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Commit ca49ca71 authored by Mike Rapoport's avatar Mike Rapoport Committed by Linus Torvalds
Browse files

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

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: default avatarMike Rapoport <rppt@linux.vnet.ibm.com>
Acked-by: default avatarHillf 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 897ab3e0

fs/userfaultfd.c

+28 −0
Original line number Diff line number Diff line
@@ -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;

include/linux/userfaultfd_k.h

+7 −0
Original line number Diff line number Diff line
@@ -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 */

include/uapi/linux/userfaultfd.h

+4 −1
Original line number Diff line number Diff line
@@ -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;

kernel/exit.c

+2 −0
Original line number Diff line number Diff line
@@ -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();