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userfaultfd: provide pid in userfault msg

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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/[email protected]
Signed-off-by: Alexey Perevalov <[email protected]>
Signed-off-by: Andrea Arcangeli <[email protected]>
Cc: "Dr. David Alan Gilbert" <[email protected]>
Cc: Maxime Coquelin <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Mike Rapoport <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Alexey Perevalov 2017-09-06 16:23:56 -07:00 • committed by Linus Torvalds
commit 9d4ac93482
2 changed files with 13 additions and 5 deletions
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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;