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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: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Andrea 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Pavel Emelyanov 2017-02-22 15:42:40 -08:00 committed by Linus Torvalds
parent 90794bf19d
commit 05ce77249d
4 changed files with 51 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

28
fs/userfaultfd.c
View File

@ -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;

12
include/linux/userfaultfd_k.h
View File

@ -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 */

10
include/uapi/linux/userfaultfd.h
View File

@ -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;

2
mm/madvise.c
View File

@ -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;
}