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       remap_file_pages - create a nonlinear file mapping


       #define _GNU_SOURCE         /* See feature_test_macros(7) */
       #include <sys/mman.h>

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


       The  remap_file_pages()  system  call  is  used  to create a nonlinear mapping, that is, a
       mapping in which the pages of the file are mapped into a nonsequential  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 nonlinear 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

       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.


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


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

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


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


       The remap_file_pages() system call is Linux-specific.


       getpagesize(2), mmap(2), mmap2(2), mprotect(2), mremap(2), msync(2)


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