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REMAP_FILE_PAGES(2)        Linux Programmer's Manual       REMAP_FILE_PAGES(2)



NAME
       remap_file_pages - create a non-linear file mapping

SYNOPSIS
       #define _GNU_SOURCE
       #include <sys/mman.h>

       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 mapping, 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 addi-
       tional 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 correspondence 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 mapping 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 support 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 3.22 of the Linux man-pages project.  A description of the project, and informa-
       tion about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



Linux                             2008-04-22               REMAP_FILE_PAGES(2)