/*
 * Copyright 2000, International Business Machines Corporation and others.
 * All Rights Reserved.
 * 
 * This software has been released under the terms of the IBM Public
 * License.  For details, see the LICENSE file in the top-level source
 * directory or online at http://www.openafs.org/dl/license10.html
 */


/* osi_vm.c implements:
 *
 * osi_VM_FlushVCache(avc, slept)
 * osi_ubc_flush_dirty_and_wait(vp, flags)
 * osi_VM_StoreAllSegments(avc)
 * osi_VM_TryToSmush(avc, acred, sync)
 * osi_VM_FlushPages(avc, credp)
 * osi_VM_Truncate(avc, alen, acred)
 */

#include <afsconfig.h>
#include "../afs/param.h"

RCSID("$Header$");

#include "../afs/sysincludes.h"	/* Standard vendor system headers */
#include "../afs/afsincludes.h"	/* Afs-based standard headers */
#include "../afs/afs_stats.h"  /* statistics */
#include <vm/vm_object.h>
#include <vm/vm_map.h>
#include <limits.h>
#include <float.h>

/* 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.
 *
 * OSF/1 Locking:  VN_LOCK has been called.
 */
int
osi_VM_FlushVCache(avc, slept)
    struct vcache *avc;
    int *slept;
{
    struct vm_object *obj;
    struct vnode *vp;
    if (VREFCOUNT(avc) > 1)
	return EBUSY;

    if (avc->opens)
	return EBUSY;

    /* if a lock is held, give up */
    if (CheckLock(&avc->lock) || afs_CheckBozonLock(&avc->pvnLock))
	return EBUSY;

    AFS_GUNLOCK();
    vp=avc;
    simple_lock(&vp->v_interlock);
    if (VOP_GETVOBJECT(vp, &obj) == 0) {
       vm_object_page_remove(obj, 0, 0, FALSE);
#if 0
        if (obj->ref_count == 0) {
           vgonel(vp,curproc);
           simple_lock(&vp->v_interlock);
           vp->v_tag=VT_AFS;
           SetAfsVnode(vp);
        }
#endif
    } 
    simple_unlock(&vp->v_interlock);
    AFS_GLOCK();

    return 0;
}

/* 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(avc)
    struct vcache *avc;
{
    struct vnode *vp;
    struct vm_object *obj;
    int anyio,tries;
    ReleaseWriteLock(&avc->lock);
    AFS_GUNLOCK();
    tries=5;
    vp=avc;
    do {
    anyio=0;
    simple_lock(&vp->v_interlock);
    if (VOP_GETVOBJECT(vp, &obj) == 0 &&
       (obj->flags & OBJ_MIGHTBEDIRTY)) {
        if (!vget(vp,
            LK_INTERLOCK | LK_EXCLUSIVE | LK_RETRY | LK_NOOBJ, curproc)) {
            if (VOP_GETVOBJECT(vp, &obj) == 0) {
               vm_object_page_clean(obj, 0, 0, OBJPC_SYNC);
               anyio = 1;
            }
            vput(vp);
        }
    } else {
        simple_unlock(&vp->v_interlock);
    }
    } while (anyio && (--tries > 0));
    AFS_GLOCK();
    ObtainWriteLock(&avc->lock,94);
}

/* 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(avc, acred, sync)
    struct vcache *avc;
    struct AFS_UCRED *acred;
    int sync;
{
    struct vnode *vp;
    struct vm_object *obj;
    int anyio, tries;
    ReleaseWriteLock(&avc->lock);
    AFS_GUNLOCK();
    tries=5;
    vp=avc;
    do {
       anyio=0;
       simple_lock(&vp->v_interlock);
       if (VOP_GETVOBJECT(vp, &obj) == 0 &&
          (obj->flags & OBJ_MIGHTBEDIRTY)) {
           if (!vget(vp,
               LK_INTERLOCK | LK_EXCLUSIVE | LK_RETRY | LK_NOOBJ, curproc)) {
               if (VOP_GETVOBJECT(vp, &obj) == 0) {
                  vm_object_page_clean(obj, 0, 0, OBJPC_SYNC);
                  anyio = 1;
               }
               vput(vp);
           }
       } else {
           simple_unlock(&vp->v_interlock);
       }
    } while (anyio && (--tries > 0));
    simple_lock(&vp->v_interlock);
    if (VOP_GETVOBJECT(vp, &obj) == 0) {
       vm_object_page_remove(obj, 0, 0, FALSE);
    }
    simple_unlock(&vp->v_interlock);
    /*vinvalbuf(AFSTOV(avc),0, NOCRED, curproc, 0,0);*/
    AFS_GLOCK();
    ObtainWriteLock(&avc->lock,59);
}

/* Purge VM for a file when its callback is revoked.
 *
 * Locking:  No lock is held, not even the global lock.
 */
void
osi_VM_FlushPages(avc, credp)
    struct vcache *avc;
    struct AFS_UCRED *credp;
{
    struct vnode *vp;
    struct vm_object *obj;
    vp=avc;
    simple_lock(&vp->v_interlock);
    if (VOP_GETVOBJECT(vp, &obj) == 0) {
       vm_object_page_remove(obj, 0, 0, FALSE);
    }
    simple_unlock(&vp->v_interlock);
    /*vinvalbuf(AFSTOV(avc),0, NOCRED, curproc, 0,0);*/
}

/* 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(avc, alen, acred)
    struct vcache *avc;
    int alen;
    struct AFS_UCRED *acred;
{
    vnode_pager_setsize(AFSTOV(avc), alen);
}