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Date: Wed, 13 May 2015 17:53:41 +0300
From: Pavel Emelyanov <xemul@...allels.com>
To: Andrea Arcangeli <aarcange@...hat.com>
CC: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Linux MM <linux-mm@...ck.org>,
Sanidhya Kashyap <sanidhya.gatech@...il.com>
Subject: [PATCH 5/5] uffd: 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.
Signed-off-by: Pavel Emelyanov <xemul@...allels.com>
---
fs/userfaultfd.c | 26 ++++++++++++++++++++++++++
include/linux/userfaultfd_k.h | 10 ++++++++++
include/uapi/linux/userfaultfd.h | 9 ++++++++-
mm/madvise.c | 2 ++
4 files changed, 46 insertions(+), 1 deletion(-)
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 697e636..6e80a02 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -546,6 +546,32 @@ void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx vm_ctx, unsigned long
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 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);
+ *prev = NULL; /* We wait for ACK w/o the mmap semaphore */
+ up_read(&vma->vm_mm->mmap_sem);
+
+ 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(&vma->vm_mm->mmap_sem);
+}
+
static int userfaultfd_release(struct inode *inode, struct file *file)
{
struct userfaultfd_ctx *ctx = file->private_data;
diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h
index 0ed5dce..2f72069 100644
--- a/include/linux/userfaultfd_k.h
+++ b/include/linux/userfaultfd_k.h
@@ -82,6 +82,10 @@ extern void mremap_userfaultfd_prep(struct vm_area_struct *, struct vm_userfault
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 */
@@ -131,6 +135,12 @@ static inline void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx ctx,
unsigned long from, unsigned long to, 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 */
diff --git a/include/uapi/linux/userfaultfd.h b/include/uapi/linux/userfaultfd.h
index 59a141c..d0d1ef1 100644
--- a/include/uapi/linux/userfaultfd.h
+++ b/include/uapi/linux/userfaultfd.h
@@ -14,7 +14,7 @@
* After implementing the respective features it will become:
* #define UFFD_API_FEATURES (UFFD_FEATURE_PAGEFAULT_FLAG_WP)
*/
-#define UFFD_API_FEATURES (UFFD_FEATURE_EVENT_FORK|UFFD_FEATURE_EVENT_REMAP)
+#define UFFD_API_FEATURES (UFFD_FEATURE_EVENT_FORK|UFFD_FEATURE_EVENT_REMAP|UFFD_FEATURE_EVENT_MADVDONTNEED)
#define UFFD_API_IOCTLS \
((__u64)1 << _UFFDIO_REGISTER | \
(__u64)1 << _UFFDIO_UNREGISTER | \
@@ -79,6 +79,11 @@ struct uffd_msg {
} remap;
struct {
+ __u64 start;
+ __u64 end;
+ } madv_dn;
+
+ struct {
/* unused reserved fields */
__u64 reserved1;
__u64 reserved2;
@@ -93,6 +98,7 @@ 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 */
@@ -116,6 +122,7 @@ struct uffdio_api {
#endif
#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;
diff --git a/mm/madvise.c b/mm/madvise.c
index 10f62b7..3ea20e2 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -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>
@@ -283,6 +284,7 @@ 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;
}
--
1.9.3
--
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