/* Copyright (C) 1998 Transarc Corporation - All rights reserved. */
/*
 * (C) COPYRIGHT IBM CORPORATION 1987, 1988
 * LICENSED MATERIALS - PROPERTY OF IBM
 */

#include "../afs/param.h"	/* Should be always first */
#include "../afs/sysincludes.h"	/* Standard vendor system headers */
#include "../afs/afsincludes.h"	/* Afs-based standard headers */
#include "../afs/afs_stats.h"	/* statistics */

/* Linux VM operations
 *
 * The general model for Linux is to treat vm as a cache that's:
 * 1) explicitly updated by AFS when AFS writes the data to the cache file.
 * 2) reads go through the cache. A cache miss is satisfied by the filesystem.
 *
 * This means flushing VM is not required on this OS.
 */

/* Try to discard pages, in order to recycle a vcache entry.
 *
 * We also make some sanity checks:  ref count, open count, held locks.
 *
 * We also do some non-VM-related chores, such as releasing the cred pointer
 * (for AIX and Solaris) and releasing the gnode (for AIX).
 *
 * Locking:  afs_xvcache lock is held.  If it is dropped and re-acquired,
 *   *slept should be set to warn the caller.
 *
 * Formerly, afs_xvcache was dropped and re-acquired for Solaris, but now it
 * is not dropped and re-acquired for any platform.  It may be that *slept is
 * therefore obsolescent.
 */
int osi_VM_FlushVCache(struct vcache *avc, int *slept)
{
    struct inode *ip = (struct inode*)avc;

    if (avc->vrefCount != 0)
	return EBUSY;

    if (avc->opens != 0)
	return EBUSY;

    invalidate_inode_pages(ip);
    return 0;
}

/* Try to invalidate pages, for "fs flush" or "fs flushv"; or
 * try to free pages, when deleting a file.
 *
 * Locking:  the vcache entry's lock is held.  It may be dropped and 
 * re-obtained.
 *
 * Since we drop and re-obtain the lock, we can't guarantee that there won't
 * be some pages around when we return, newly created by concurrent activity.
 */
void osi_VM_TryToSmush(struct vcache *avc, struct AFS_UCRED *acred, int sync)
{
    invalidate_inode_pages((struct inode *)avc);
}

/* Flush and invalidate pages, for fsync() with INVAL flag
 *
 * Locking:  only the global lock is held.
 */
void osi_VM_FSyncInval(struct vcache *avc)
{

}

/* Try to store pages to cache, in order to store a file back to the server.
 *
 * Locking:  the vcache entry's lock is held.  It will usually be dropped and
 * re-obtained.
 */
void osi_VM_StoreAllSegments(struct vcache *avc)
{

}

/* Purge VM for a file when its callback is revoked.
 *
 * Locking:  No lock is held, not even the global lock.
 */
void osi_VM_FlushPages(struct vcache *avc, struct AFS_UCRED *credp)
{
    invalidate_inode_pages((struct inode*)avc);
}

/* Purge pages beyond end-of-file, when truncating a file.
 *
 * Locking:  no lock is held, not even the global lock.
 * activeV is raised.  This is supposed to block pageins, but at present
 * it only works on Solaris.
 */
void osi_VM_Truncate(struct vcache *avc, int alen, struct AFS_UCRED *acred)
{
    invalidate_inode_pages((struct inode*)avc);
}