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       remap_file_pages - create a non-linear file mapping


       #include <sys/mman.h>

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


       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  additional  VMA
       (Virtual Memory Area) data structures.

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

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

       The  values  specified  in  start  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(), 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 appropriately.


       The remap_file_pages() system call appeared in Linux 2.5.46.


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

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


       The remap_file_pages() system call is Linux specific.


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