Signed-off-by: Muhammad Usama Anjum <usama.anjum@xxxxxxxxxxxxx> --- The feature has been added to mm-stable: https://lore.kernel.org/all/20231018213453.BF1ACC43395@xxxxxxxxxxxxxxx Changes since v1: - Several formatting updates - Added some additional sentences --- man2/ioctl_pagemap_scan.2 | 203 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 203 insertions(+) create mode 100644 man2/ioctl_pagemap_scan.2 diff --git a/man2/ioctl_pagemap_scan.2 b/man2/ioctl_pagemap_scan.2 new file mode 100644 index 000000000..c257072d7 --- /dev/null +++ b/man2/ioctl_pagemap_scan.2 @@ -0,0 +1,203 @@ +.\" This manpage is Copyright (C) 2023 Collabora; +.\" Written by Muhammad Usama Anjum <usama.anjum@xxxxxxxxxxxxx> +.\" +.\" SPDX-License-Identifier: Linux-man-pages-copyleft +.\" +.TH ioctl_pagemap_scan 2 2023-10-17 "Linux man-pages (unreleased)" +.SH NAME +ioctl_pagemap_scan \- get and/or clear page flags +.SH LIBRARY +Standard C library +.RI ( libc ", " \-lc ) +.SH SYNOPSIS +.nf +.BR "#include <linux/fs.h>" " /* Definition of " struct " " pm_scan_arg ", " +.BR " struct page_region "and " PAGE_IS_* "constants " */" +.B #include <sys/ioctl.h> +.PP +.BI "int ioctl(int " pagemap_fd ", PAGEMAP_SCAN, struct pm_scan_arg *" arg ); +.fi +.SH DESCRIPTION +This +.BR ioctl (2) +is used to get and optionally clear some specific flags from page table entries. +The information is returned with +.B PAGE_SIZE +granularity. +.PP +To start tracking the written state (flag) of a page or range of memory, +the +.B UFFD_FEATURE_WP_ASYNC +must be enabled by +.B UFFDIO_API +.BR ioctl (2) +on +.B userfaultfd +and memory range must be registered with +.B UFFDIO_REGISTER +.BR ioctl (2) +in +.B UFFDIO_REGISTER_MODE_WP +mode. +.SS Supported page flags +The following page table entry flags are supported: +.TP +.B PAGE_IS_WPALLOWED +The page has asynchronous write-protection enabled. +.TP +.B PAGE_IS_WRITTEN +The page has been written to from the time it was write protected. +.TP +.B PAGE_IS_FILE +The page is file backed. +.TP +.B PAGE_IS_PRESENT +The page is present in the memory. +.TP +.B PAGE_IS_SWAPPED +The page is swapped. +.TP +.B PAGE_IS_PFNZERO +The page has zero PFN. +.TP +.B PAGE_IS_HUGE +The page is THP or Hugetlb backed. +.SS Supported operations +The get operation is always performed +if the output buffer is specified. +The other operations are as following: +.TP +.B PM_SCAN_WP_MATCHING +Write protect the matched pages. +.TP +.B PM_SCAN_CHECK_WPASYNC +Abort the scan +when a page is found +which doesn't have the Userfaultfd Asynchronous Write protection enabled. +.SS The \f[I]struct pm_scan_arg\f[] argument +.EX +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; +}; +.EE +.TP +.B size +This field should be set to the size of the structure in bytes, +as in +.IR "sizeof(struct pm_scan_arg)" . +.TP +.B flags +The operations to be performed are specified in it. +.TP +.B start +The starting address of the scan is specified in it. +.TP +.B end +The ending address of the scan is specified in it. +.TP +.B walk_end +The kernel returns the scan's ending address in it. +The +.I walk_end +equal to +.I end +means that scan has completed on the entire range. +.TP +.B vec +The address of +.I page_region +array for output. +.PP +.in +8n +.EX +struct page_region { + __u64 start; + __u64 end; + __u64 categories; +}; +.EE +.in +.TP +.B vec_len +The length of the +.I page_region +struct array. +.TP +.B max_pages +It is the optional limit for the number of output pages required. +.TP +.B category_inverted +.BI PAGE_IS_ * +categories which values match if 0 instead of 1. +.TP +.B category_mask +Skip pages for which any +.BI PAGE_IS_ * +category doesn't match. +.TP +.B category_anyof_mask +Skip pages for which no +.BI PAGE_IS_ * +category matches. +.TP +.B return_mask +.BI PAGE_IS_ * +categories that are to be reported in +.IR page_region . +.SH RETURN VALUE +On error, \-1 is returned, and +.I errno +is set to indicate the error. +.SH ERRORS +Error codes can be one of, but are not limited to, the following: +.TP +.B EINVAL +Invalid arguments i.e., invalid +.I size +of the argument, invalid +.IR flags , +invalid +.IR categories , +the +.I start +address isn't aligned with +.B PAGE_SIZE +or +.I vec_len +is specified when +.I vec +is +.BR NULL . +.TP +.B EFAULT +Invalid +.I arg +pointer, invalid +.I vec +pointer or invalid address range specified by +.I start +and +.IR end . +.TP +.B ENOMEM +No memory is available. +.TP +.B EINTR +Fetal signal is pending. +.SH STANDARDS +Linux. +.SH HISTORY +Linux 6.7. +.SH SEE ALSO +.BR ioctl (2) -- 2.42.0
