'\" t
.\"     Title: get_user_pages_fast
.\"    Author: [FIXME: author] [see http://docbook.sf.net/el/author]
.\" Generator: DocBook XSL Stylesheets v1.79.1 <http://docbook.sf.net/>
.\"      Date: January 2017
.\"    Manual: Memory Management in Linux
.\"    Source: Kernel Hackers Manual 4.8.15
.\"  Language: English
.\"
.TH "GET_USER_PAGES_FAST" "9" "January 2017" "Kernel Hackers Manual 4\&.8\&." "Memory Management in Linux"
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.SH "NAME"
get_user_pages_fast \- pin user pages in memory
.SH "SYNOPSIS"
.HP \w'int\ get_user_pages_fast('u
.BI "int get_user_pages_fast(unsigned\ long\ " "start" ", int\ " "nr_pages" ", int\ " "write" ", struct\ page\ **\ " "pages" ");"
.SH "ARGUMENTS"
.PP
\fIstart\fR
.RS 4
starting user address
.RE
.PP
\fInr_pages\fR
.RS 4
number of pages from start to pin
.RE
.PP
\fIwrite\fR
.RS 4
whether pages will be written to
.RE
.PP
\fIpages\fR
.RS 4
array that receives pointers to the pages pinned\&. Should be at least nr_pages long\&.
.RE
.SH "DESCRIPTION"
.PP
Returns number of pages pinned\&. This may be fewer than the number requested\&. If nr_pages is 0 or negative, returns 0\&. If no pages were pinned, returns \-errno\&.
.PP
get_user_pages_fast provides equivalent functionality to get_user_pages, operating on current and current\->mm, with force=0 and vma=NULL\&. However unlike get_user_pages, it must be called without mmap_sem held\&.
.PP
get_user_pages_fast may take mmap_sem and page table locks, so no assumptions can be made about lack of locking\&. get_user_pages_fast is to be implemented in a way that is advantageous (vs
\fBget_user_pages\fR) when the user memory area is already faulted in and present in ptes\&. However if the pages have to be faulted in, it may turn out to be slightly slower so callers need to carefully consider what to use\&. On many architectures, get_user_pages_fast simply falls back to get_user_pages\&.
.SH "COPYRIGHT"
.br