_ptl, *new_ptl;
struct mm_struct *mm = vma->vm_mm;
pmd_t pmd;

- if ((old_addr & ~PMD_MASK) || (new_addr & ~PMD_MASK)
- || old_end - old_addr < PMD_SIZE)
+ if ((old_addr & ~PMD_MASK) || (new_addr & ~PMD_MASK))
return false;

/*
@@ -292,7 +290,7 @@ unsigned long move_page_tables(struct vm
if (need_rmap_locks)
take_rmap_locks(vma);
moved = move_huge_pmd(vma, old_addr, new_addr,
- old_end, old_pmd, new_pmd);
+ old_pmd, new_pmd);
if (need_rmap_locks)
drop_rmap_locks(vma);
if (moved)
@@ -312,7 +310,7 @@ unsigned long move_page_tables(struct vm
if (need_rmap_locks)
take_rmap_locks(vma);
moved = move_normal_pmd(vma, old_addr, new_addr,
- old_end, old_pmd, new_pmd);
+ old_pmd, new_pmd);
if (need_rmap_locks)
drop_rmap_locks(vma);
if (moved)
_