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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | STANDARDS | HISTORY | SEE ALSO | COLOPHON |
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PAGEMAP_SCAN(2const) PAGEMAP_SCAN(2const)
PAGEMAP_SCAN - get and/or clear page flags
Standard C library (libc, -lc)
#include <linux/fs.h> /* Definition of PAGE* and PM_* constants */
#include <sys/ioctl.h>
int ioctl(int pagemap_fd, PAGEMAP_SCAN, struct pm_scan_arg *arg);
#include <linux/fs.h>
struct pm_scan_arg {
__u64 size;
__u64 flags;
__u64 start;
__u64 end;
__u64 walk_end;
__u64 vec;
__u64 vec_len;
__u64 max_pages;
__u64 category_inverted;
__u64 category_mask;
__u64 category_anyof_mask;
__u64 return_mask;
};
struct page_region {
__u64 start;
__u64 end;
__u64 categories;
};
This ioctl(2) is used to get and optionally clear some specific
flags from page table entries. The information is returned with
PAGE_SIZE granularity.
To start tracking the written state (flag) of a page or range of
memory, the UFFD_FEATURE_WP_ASYNC must be enabled by UFFDIO_API
ioctl(2) on userfaultfd and memory range must be registered with
UFFDIO_REGISTER ioctl(2) in UFFDIO_REGISTER_MODE_WP mode.
Supported page flags
The following page table entry flags are supported:
PAGE_IS_WPALLOWED
The page has asynchronous write-protection enabled.
PAGE_IS_WRITTEN
The page has been written to from the time it was write
protected.
PAGE_IS_FILE
The page is file backed.
PAGE_IS_PRESENT
The page is present in the memory.
PAGE_IS_SWAPPED
The page is swapped.
PAGE_IS_PFNZERO
The page has zero PFN.
PAGE_IS_HUGE
The page is THP or Hugetlb backed.
Supported operations
The get operation is always performed if the output buffer is
specified. The other operations are as following:
PM_SCAN_WP_MATCHING
Write protect the matched pages.
PM_SCAN_CHECK_WPASYNC
Abort the scan when a page is found which doesn't have the
Userfaultfd Asynchronous Write protection enabled.
The struct pm_scan_arg argument
size This field should be set to the size of the structure in
bytes, as in sizeof(struct pm_scan_arg).
flags The operations to be performed are specified in it.
start The starting address of the scan is specified in it.
end The ending address of the scan is specified in it.
walk_end
The kernel returns the scan's ending address in it. The
walk_end equal to end means that scan has completed on the
entire range.
vec The address of page_region array for output.
vec_len
The length of the page_region struct array.
max_pages
It is the optional limit for the number of output pages
required.
category_inverted
PAGE_IS_* categories which values match if 0 instead of 1.
category_mask
Skip pages for which any PAGE_IS_* category doesn't match.
category_anyof_mask
Skip pages for which no PAGE_IS_* category matches.
return_mask
PAGE_IS_* categories that are to be reported in
page_region.
On error, -1 is returned, and errno is set to indicate the error.
Error codes can be one of, but are not limited to, the following:
EINVAL Invalid arguments i.e., invalid size of the argument,
invalid flags, invalid categories, the start address isn't
aligned with PAGE_SIZE, or vec_len is specified when vec is
NULL.
EFAULT Invalid arg pointer, invalid vec pointer, or invalid
address range specified by start and end.
ENOMEM No memory is available.
EINTR Fetal signal is pending.
Linux.
Linux 6.7.
ioctl(2)
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
fetched from
⟨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-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
man-pages@man7.org
Linux man-pages 6.15 2025-05-17 PAGEMAP_SCAN(2const)
Pages that refer to this page: ioctl_fs(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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