minix/servers/vfs/vnode.c

/* This file contains the routines related to vnodes.
 * The entry points are:
 *      
 *  get_vnode - increase counter and get details of an inode
 *  get_free_vnode - get a pointer to a free vnode obj
 *  find_vnode - find a vnode according to the FS endpoint and the inode num.  
 *  dup_vnode - duplicate vnode (i.e. increase counter)
 *  put_vnode - drop vnode (i.e. decrease counter)  
 */

#include "fs.h"
#include "vnode.h"
#include "vmnt.h"
#include "fproc.h"
#include "file.h"
#include <minix/vfsif.h>

/* Is vnode pointer reasonable? */
#if NDEBUG
#define SANEVP(v)
#define CHECKVN(v)
#define ASSERTVP(v)
#else
#define SANEVP(v) ((((v) >= &vnode[0] && (v) < &vnode[NR_VNODES])))

#define BADVP(v, f, l) printf("%s:%d: bad vp %p\n", f, l, v)

/* vp check that returns 0 for use in check_vrefs() */
#define CHECKVN(v) if(!SANEVP(v)) {				\
	BADVP(v, __FILE__, __LINE__);	\
	return 0;	\
}

/* vp check that panics */
#define ASSERTVP(v) if(!SANEVP(v)) { \
	BADVP(v, __FILE__, __LINE__); panic("bad vp"); }
#endif

/*===========================================================================*
 *				get_free_vnode				     *
 *===========================================================================*/
PUBLIC struct vnode *get_free_vnode()
{
/* Find a free vnode slot in the vnode table (it's not actually allocated) */
  struct vnode *vp;

  for (vp = &vnode[0]; vp < &vnode[NR_VNODES]; ++vp) {
	if (vp->v_ref_count == 0) {
		vp->v_pipe = NO_PIPE;
		vp->v_uid  = -1;
		vp->v_gid  = -1;
		vp->v_sdev = NO_DEV;
		vp->v_mapfs_e = 0;
		vp->v_mapinode_nr = 0;
		return(vp);
	}
  } 

  err_code = ENFILE;
  return(NULL);
}


/*===========================================================================*
 *				find_vnode				     *
 *===========================================================================*/
PUBLIC struct vnode *find_vnode(int fs_e, int numb)
{
/* Find a specified (FS endpoint and inode number) vnode in the
 * vnode table */
  struct vnode *vp;

  for (vp = &vnode[0]; vp < &vnode[NR_VNODES]; ++vp)
	if (vp->v_ref_count > 0 && vp->v_inode_nr == numb && vp->v_fs_e == fs_e)
		return(vp);
  
  return(NULL);
}


/*===========================================================================*
 *				dup_vnode				     *
 *===========================================================================*/
PUBLIC void dup_vnode(struct vnode *vp)
{
/* dup_vnode() is called to increment the vnode and therefore the
 * referred inode's counter.
 */
  ASSERTVP(vp);
  vp->v_ref_count++;
}


/*===========================================================================*
 *				put_vnode				     *
 *===========================================================================*/
PUBLIC void put_vnode(struct vnode *vp)
{
/* Decrease vnode's usage counter and decrease inode's usage counter in the 
 * corresponding FS process. Decreasing the fs_count each time we decrease the
 * ref count would lead to poor performance. Instead, only decrease fs_count
 * when the ref count hits zero. However, this could lead to fs_count to wrap.
 * To prevent this, we drop the counter to 1 when the counter hits 256.
 * We maintain fs_count as a sanity check to make sure VFS and the FS are in
 * sync.
 */
  ASSERTVP(vp);

  if (vp->v_ref_count > 1) {
	/* Decrease counter */
	vp->v_ref_count--;
	if (vp->v_fs_count > 256) 
		vnode_clean_refs(vp);

	return;
  }

  /* A vnode that's not in use can't be put. */
  if (vp->v_ref_count <= 0) {
	printf("put_vnode: bad v_ref_count %d\n", vp->v_ref_count);
	panic("put_vnode failed");
  }

  /* fs_count should indicate that the file is in use. */
  if (vp->v_fs_count <= 0) {
	printf("put_vnode: bad v_fs_count %d\n", vp->v_fs_count);
	panic("put_vnode failed");
  }

