text: /*
   * 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)
   * 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"
  #include <sys/param.h>
  #include <sys/vnode.h>
  
  
  #include "afs/sysincludes.h"	/* Standard vendor system headers */
  #include "afsincludes.h"	/* Afs-based standard headers */
  #include "afs/afs_stats.h"	/* statistics */
  #include <vm/vm_object.h>
  #include <vm/vm_map.h>
  #include <sys/limits.h>
  #if __FreeBSD_version >= 1000030
  #include <sys/rwlock.h>
  #endif
  
  /*
   * FreeBSD implementation notes:
   * Most of these operations require us to frob vm_objects.  Most
   * functions require that the object be locked (with VM_OBJECT_*LOCK)
   * on entry and leave it locked on exit.  The locking protocol
   * requires that we access vp->v_object with the heavy vnode lock
   * held and the vnode interlock unlocked.
   *
   * The locking protocol for vnodes is defined in
   * kern/vnode_if.src and sys/vnode.h; unfortunately, it is not *quite*
   * constant from version to version so to be properly correct we must
   * check the VCS history of those files.
   */
  
  #define	lock_vnode(v, f)	vn_lock((v), (f))
  #define ilock_vnode(v)	vn_lock((v), LK_INTERLOCK|LK_EXCLUSIVE|LK_RETRY)
  #define unlock_vnode(v)	VOP_UNLOCK((v), 0)
  #define islocked_vnode(v)	VOP_ISLOCKED((v))
  
  #if __FreeBSD_version >= 1000030
  #define AFS_VM_OBJECT_WLOCK(o)	VM_OBJECT_WLOCK(o)
  #define AFS_VM_OBJECT_WUNLOCK(o)	VM_OBJECT_WUNLOCK(o)
  #else
  #define AFS_VM_OBJECT_WLOCK(o)	VM_OBJECT_LOCK(o)
  #define AFS_VM_OBJECT_WUNLOCK(o)	VM_OBJECT_UNLOCK(o)
  #endif
  
  /* 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. It must not be dropped.
   *
   */
  int
  osi_VM_FlushVCache(struct vcache *avc)
  {
      struct vnode *vp;
      int code;
  
      vp = AFSTOV(avc);
  
      VI_LOCK(vp);
      code = osi_fbsd_checkinuse(avc);
      if (code) {
  	VI_UNLOCK(vp);
  	return code;
      }
  
      /* must hold the vnode before calling cache_purge()
       * This code largely copied from vfs_subr.c:vlrureclaim() */
      vholdl(vp);
      VI_UNLOCK(vp);
  
      AFS_GUNLOCK();
      cache_purge(vp);
      AFS_GLOCK();
  
      vdrop(vp);
  
      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(struct vcache *avc)
  {
      struct vnode *vp;
      struct vm_object *obj;
      int anyio, tries;
  
      ReleaseWriteLock(&avc->lock);
      AFS_GUNLOCK();
      tries = 5;
      vp = AFSTOV(avc);
  
      /*
       * I don't understand this.  Why not just call vm_object_page_clean()
       * and be done with it?  I particularly don't understand why we're calling
       * vget() here.  Is there some reason to believe that the vnode might
       * be being recycled at this point?  I don't think there's any need for
       * this loop, either -- if we keep the vnode locked all the time,
       * that and the object lock will prevent any new pages from appearing.
       * The loop is what causes the race condition.  -GAW
       */
      do {
  	anyio = 0;
  	
  	obj = vp->v_object;
  	if (obj != NULL && obj->flags & OBJ_MIGHTBEDIRTY) {
  	    if (!vget(vp, LK_EXCLUSIVE | LK_RETRY, curthread)) {
  		    obj = vp->v_object;
  		    if (obj != NULL) {
  			AFS_VM_OBJECT_WLOCK(obj);
  			vm_object_page_clean(obj, 0, 0, OBJPC_SYNC);
  			AFS_VM_OBJECT_WUNLOCK(obj);
  			anyio = 1;
  		    }
  		    vput(vp);
  		}
  	    }
      } 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(struct vcache *avc, afs_ucred_t *acred, int sync)
  {
      struct vnode *vp;
      int tries, code;
      int islocked;
  
      vp = AFSTOV(avc);
  
      VI_LOCK(vp);
      if (vp->v_iflag & VI_DOOMED) {
  	VI_UNLOCK(vp);
  	return;
      }
      VI_UNLOCK(vp);
  
      AFS_GUNLOCK();
  
      islocked = islocked_vnode(vp);
      if (islocked == LK_EXCLOTHER)
  	panic("Trying to Smush over someone else's lock");
      else if (islocked == LK_SHARED) {
  	afs_warn("Trying to Smush with a shared lock");
  	lock_vnode(vp, LK_UPGRADE);
      } else if (!islocked)
  	lock_vnode(vp, LK_EXCLUSIVE);
  
      if (vp->v_bufobj.bo_object != NULL) {
  	AFS_VM_OBJECT_WLOCK(vp->v_bufobj.bo_object);
  	/*
  	 * Do we really want OBJPC_SYNC?  OBJPC_INVAL would be
  	 * faster, if invalidation is really what we are being
  	 * asked to do.  (It would make more sense, too, since
  	 * otherwise this function is practically identical to
  	 * osi_VM_StoreAllSegments().)  -GAW
  	 */
  
  	/*
  	 * Dunno.  We no longer resemble osi_VM_StoreAllSegments,
  	 * though maybe that's wrong, now.  And OBJPC_SYNC is the
  	 * common thing in 70 file systems, it seems.  Matt.
  	 */
  
  	vm_object_page_clean(vp->v_bufobj.bo_object, 0, 0, OBJPC_SYNC);
  	AFS_VM_OBJECT_WUNLOCK(vp->v_bufobj.bo_object);
      }
  
      tries = 5;
      code = osi_vinvalbuf(vp, V_SAVE, PCATCH, 0);
      while (code && (tries > 0)) {
  	afs_warn("TryToSmush retrying vinvalbuf");
  	code = osi_vinvalbuf(vp, V_SAVE, PCATCH, 0);
  	--tries;
      }
      if (islocked == LK_SHARED)
  	lock_vnode(vp, LK_DOWNGRADE);
      else if (!islocked)
  	unlock_vnode(vp);
  
      AFS_GLOCK();
  }
  
  /* 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, afs_ucred_t *credp)
  {
      struct vnode *vp;
      struct vm_object *obj;
  
      vp = AFSTOV(avc);
      ASSERT_VOP_LOCKED(vp, __func__);
      obj = vp->v_object;
      if (obj != NULL) {
  	AFS_VM_OBJECT_WLOCK(obj);
  	vm_object_page_remove(obj, 0, 0, FALSE);
  	AFS_VM_OBJECT_WUNLOCK(obj);
      }
      osi_vinvalbuf(vp, 0, 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(struct vcache *avc, int alen, afs_ucred_t *acred)
  {
      vnode_pager_setsize(AFSTOV(avc), alen);
  }
  