userfaultfd: replace ENOSPC with ESRCH in case mm has gone during copy/zeropage

When the process exit races with outstanding mcopy_atomic, it would be
better to return ESRCH error.  When such race occurs the process and
it's mm are going away and returning "no such process" to the uffd
monitor seems better fit than ENOSPC.

Link: http://lkml.kernel.org/r/1502111545-32305-1-git-send-email-rppt@linux.vnet.ibm.com
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Suggested-by: Michal Hocko <mhocko@suse.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Pavel Emelyanov <xemul@virtuozzo.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 06ea26b8c996f3cc7a9d6fd177260f89394fb325..b0d5897bc4e6d0e019c79f65b6d41df1d3b0d050 100644 (file)
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -1600,7 +1600,7 @@ static int userfaultfd_copy(struct userfaultfd_ctx *ctx,
                                   uffdio_copy.len);
                mmput(ctx->mm);
        } else {
-               return -ENOSPC;
+               return -ESRCH;
        }
        if (unlikely(put_user(ret, &user_uffdio_copy->copy)))
                return -EFAULT;
@@ -1647,7 +1647,7 @@ static int userfaultfd_zeropage(struct userfaultfd_ctx *ctx,
                                     uffdio_zeropage.range.len);
                mmput(ctx->mm);
        } else {
-               return -ENOSPC;
+               return -ESRCH;
        }
        if (unlikely(put_user(ret, &user_uffdio_zeropage->zeropage)))
                return -EFAULT;