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userfaultfd: provide pid in userfault msg 

It could be useful for calculating downtime during postcopy live
migration per vCPU.  Side observer or application itself will be
informed about proper task's sleep during userfaultfd processing.

Process's thread id is being provided when user requeste it by setting
UFFD_FEATURE_THREAD_ID bit into uffdio_api.features.

Link: http://lkml.kernel.org/r/20170802165145.22628-6-aarcange@redhat.com
Signed-off-by: Alexey Perevalov <a.perevalov@samsung.com>
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Maxime Coquelin <maxime.coquelin@redhat.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Alexey Perevalov 2017-09-06 16:23:56 -07:00 committed by Linus Torvalds
parent 2376dd7ced
commit 9d4ac93482
2 changed files with 13 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
fs/userfaultfd.c
View File

@ -178,7 +178,8 @@ static inline void msg_init(struct uffd_msg *msg)
static inline struct uffd_msg userfault_msg(unsigned long address,
unsigned int flags,
unsigned long reason)
unsigned long reason,
unsigned int features)
{
struct uffd_msg msg;
msg_init(&msg);
@ -202,6 +203,8 @@ static inline struct uffd_msg userfault_msg(unsigned long address,
* write protect fault.
*/
msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_WP;
if (features & UFFD_FEATURE_THREAD_ID)
msg.arg.pagefault.ptid = task_pid_vnr(current);
return msg;
}
@ -422,7 +425,8 @@ int handle_userfault(struct vm_fault *vmf, unsigned long reason)
init_waitqueue_func_entry(&uwq.wq, userfaultfd_wake_function);
uwq.wq.private = current;
uwq.msg = userfault_msg(vmf->address, vmf->flags, reason);
uwq.msg = userfault_msg(vmf->address, vmf->flags, reason,
ctx->features);
uwq.ctx = ctx;
uwq.waken = false;

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

@ -24,7 +24,8 @@
UFFD_FEATURE_EVENT_UNMAP | \
UFFD_FEATURE_MISSING_HUGETLBFS | \
UFFD_FEATURE_MISSING_SHMEM | \
UFFD_FEATURE_SIGBUS)
UFFD_FEATURE_SIGBUS | \
UFFD_FEATURE_THREAD_ID)
#define UFFD_API_IOCTLS \
((__u64)1 << _UFFDIO_REGISTER | \
(__u64)1 << _UFFDIO_UNREGISTER | \
@ -79,6 +80,7 @@ struct uffd_msg {
struct {
__u64 flags;
__u64 address;
__u32 ptid;
} pagefault;
struct {
@ -158,8 +160,9 @@ struct uffdio_api {
* UFFD_FEATURE_SIGBUS feature means no page-fault
* (UFFD_EVENT_PAGEFAULT) event will be delivered, instead
* a SIGBUS signal will be sent to the faulting process.
* The application process can enable this behavior by adding
* it to uffdio_api.features.
*
* UFFD_FEATURE_THREAD_ID pid of the page faulted task_struct will
* be returned, if feature is not requested 0 will be returned.
*/
#define UFFD_FEATURE_PAGEFAULT_FLAG_WP (1<<0)
#define UFFD_FEATURE_EVENT_FORK (1<<1)
@ -169,6 +172,7 @@ struct uffdio_api {
#define UFFD_FEATURE_MISSING_SHMEM (1<<5)
#define UFFD_FEATURE_EVENT_UNMAP (1<<6)
#define UFFD_FEATURE_SIGBUS (1<<7)
#define UFFD_FEATURE_THREAD_ID (1<<8)
__u64 features;
__u64 ioctls;