REMAP_FILE_PAGES(2)	   Linux Programmers Manual	  REMAP_FILE_PAGES(2)



NAME
       remap_file_pages - create a non-linear file mapping

SYNOPSIS
       #define _GNU_SOURCE
       #include 

       int remap_file_pages(void *addr, size_t size, int prot,
			    ssize_t pgoff, int flags);

DESCRIPTION
       The  remap_file_pages() system call is used to create a non-linear map
       ping, that is, a mapping in which the pages of the file are mapped into
       a   non-sequential   order   in	 memory.    The   advantage  of  using
       remap_file_pages() over using repeated calls to	mmap(2)  is  that  the
       former  approach  does  not require the kernel to create additional VMA
       (Virtual Memory Area) data structures.

       To create a non-linear mapping we perform the following steps:

       1. Use mmap(2) to create a mapping (which is initially  linear).   This
	  mapping must be created with the MAP_SHARED flag.

       2. Use  one or more calls to remap_file_pages() to rearrange the corre
	  spondence between the pages of the mapping  and  the	pages  of  the
	  file.   It  is possible to map the same page of a file into multiple
	  locations within the mapped region.

       The pgoff and size arguments specify the region of the file that is  to
       be relocated within the mapping: pgoff is a file offset in units of the
       system page size; size is the length of the region in bytes.

       The addr argument serves two purposes.  First, it identifies  the  map
       ping  whose  pages we want to rearrange.  Thus, addr must be an address
       that falls within a region previously mapped  by  a  call  to  mmap(2).
       Second,	addr  specifies the address at which the file pages identified
       by pgoff and size will be placed.

       The values specified in addr and size should be multiples of the system
       page size.  If they are not, then the kernel rounds both values down to
       the nearest multiple of the page size.

       The prot argument must be specified as 0.

       The flags argument has the same meaning as for mmap(2), but  all  flags
       other than MAP_NONBLOCK are ignored.

RETURN VALUE
       On  success,  remap_file_pages()  returns 0.  On error, -1 is returned,
       and errno is set appropriately.

ERRORS
       EINVAL addr does  not  refer  to  a  valid  mapping  created  with  the
	      MAP_SHARED flag.

       EINVAL addr, size, prot, or pgoff is invalid.

VERSIONS
       The remap_file_pages() system call appeared in Linux 2.5.46; glibc sup
       port was added in version 2.3.3.

CONFORMING TO
       The remap_file_pages() system call is Linux-specific.

SEE ALSO
       getpagesize(2), mmap(2), mmap2(2),  mprotect(2),  mremap(2),  msync(2),
       feature_test_macros(7)

COLOPHON
       This  page  is  part of release 3.05 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.



Linux				  2008-04-22		   REMAP_FILE_PAGES(2)