inode.c

Minix3.11的源码。[MINIX 3是一个为高可靠性应用而设计的自由且简洁的类UNIX系统。]

/* This file manages the inode table.  There are procedures to allocate and
 * deallocate inodes, acquire, erase, and release them, and read and write
 * them from the disk.
 *
 * The entry points into this file are
 *   get_inode:	   search inode table for a given inode; if not there,
 *                 read it
 *   put_inode:	   indicate that an inode is no longer needed in memory
 *   alloc_inode:  allocate a new, unused inode
 *   wipe_inode:   erase some fields of a newly allocated inode
 *   free_inode:   mark an inode as available for a new file
 *   update_times: update atime, ctime, and mtime
 *   rw_inode:	   read a disk block and extract an inode, or corresp. write
 *   old_icopy:	   copy to/from in-core inode struct and disk inode (V1.x)
 *   new_icopy:	   copy to/from in-core inode struct and disk inode (V2.x)
 *   dup_inode:	   indicate that someone else is using an inode table entry
 */

#include "fs.h"
#include "buf.h"
#include "file.h"
#include "fproc.h"
#include "inode.h"
#include "super.h"

FORWARD _PROTOTYPE( void old_icopy, (struct inode *rip, d1_inode *dip,
						int direction, int norm));
FORWARD _PROTOTYPE( void new_icopy, (struct inode *rip, d2_inode *dip,
						int direction, int norm));

/*===========================================================================*
 *				get_inode				     *
 *===========================================================================*/
PUBLIC struct inode *get_inode(dev, numb)
dev_t dev;			/* device on which inode resides */
int numb;			/* inode number (ANSI: may not be unshort) */
{
/* Find a slot in the inode table, load the specified inode into it, and
 * return a pointer to the slot.  If 'dev' == NO_DEV, just return a free slot.
 */

  register struct inode *rip, *xp;

  /* Search the inode table both for (dev, numb) and a free slot. */
  xp = NIL_INODE;
  for (rip = &inode[0]; rip < &inode[NR_INODES]; rip++) {
	if (rip->i_count > 0) { /* only check used slots for (dev, numb) */
		if (rip->i_dev == dev && rip->i_num == numb) {
			/* This is the inode that we are looking for. */
			rip->i_count++;
			return(rip);	/* (dev, numb) found */
		}
	} else {
		xp = rip;	/* remember this free slot for later */
	}
  }

  /* Inode we want is not currently in use.  Did we find a free slot? */
  if (xp == NIL_INODE) {	/* inode table completely full */
	err_code = ENFILE;
	return(NIL_INODE);
  }

  /* A free inode slot has been located.  Load the inode into it. */
  xp->i_dev = dev;
  xp->i_num = numb;
  xp->i_count = 1;
  if (dev != NO_DEV) rw_inode(xp, READING);	/* get inode from disk */
  xp->i_update = 0;		/* all the times are initially up-to-date */

  return(xp);
}

/*===========================================================================*
 *				put_inode				     *
 *===========================================================================*/
PUBLIC void put_inode(rip)
register struct inode *rip;	/* pointer to inode to be released */
{
/* The caller is no longer using this inode.  If no one else is using it either
 * write it back to the disk immediately.  If it has no links, truncate it and
 * return it to the pool of available inodes.
 */

  if (rip == NIL_INODE) return;	/* checking here is easier than in caller */
  if (--rip->i_count == 0) {	/* i_count == 0 means no one is using it now */
	if (rip->i_nlinks == 0) {
		/* i_nlinks == 0 means free the inode. */
		truncate(rip);	/* return all the disk blocks */
		rip->i_mode = I_NOT_ALLOC;	/* clear I_TYPE field */
		rip->i_dirt = DIRTY;
		free_inode(rip->i_dev, rip->i_num);
	} else {
		if (rip->i_pipe == I_PIPE) truncate(rip);
	}
	rip->i_pipe = NO_PIPE;  /* should always be cleared */
	if (rip->i_dirt == DIRTY) rw_inode(rip, WRITING);
  }
}

/*===========================================================================*
 *				alloc_inode				     *
 *===========================================================================*/
PUBLIC struct inode *alloc_inode(dev_t dev, mode_t bits)
{
/* Allocate a free inode on 'dev', and return a pointer to it. */

  register struct inode *rip;
  register struct super_block *sp;
  int major, minor, inumb;
  bit_t b;

  sp = get_super(dev);	/* get pointer to super_block */
  if (sp->s_rd_only) {	/* can't allocate an inode on a read only device. */
	err_code = EROFS;
	return(NIL_INODE);
  }

  /* Acquire an inode from the bit map. */
  b = alloc_bit(sp, IMAP, sp->s_isearch);
  if (b == NO_BIT) {
	err_code = ENFILE;
	major = (int) (sp->s_dev >> MAJOR) & BYTE;
	minor = (int) (sp->s_dev >> MINOR) & BYTE;
	printf("Out of i-nodes on %sdevice %d/%d\n",
		sp->s_dev == root_dev ? "root " : "", major, minor);
	return(NIL_INODE);
  }
  sp->s_isearch = b;		/* next time start here */
  inumb = (int) b;		/* be careful not to pass unshort as param */

  /* Try to acquire a slot in the inode table. */
  if ((rip = get_inode(NO_DEV, inumb)) == NIL_INODE) {
	/* No inode table slots available.  Free the inode just allocated. */
	free_bit(sp, IMAP, b);
  } else {
	/* An inode slot is available. Put the inode just allocated into it. */
	rip->i_mode = bits;		/* set up RWX bits */
	rip->i_nlinks = 0;		/* initial no links */
	rip->i_uid = fp->fp_effuid;	/* file's uid is owner's */
	rip->i_gid = fp->fp_effgid;	/* ditto group id */
	rip->i_dev = dev;		/* mark which device it is on */
	rip->i_ndzones = sp->s_ndzones;	/* number of direct zones */
	rip->i_nindirs = sp->s_nindirs;	/* number of indirect zones per blk*/
	rip->i_sp = sp;			/* pointer to super block */

