From: Alexey Perevalov <a.perevalov@xxxxxxxxxxx> Subject: 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@xxxxxxxxxx Signed-off-by: Alexey Perevalov <a.perevalov@xxxxxxxxxxx> Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx> Cc: "Dr. David Alan Gilbert" <dgilbert@xxxxxxxxxx> Cc: Maxime Coquelin <maxime.coquelin@xxxxxxxxxx> Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx> Cc: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/userfaultfd.c | 8 ++++++-- include/uapi/linux/userfaultfd.h | 10 +++++++--- 2 files changed, 13 insertions(+), 5 deletions(-) diff -puN fs/userfaultfd.c~userfaultfd-provide-pid-in-userfault-msg fs/userfaultfd.c --- a/fs/userfaultfd.c~userfaultfd-provide-pid-in-userfault-msg +++ a/fs/userfaultfd.c @@ -178,7 +178,8 @@ static inline void msg_init(struct uffd_ 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_ * 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 *vm 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; diff -puN include/uapi/linux/userfaultfd.h~userfaultfd-provide-pid-in-userfault-msg include/uapi/linux/userfaultfd.h --- a/include/uapi/linux/userfaultfd.h~userfaultfd-provide-pid-in-userfault-msg +++ a/include/uapi/linux/userfaultfd.h @@ -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; _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