  /* Tell FS we don't need this inode to be open anymore. */
  req_putnode(vp->v_fs_e, vp->v_inode_nr, vp->v_fs_count); 

  /* This inode could've been mapped. If so, tell PFS to close it as well. */
  if(vp->v_mapfs_e != 0  && vp->v_mapinode_nr != vp->v_inode_nr &&
     vp->v_mapfs_e != vp->v_fs_e) {
	req_putnode(vp->v_mapfs_e, vp->v_mapinode_nr, vp->v_mapfs_count); 
  }

  vp->v_fs_count = 0;
  vp->v_ref_count = 0;
  vp->v_pipe = NO_PIPE;
  vp->v_sdev = NO_DEV;
  vp->v_mapfs_e = 0;
  vp->v_mapinode_nr = 0;
  vp->v_mapfs_count = 0;
}


/*===========================================================================*
 *				vnode_clean_refs			     *
 *===========================================================================*/
PUBLIC void vnode_clean_refs(struct vnode *vp)
{
/* Tell the underlying FS to drop all reference but one. */

  if (vp == NULL) return;
  if (vp->v_fs_count <= 1) return;	/* Nothing to do */

  /* Drop all references except one */
  req_putnode(vp->v_fs_e, vp->v_inode_nr, vp->v_fs_count - 1);
  vp->v_fs_count = 1;
}


#define REFVP(v) { vp = (v); CHECKVN(v); vp->v_ref_check++; }

#if DO_SANITYCHECKS
/*===========================================================================*
 *				check_vrefs				     *
 *===========================================================================*/
PUBLIC int check_vrefs()
{
	int i, bad;
	int ispipe_flag, ispipe_mode;
	struct vnode *vp;
	struct vmnt *vmp;
	struct fproc *rfp;
	struct filp *f;

	/* Clear v_ref_check */
	for (vp = &vnode[0]; vp < &vnode[NR_VNODES]; ++vp)
		vp->v_ref_check= 0;

	/* Count reference for processes */
	for (rfp=&fproc[0]; rfp < &fproc[NR_PROCS]; rfp++) {
		if (rfp->fp_pid == PID_FREE)
			continue;
		if(rfp->fp_rd) REFVP(rfp->fp_rd);
                if(rfp->fp_wd) REFVP(rfp->fp_wd);
  	}

	/* Count references from filedescriptors */
	for (f = &filp[0]; f < &filp[NR_FILPS]; f++)
	{
		if (f->filp_count == 0)
			continue;
		REFVP(f->filp_vno);
	}

	/* Count references to mount points */
	for (vmp = &vmnt[0]; vmp < &vmnt[NR_MNTS]; ++vmp)
	{
		if (vmp->m_dev == NO_DEV)
			continue;
		REFVP(vmp->m_root_node);
		if(vmp->m_mounted_on)
			REFVP(vmp->m_mounted_on);
	}

	/* Check references */
	bad= 0;
	for (vp = &vnode[0]; vp < &vnode[NR_VNODES]; ++vp)
	{
		if (vp->v_ref_count != vp->v_ref_check)
		{
			printf(
"Bad reference count for inode %d on device 0x%x: found %d, listed %d\n",
				vp->v_inode_nr, vp->v_dev, vp->v_ref_check,
				vp->v_ref_count);
			printf("last marked at %s, %d\n",
				vp->v_file, vp->v_line);
			bad= 1;
		}

		/* Also check v_pipe */
		if (vp->v_ref_count != 0)
		{
			ispipe_flag= (vp->v_pipe == I_PIPE);
			ispipe_mode= ((vp->v_mode & I_TYPE) == I_NAMED_PIPE);
			if (ispipe_flag != ispipe_mode)
			{
				printf(
"Bad v_pipe for inode %d on device 0x%x: found %d, mode 0%o\n",
				vp->v_inode_nr, vp->v_dev, vp->v_pipe,
				vp->v_mode);
				printf("last marked at %s, %d\n",
					vp->v_file, vp->v_line);
				bad= 1;
			}
		}
	}
	return !bad;
}
#endif