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userfaultfd: non-cooperative: add madvise() event for MADV_DONTNEED request

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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.

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 15:42:40 -08:00 • committed by Linus Torvalds
commit 05ce77249d
4 changed files with 51 additions and 1 deletions
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28
fs/userfaultfd.c
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@ -633,6 +633,34 @@ void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx *vm_ctx,
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 mm_struct *mm = vma->vm_mm;
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);
up_read(&mm->mmap_sem);
*prev = NULL; /* We wait for ACK w/o the mmap semaphore */
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(&mm->mmap_sem);
}
static int userfaultfd_release(struct inode *inode, struct file *file)
{
struct userfaultfd_ctx *ctx = file->private_data;