FS_OPENPAGEFILE - Create paging file and handle

Purpose   

Creates/opens the paging file for the Pager. 

Calling Sequence   

int far pascal FS_OPENPAGEFILE(pFlags, pcMaxReq, pName, psffsi, psffsd,
                               usOpenMode, usOpenFlag, usAttr, Reserved)

unsigned long far * pFlag;
unsigned long far * pcMaxReq;
char far * pName;
struct sffsi far * psffsi;
struct sffsd far * psffsi;
unsigned short usOpenMode;
unsigned short usOpenFlag;
unsigned short usAttr;
unsigned long Reserved;

Where   

pFlag is a pointer to a flag double word for passing of information 
between the pager and the file system. 

pFlag == 0x00000001 indicates first open of the page file. 
pFlag == 0x00004000 indicates physical addresses are required in the page 
list . 
pFlag == 0x00008000 indicates 16:16 virtual addresses are required in the 
page list. 

All other values are reserved. 

pcMaxReq is a pointer to a unsigned long where the FSD places the maximum 
request list length that can be managed by an enhanced strategy device 
driver. 

pName is a pointer to the ASCIIZ path and filename of the paging file. 

psffsi is a pointer to the file-system-independent portion of an open file 
instance. 

psffsd is a pointer to the file-system-dependent portion of an open file 
instance. 

usOpenMode indicates the desired sharing mode and access mode for the file 
handle. 

See OS/2 Version 2.0 Control Program Programming Reference for a 
description of the OpenMode parameter for DosOpen. 

usOpenFlag indicates the action taken when the file is present or absent. 

See OS/2 Version 2.0 Control Program Programming Reference for a 
description of the usOpenFlag parameter for DosOpen. 

usAttr are the OS/2 file attributes. 

Reserved is a double word parameter reserved for use in the future. 
  

Remarks   

Enough information is provided for the FSD to perform a 'normal' open 
/create call. 

Since a page file has special requirements about contiguity of its 
allocations, FS_OPENPAGEFILE must assure that any data sectors allocated 
are returned ( Create call only). FS_ALLOCATEPAGESPACE will be called to 
handle file allocation . 

If the FSD cannot support the FS_DOPAGEIO (usually due to an disk device 
driver which does not support the Extended strategy entry point), the FSD 
can return zero (0) for *pcMaxReq. This tells the kernel file system that 
it must emulate FS_DOPAGEIO. 

The FSD can require either physical or virtual (16:16) addresses for 
subsequent calls to FS_DOPAGEIO. This allows an FSD to emulate FS_DOPAGEIO 
without having to worry about dealing with physical addresses. 

For a detailed description of the Extended Strategy request interface 
please see the OS/2 Version 2.0 Physical Device Driver Reference.