On Fri 27-01-17 20:44:30, Mike Rapoport wrote:
> When a non-cooperative userfaultfd monitor copies pages in the background,
> it may encounter regions that were already unmapped. Addition of
> UFFD_EVENT_UNMAP allows the uffd monitor to track precisely changes in the
> virtual memory layout.
>
> Since there might be different uffd contexts for the affected VMAs, we
> first should create a temporary representation for the unmap event for each
> uffd context and then notify them one by one to the appropriate userfault
> file descriptors.
>
> The event notification occurs after the mmap_sem has been released.
>
> Signed-off-by: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx>
> Acked-by: Hillf Danton <hillf.zj@xxxxxxxxxxxxxxx>
This breaks NOMMU compilation
---
>From 510948533b059f4f5033464f9f4a0c32d4ab0c08 Mon Sep 17 00:00:00 2001
From: Michal Hocko <mhocko@xxxxxxxx>
Date: Thu, 2 Feb 2017 10:08:47 +0100
Subject: [PATCH] mmotm:
userfaultfd-non-cooperative-add-event-for-memory-unmaps-fix
This breaks compilation on nommu configs.
mm/nommu.c:1201:15: error: conflicting types for 'do_mmap'
unsigned long do_mmap(struct file *file,
^
In file included from mm/nommu.c:19:0:
./include/linux/mm.h:2089:22: note: previous declaration of 'do_mmap' was here
extern unsigned long do_mmap(struct file *file, unsigned long addr,
^
mm/nommu.c:1580:5: error: conflicting types for 'do_munmap'
int do_munmap(struct mm_struct *mm, unsigned long start, size_t len)
^
In file included from mm/nommu.c:19:0:
./include/linux/mm.h:2093:12: note: previous declaration of 'do_munmap' was here
extern int do_munmap(struct mm_struct *, unsigned long, size_t,
^
make[1]: *** [mm/nommu.o] Error 1
CONFIG_USERFAULTFD depends on CONFIG_MMU so I guess we are OK to just ignore the
argument.
Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
---
mm/nommu.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/mm/nommu.c b/mm/nommu.c
index d35088a4b73d..f78d06459ba4 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -1205,7 +1205,8 @@ unsigned long do_mmap(struct file *file,
unsigned long flags,
vm_flags_t vm_flags,
unsigned long pgoff,
- unsigned long *populate)
+ unsigned long *populate,
+ struct list_head *uf_unused)
{
struct vm_area_struct *vma;
struct vm_region *region;
@@ -1577,7 +1578,7 @@ static int shrink_vma(struct mm_struct *mm,
* - under NOMMU conditions the chunk to be unmapped must be backed by a single
* VMA, though it need not cover the whole VMA
*/
-int do_munmap(struct mm_struct *mm, unsigned long start, size_t len)
+int do_munmap(struct mm_struct *mm, unsigned long start, size_t len, struct list_head *uf)
{
struct vm_area_struct *vma;
unsigned long end;
@@ -1643,7 +1644,7 @@ int vm_munmap(unsigned long addr, size_t len)
int ret;
down_write(&mm->mmap_sem);
- ret = do_munmap(mm, addr, len);
+ ret = do_munmap(mm, addr, len, NULL);
up_write(&mm->mmap_sem);
return ret;
}
--
2.11.0
--
Michal Hocko
SUSE Labs
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