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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | STANDARDS | HISTORY | SEE ALSO | COLOPHON |
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UFFDIO_MOVE(2const) UFFDIO_MOVE(2const)
UFFDIO_MOVE - atomically move a continuous memory chunk into the
userfault registered range
Standard C library (libc, -lc)
#include <linux/userfaultfd.h> /* Definition of UFFD* constants */
#include <sys/ioctl.h>
int ioctl(int fd, UFFDIO_MOVE, struct uffdio_move *argp);
#include <linux/userfaultfd.h>
struct uffdio_move {
__u64 dst; /* Destination of move */
__u64 src; /* Source of move */
__u64 len; /* Number of bytes to move */
__u64 mode; /* Flags controlling behavior of move */
__s64 move; /* Number of bytes moved, or negated error */
};
Atomically move a continuous memory chunk into the userfault
registered range and optionally wake up the blocked thread.
The following value may be bitwise ORed in .mode to change the
behavior of the UFFDIO_MOVE operation:
UFFDIO_MOVE_MODE_DONTWAKE
Do not wake up the thread that waits for page-fault
resolution
UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES
Allow holes in the source virtual range that is being
moved. When not specified, the holes will result in ENOENT
error. When specified, the holes will be accounted as
successfully moved memory. This is mostly useful to move
hugepage aligned virtual regions without knowing if there
are transparent hugepages in the regions or not, but
preventing the risk of having to split the hugepage during
the operation.
The .move field is used by the kernel to return the number of
bytes that was actually moved, or an error (a negated errno-style
value). The .move field is output-only; it is not read by the
UFFDIO_MOVE operation.
On success, 0 is returned. In this case, the entire area was
moved.
On error, -1 is returned and errno is set to indicate the error.
EAGAIN The number of bytes moved (i.e., the value returned in the
.move field) does not equal the value that was specified in
the .len field.
EINVAL Either .dst or .len was not a multiple of the system page
size, or the range specified by .src and .len or .dst and
.len was invalid.
EINVAL An invalid bit was specified in the .mode field.
ENOENT The source virtual memory range has unmapped holes and
UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES is not set.
EEXIST The destination virtual memory range is fully or partially
mapped.
EBUSY The pages in the source virtual memory range are either
pinned or not exclusive to the process. Once KSM
deduplicates pages or fork(2) COW-shares pages during
fork(2) with child processes, they are no longer exclusive.
The kernel might only perform lightweight checks for
detecting whether the pages are exclusive. To make the
operation more likely to succeed, KSM should be disabled,
fork(2) should be avoided or MADV_DONTFORK should be
configured for the source virtual memory area before
fork(2).
ENOMEM Allocating memory needed for the operation failed.
ESRCH The target process has exited at the time of a UFFDIO_MOVE
operation.
Linux.
Linux 6.8.
ioctl(2), ioctl_userfaultfd(2), userfaultfd(2)
linux.git/Documentation/admin-guide/mm/userfaultfd.rst
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.15.tar.gz
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⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2025-08-11. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
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part of the original manual page), send a mail to
man-pages@man7.org
Linux man-pages 6.15 2025-05-17 UFFDIO_MOVE(2const)
Pages that refer to this page: ioctl_userfaultfd(2)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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