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userfaultfd: non-cooperative: add mremap() event

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The event denotes that an area [start:end] moves to different location.
Length change isn't reported as "new" addresses, if they appear on the
uffd reader side they will not contain any data and the latter can just
zeromap them.

Waiting for the event ACK is also done outside of mmap sem, as for fork
event.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Pavel Emelyanov <[email protected]>
Signed-off-by: Mike Rapoport <[email protected]>
Signed-off-by: Andrea Arcangeli <[email protected]>
Cc: "Dr. David Alan Gilbert" <[email protected]>
Cc: Hillf Danton <[email protected]>
Cc: Michael Rapoport <[email protected]>
Cc: Mike Kravetz <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Pavel Emelyanov 2017-02-22 15:42:34 -08:00 • committed by Linus Torvalds
commit 72f87654c6
4 changed files with 76 additions and 6 deletions
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37
fs/userfaultfd.c
View file

@ -596,6 +596,43 @@ void dup_userfaultfd_complete(struct list_head *fcs)
}
}
void mremap_userfaultfd_prep(struct vm_area_struct *vma,
struct vm_userfaultfd_ctx *vm_ctx)
{
struct userfaultfd_ctx *ctx;
ctx = vma->vm_userfaultfd_ctx.ctx;
if (ctx && (ctx->features & UFFD_FEATURE_EVENT_REMAP)) {
vm_ctx->ctx = ctx;
userfaultfd_ctx_get(ctx);
}
}
void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx vm_ctx,
unsigned long from, unsigned long to,
unsigned long len)
{
struct userfaultfd_ctx *ctx = vm_ctx.ctx;
struct userfaultfd_wait_queue ewq;
if (!ctx)
return;
if (to & ~PAGE_MASK) {
userfaultfd_ctx_put(ctx);
return;
}
msg_init(&ewq.msg);
ewq.msg.event = UFFD_EVENT_REMAP;
ewq.msg.arg.remap.from = from;
ewq.msg.arg.remap.to = to;
ewq.msg.arg.remap.len = len;
userfaultfd_event_wait_completion(ctx, &ewq);
}
static int userfaultfd_release(struct inode *inode, struct file *file)
{
struct userfaultfd_ctx *ctx = file->private_data;