The patch titled
Subject: mremap: check if it's possible to split original vma
has been removed from the -mm tree. Its filename was
mremap-check-if-its-possible-to-split-original-vma.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: Dmitry Safonov <dima@xxxxxxxxxx>
Subject: mremap: check if it's possible to split original vma
If original VMA can't be split at the desired address, do_munmap() will
fail and leave both new-copied VMA and old VMA. De-facto it's
MREMAP_DONTUNMAP behaviour, which is unexpected.
Currently, it may fail such way for hugetlbfs and dax device mappings.
Minimize such unpleasant situations to OOM by checking .may_split() before
attempting to create a VMA copy.
Link: https://lkml.kernel.org/r/20201013013416.390574-6-dima@xxxxxxxxxx
Signed-off-by: Dmitry Safonov <dima@xxxxxxxxxx>
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Brian Geffon <bgeffon@xxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Dave Jiang <dave.jiang@xxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Ralph Campbell <rcampbell@xxxxxxxxxx>
Cc: Russell King <linux@xxxxxxxxxxxxxxx>
Cc: Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Vishal Verma <vishal.l.verma@xxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/mremap.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
--- a/mm/mremap.c~mremap-check-if-its-possible-to-split-original-vma
+++ a/mm/mremap.c
@@ -493,7 +493,7 @@ static unsigned long move_vma(struct vm_
unsigned long excess = 0;
unsigned long hiwater_vm;
int split = 0;
- int err;
+ int err = 0;
bool need_rmap_locks;
/*
@@ -503,6 +503,15 @@ static unsigned long move_vma(struct vm_
if (mm->map_count >= sysctl_max_map_count - 3)
return -ENOMEM;
+ if (vma->vm_ops && vma->vm_ops->may_split) {
+ if (vma->vm_start != old_addr)
+ err = vma->vm_ops->may_split(vma, old_addr);
+ if (!err && vma->vm_end != old_addr + old_len)
+ err = vma->vm_ops->may_split(vma, old_addr + old_len);
+ if (err)
+ return err;
+ }
+
/*
* Advise KSM to break any KSM pages in the area to be moved:
* it would be confusing if they were to turn up at the new
_
Patches currently in -mm which might be from dima@xxxxxxxxxx are
