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userfaultfd: non-cooperative: add event for exit() notification

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Allow userfaultfd monitor track termination of the processes that have
memory backed by the uffd.

[rppt@linux.vnet.ibm.com: add comment]
  Link: http://lkml.kernel.org/r/20170202135448.GB19804@rapoport-lnxLink: http://lkml.kernel.org/r/1485542673-24387-4-git-send-email-rppt@linux.vnet.ibm.com
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Mike Rapoport 2017-02-24 14:58:25 -08:00 committed by Linus Torvalds
parent 897ab3e0c4
commit ca49ca7114
4 changed files with 41 additions and 1 deletions
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28
fs/userfaultfd.c
View File

@ -774,6 +774,34 @@ void userfaultfd_unmap_complete(struct mm_struct *mm, struct list_head *uf)
}
}
void userfaultfd_exit(struct mm_struct *mm)
{
struct vm_area_struct *vma = mm->mmap;
/*
* We can do the vma walk without locking because the caller
* (exit_mm) knows it now has exclusive access
*/
while (vma) {
struct userfaultfd_ctx *ctx = vma->vm_userfaultfd_ctx.ctx;
if (ctx && (ctx->features & UFFD_FEATURE_EVENT_EXIT)) {
struct userfaultfd_wait_queue ewq;
userfaultfd_ctx_get(ctx);
msg_init(&ewq.msg);
ewq.msg.event = UFFD_EVENT_EXIT;
userfaultfd_event_wait_completion(ctx, &ewq);
ctx->features &= ~UFFD_FEATURE_EVENT_EXIT;
}
vma = vma->vm_next;
}
}
static int userfaultfd_release(struct inode *inode, struct file *file)
{
struct userfaultfd_ctx *ctx = file->private_data;

7
include/linux/userfaultfd_k.h
View File

@ -72,6 +72,8 @@ extern int userfaultfd_unmap_prep(struct vm_area_struct *vma,
extern void userfaultfd_unmap_complete(struct mm_struct *mm,
struct list_head *uf);
extern void userfaultfd_exit(struct mm_struct *mm);
#else /* CONFIG_USERFAULTFD */
/* mm helpers */
@ -136,6 +138,11 @@ static inline void userfaultfd_unmap_complete(struct mm_struct *mm,
struct list_head *uf)
{
}
static inline void userfaultfd_exit(struct mm_struct *mm)
{
}
#endif /* CONFIG_USERFAULTFD */
#endif /* _LINUX_USERFAULTFD_K_H */

5
include/uapi/linux/userfaultfd.h
View File

@ -18,7 +18,8 @@
* means the userland is reading).
*/
#define UFFD_API ((__u64)0xAA)
#define UFFD_API_FEATURES (UFFD_FEATURE_EVENT_FORK | \
#define UFFD_API_FEATURES (UFFD_FEATURE_EVENT_EXIT | \
UFFD_FEATURE_EVENT_FORK | \
UFFD_FEATURE_EVENT_REMAP | \
UFFD_FEATURE_EVENT_REMOVE | \
UFFD_FEATURE_EVENT_UNMAP | \
@ -112,6 +113,7 @@ struct uffd_msg {
#define UFFD_EVENT_REMAP 0x14
#define UFFD_EVENT_REMOVE 0x15
#define UFFD_EVENT_UNMAP 0x16
#define UFFD_EVENT_EXIT 0x17
/* flags for UFFD_EVENT_PAGEFAULT */
#define UFFD_PAGEFAULT_FLAG_WRITE (1<<0) /* If this was a write fault */
@ -161,6 +163,7 @@ struct uffdio_api {
#define UFFD_FEATURE_MISSING_HUGETLBFS (1<<4)
#define UFFD_FEATURE_MISSING_SHMEM (1<<5)
#define UFFD_FEATURE_EVENT_UNMAP (1<<6)
#define UFFD_FEATURE_EVENT_EXIT (1<<7)
__u64 features;
__u64 ioctls;

2
kernel/exit.c
View File

@ -45,6 +45,7 @@
#include <linux/task_io_accounting_ops.h>
#include <linux/tracehook.h>
#include <linux/fs_struct.h>
#include <linux/userfaultfd_k.h>
#include <linux/init_task.h>
#include <linux/perf_event.h>
#include <trace/events/sched.h>
@ -547,6 +548,7 @@ static void exit_mm(void)
enter_lazy_tlb(mm, current);
task_unlock(current);
mm_update_next_owner(mm);
userfaultfd_exit(mm);
mmput(mm);
if (test_thread_flag(TIF_MEMDIE))
exit_oom_victim();