IFS - FS Helper Functions

Installable File Systems for OS/2
Installable File System Mechanism Installable File System Overview Extended Attributes FSD File Image FSD Initialization IFS Commands File System Function Calls FSD System Interfaces FSD Calling Conventions and Requirements FS Service Routines FS Helper Functions Remote IPL / Bootable IFS mini-FDS Entry Points mini-FDS Helper Routines

Reprint Courtesy of International Business Machines Corporation, © International Business Machines Corporation

The following table summarizes the routines that make up the File System Helper interface between FSDs and the kernel.

FS Helper Routine	Description
FSH_ADDSHARE	Add a name to the sharing set
FSH_BUFSTATE	REMOVED in OS/2 Version 2.0
FSH_CALLDRIVER	Call Device Driver's Extended Strategy entry point
FSH_CANONICALIZE	Convert pathname to canonical form
FSH_CHECKEANAME	Check EA name validity
FSH_CRITERROR	Signal a hard error to the daemon
FSH_DEVIOCTL	Send IOCTL request to device driver
FSH_DOVOLIO	Volume-based sector-oriented transfer
FSH_DOVOLIO2	Send volume-based IOCTL request to device driver.
FSH_FINDCHAR	Find first occurrence of char in string
FSH_FINDDUPHVPB	Locates equivalent hVPBs
FSH_FLUSHBUF	REMOVED in OS/2 Version 2.0
FSH_FORCENOSWAP	Force segments permanently into memory
FSH_GETBUF	REMOVED in OS/2 Version 2.0
FSH_GETFIRSTOVERLAPB	REMOVED in OS/2 Version 2.0
FSH_GETPRIORITY	Get current thread's I/O priority
FSH_GETVOLPARM	Get VPB data from VPB handle
FSH_INTERR	Signal an internal error
FSH_IOBOOST	Gives the current thread an I/O priority boost
FSH_IOSEMCLEAR	Clear an I/O-event semaphore
FSH_ISCURDIRPREFIX	Test for a prefix of a current directory
FSH_LOADCHAR	Load character from a string
FSH_NAMEFROMSFN	Get the full path name from an SFN
FSH_PREVCHAR	Move backward in string
FSH_PROBEBUF	User address validity check
FSH_QSYSINFO	Query system information
FSH_REGISTERPERFCTRS	Register a FSD with PERFVIEW
FSH_RELEASEBUF	REMOVED in OS/2 Version 2.0
FSH_REMOVESHARE	Remove a name from the sharing set
FSH_SEGALLOC	Allocate a GDT or LDT segment
FSH_SEGFREE	Release a GDT or LDT segment
FSH_SEGREALLOC	Change segment size
FSH_SEMCLEAR	Clear a semaphore
FSH_SEMREQUEST	Request a semaphore
FSH_SEMSET	Set a semaphore
FSH_SEMSETWAIT	Set a semaphore and wait for clear
FSH_SEMWAIT	Wait for clear
FSH_SETVOLUME	force a volume to be mounted on the drive
FSH_STORECHAR	Store character into string
FSH_UPPERCASE	Uppercase ASCIIZ string
FSH_WILDMATCH	Match using OS/2 wildcards
FSH_YIELD	Yield CPU to higher priority threads

FSDs are loaded as dynamic link libraries and may import services provided by the kernel. These services can be called directly by the file system, passing the relevant parameters.

No validation of input parameters is done unless otherwise specified. The FSD calls FSH_PROBEBUF, where appropriate, before calling the FS help routine.

When any service returns an error code, the FSD must return to the caller as soon as possible and return the specific error code from the helper to the FS router.

There are many deadlocks that may occur as a result of operations issued by FSDs. OS/2 provides no means whereby deadlocks between file systems and applications can be detected.