NAME¶

UFFDIO_CONTINUE - resolve a minor page fault

LIBRARY¶

Standard C library (libc, -lc)

SYNOPSIS¶

#include <linux/userfaultfd.h>  /* Definition of UFFD* constants */
#include <sys/ioctl.h>

int ioctl(int fd, UFFDIO_CONTINUE, struct uffdio_continue *argp);

#include <linux/userfaultfd.h>

struct uffdio_continue {
    struct uffdio_range  range;


                     /* Range to install PTEs for and continue */
    __u64   mode;    /* Flags controlling the behavior of continue */
    __s64   mapped;  /* Number of bytes mapped, or negated error */
};

DESCRIPTION¶

Resolve a minor page fault by installing page table entries for existing pages in the page cache.

The following value may be bitwise ORed in mode to change the behavior of the UFFDIO_CONTINUE operation:

UFFDIO_CONTINUE_MODE_DONTWAKE

Do not wake up the thread that waits for page-fault resolution.

The mapped field is used by the kernel to return the number of bytes that were actually mapped, or an error in the same manner as UFFDIO_COPY. If the value returned in the mapped field doesn't match the value that was specified in range.len, the operation fails with the error EAGAIN. The mapped field is output-only; it is not read by the UFFDIO_CONTINUE operation.

RETURN VALUE¶

This ioctl(2) operation returns 0 on success. In this case, the entire area was mapped. On error, -1 is returned and errno is set to indicate the error.

ERRORS¶

EAGAIN

The number of bytes mapped (i.e., the value returned in the mapped field) does not equal the value that was specified in the range.len field.

EEXIST

One or more pages were already mapped in the given range.

EFAULT

No existing page could be found in the page cache for the given range.

EINVAL

Either range.start or range.len was not a multiple of the system page size; or range.len was zero; or the range specified was invalid.

EINVAL

An invalid bit was specified in the mode field.

ENOENT

The faulting process has changed its virtual memory layout simultaneously with an outstanding UFFDIO_CONTINUE operation.

ENOMEM

Allocating memory needed to setup the page table mappings failed.

ESRCH

The faulting process has exited at the time of a UFFDIO_CONTINUE operation.

STANDARDS¶

Linux.

HISTORY¶

Linux 5.13.

EXAMPLES¶

See userfaultfd(2).

SEE ALSO¶

ioctl(2), ioctl_userfaultfd(2), userfaultfd(2)

linux.git/Documentation/admin-guide/mm/userfaultfd.rst