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Commit 05ce7724 authored by Pavel Emelyanov's avatar Pavel Emelyanov Committed by Linus Torvalds
Browse files

userfaultfd: non-cooperative: add madvise() event for MADV_DONTNEED request 

If the page is punched out of the address space the uffd reader should
know this and zeromap the respective area in case of the #PF event.

Link: http://lkml.kernel.org/r/20161216144821.5183-14-aarcange@redhat.com


Signed-off-by: default avatarPavel Emelyanov <xemul@parallels.com>
Signed-off-by: default avatarMike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Michael Rapoport <RAPOPORT@il.ibm.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 90794bf1

fs/userfaultfd.c

+28 −0
Original line number Diff line number Diff line
@@ -633,6 +633,34 @@ void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx *vm_ctx, 
	userfaultfd_event_wait_completion(ctx, &ewq);

}



void madvise_userfault_dontneed(struct vm_area_struct *vma,

				struct vm_area_struct **prev,

				unsigned long start, unsigned long end)

{

	struct mm_struct *mm = vma->vm_mm;

	struct userfaultfd_ctx *ctx;

	struct userfaultfd_wait_queue ewq;



	ctx = vma->vm_userfaultfd_ctx.ctx;

	if (!ctx || !(ctx->features & UFFD_FEATURE_EVENT_MADVDONTNEED))

		return;



	userfaultfd_ctx_get(ctx);

	up_read(&mm->mmap_sem);



	*prev = NULL; /* We wait for ACK w/o the mmap semaphore */



	msg_init(&ewq.msg);



	ewq.msg.event = UFFD_EVENT_MADVDONTNEED;

	ewq.msg.arg.madv_dn.start = start;

	ewq.msg.arg.madv_dn.end = end;



	userfaultfd_event_wait_completion(ctx, &ewq);



	down_read(&mm->mmap_sem);

}



static int userfaultfd_release(struct inode *inode, struct file *file)

{

	struct userfaultfd_ctx *ctx = file->private_data;

include/linux/userfaultfd_k.h

+12 −0
Original line number Diff line number Diff line
@@ -61,6 +61,11 @@ extern void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx *, 
					unsigned long from, unsigned long to,

					unsigned long len);



extern void madvise_userfault_dontneed(struct vm_area_struct *vma,

				       struct vm_area_struct **prev,

				       unsigned long start,

				       unsigned long end);



#else /* CONFIG_USERFAULTFD */



/* mm helpers */
@@ -106,6 +111,13 @@ static inline void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx *ctx, 
					       unsigned long len)

{

}



static inline void madvise_userfault_dontneed(struct vm_area_struct *vma,

					      struct vm_area_struct **prev,

					      unsigned long start,

					      unsigned long end)

{

}

#endif /* CONFIG_USERFAULTFD */



#endif /* _LINUX_USERFAULTFD_K_H */

include/uapi/linux/userfaultfd.h

+9 −1
Original line number Diff line number Diff line
@@ -19,7 +19,8 @@ 
 */

#define UFFD_API ((__u64)0xAA)

#define UFFD_API_FEATURES (UFFD_FEATURE_EVENT_FORK |	    \

			   UFFD_FEATURE_EVENT_REMAP)

			   UFFD_FEATURE_EVENT_REMAP |	    \

			   UFFD_FEATURE_EVENT_MADVDONTNEED)

#define UFFD_API_IOCTLS				\

	((__u64)1 << _UFFDIO_REGISTER |		\

	 (__u64)1 << _UFFDIO_UNREGISTER |	\
@@ -83,6 +84,11 @@ struct uffd_msg { 
			__u64	len;

		} remap;



		struct {

			__u64	start;

			__u64	end;

		} madv_dn;



		struct {

			/* unused reserved fields */

			__u64	reserved1;
@@ -98,6 +104,7 @@ struct uffd_msg { 
#define UFFD_EVENT_PAGEFAULT	0x12

#define UFFD_EVENT_FORK		0x13

#define UFFD_EVENT_REMAP	0x14

#define UFFD_EVENT_MADVDONTNEED	0x15



/* flags for UFFD_EVENT_PAGEFAULT */

#define UFFD_PAGEFAULT_FLAG_WRITE	(1<<0)	/* If this was a write fault */
@@ -119,6 +126,7 @@ struct uffdio_api { 
#define UFFD_FEATURE_PAGEFAULT_FLAG_WP		(1<<0)

#define UFFD_FEATURE_EVENT_FORK			(1<<1)

#define UFFD_FEATURE_EVENT_REMAP		(1<<2)

#define UFFD_FEATURE_EVENT_MADVDONTNEED		(1<<3)

	__u64 features;



	__u64 ioctls;

mm/madvise.c

+2 −0
Original line number Diff line number Diff line
@@ -10,6 +10,7 @@ 
#include <linux/syscalls.h>

#include <linux/mempolicy.h>

#include <linux/page-isolation.h>

#include <linux/userfaultfd_k.h>

#include <linux/hugetlb.h>

#include <linux/falloc.h>

#include <linux/sched.h>
@@ -477,6 +478,7 @@ static long madvise_dontneed(struct vm_area_struct *vma, 
		return -EINVAL;



	zap_page_range(vma, start, end - start, NULL);

	madvise_userfault_dontneed(vma, prev, start, end);

	return 0;

}