	/* Fields not cleared already are cleared in wipe_inode().  They have
	 * been put there because truncate() needs to clear the same fields if
	 * the file happens to be open while being truncated.  It saves space
	 * not to repeat the code twice.
	 */
	wipe_inode(rip);
  }

  return(rip);
}

/*===========================================================================*
 *				wipe_inode				     *
 *===========================================================================*/
PUBLIC void wipe_inode(rip)
register struct inode *rip;	/* the inode to be erased */
{
/* Erase some fields in the inode.  This function is called from alloc_inode()
 * when a new inode is to be allocated, and from truncate(), when an existing
 * inode is to be truncated.
 */

  register int i;

  rip->i_size = 0;
  rip->i_update = ATIME | CTIME | MTIME;	/* update all times later */
  rip->i_dirt = DIRTY;
  for (i = 0; i < V2_NR_TZONES; i++) rip->i_zone[i] = NO_ZONE;
}

/*===========================================================================*
 *				free_inode				     *
 *===========================================================================*/
PUBLIC void free_inode(dev, inumb)
dev_t dev;			/* on which device is the inode */
ino_t inumb;			/* number of inode to be freed */
{
/* Return an inode to the pool of unallocated inodes. */

  register struct super_block *sp;
  bit_t b;

  /* Locate the appropriate super_block. */
  sp = get_super(dev);
  if (inumb <= 0 || inumb > sp->s_ninodes) return;
  b = inumb;
  free_bit(sp, IMAP, b);
  if (b < sp->s_isearch) sp->s_isearch = b;
}

/*===========================================================================*
 *				update_times				     *
 *===========================================================================*/
PUBLIC void update_times(rip)
register struct inode *rip;	/* pointer to inode to be read/written */
{
/* Various system calls are required by the standard to update atime, ctime,
 * or mtime.  Since updating a time requires sending a message to the clock
 * task--an expensive business--the times are marked for update by setting
 * bits in i_update.  When a stat, fstat, or sync is done, or an inode is 
 * released, update_times() may be called to actually fill in the times.
 */

  time_t cur_time;
  struct super_block *sp;

  sp = rip->i_sp;		/* get pointer to super block. */
  if (sp->s_rd_only) return;	/* no updates for read-only file systems */

  cur_time = clock_time();
  if (rip->i_update & ATIME) rip->i_atime = cur_time;
  if (rip->i_update & CTIME) rip->i_ctime = cur_time;
  if (rip->i_update & MTIME) rip->i_mtime = cur_time;
  rip->i_update = 0;		/* they are all up-to-date now */
}

/*===========================================================================*
 *				rw_inode				     *
 *===========================================================================*/
PUBLIC void rw_inode(rip, rw_flag)
register struct inode *rip;	/* pointer to inode to be read/written */
int rw_flag;			/* READING or WRITING */
{
/* An entry in the inode table is to be copied to or from the disk. */

  register struct buf *bp;
  register struct super_block *sp;
  d1_inode *dip;
  d2_inode *dip2;
  block_t b, offset;

  /* Get the block where the inode resides. */
  sp = get_super(rip->i_dev);	/* get pointer to super block */
  rip->i_sp = sp;		/* inode must contain super block pointer */
  offset = sp->s_imap_blocks + sp->s_zmap_blocks + 2;
  b = (block_t) (rip->i_num - 1)/sp->s_inodes_per_block + offset;
  bp = get_block(rip->i_dev, b, NORMAL);
  dip  = bp->b_v1_ino + (rip->i_num - 1) % V1_INODES_PER_BLOCK;
  dip2 = bp->b_v2_ino + (rip->i_num - 1) %
  	 V2_INODES_PER_BLOCK(sp->s_block_size);

  /* Do the read or write. */
  if (rw_flag == WRITING) {
	if (rip->i_update) update_times(rip);	/* times need updating */
	if (sp->s_rd_only == FALSE) bp->b_dirt = DIRTY;
  }

  /* Copy the inode from the disk block to the in-core table or vice versa.
   * If the fourth parameter below is FALSE, the bytes are swapped.
   */
  if (sp->s_version == V1)
	old_icopy(rip, dip,  rw_flag, sp->s_native);
  else
	new_icopy(rip, dip2, rw_flag, sp->s_native);
  
  put_block(bp, INODE_BLOCK);
  rip->i_dirt = CLEAN;
}

/*===========================================================================*
 *				old_icopy				     *
 *===========================================================================*/
PRIVATE void old_icopy(rip, dip, direction, norm)
register struct inode *rip;	/* pointer to the in-core inode struct */
register d1_inode *dip;		/* pointer to the d1_inode inode struct */
int direction;			/* READING (from disk) or WRITING (to disk) */
int norm;			/* TRUE = do not swap bytes; FALSE = swap */

{
/* The V1.x IBM disk, the V1.x 68000 disk, and the V2 disk (same for IBM and
 * 68000) all have different inode layouts.  When an inode is read or written
 * this routine handles the conversions so that the information in the inode
 * table is independent of the disk structure from which the inode came.
 * The old_icopy routine copies to and from V1 disks.
 */

  int i;

  if (direction == READING) {
	/* Copy V1.x inode to the in-core table, swapping bytes if need be. */
	rip->i_mode    = conv2(norm, (int) dip->d1_mode);
	rip->i_uid     = conv2(norm, (int) dip->d1_uid );
	rip->i_size    = conv4(norm,       dip->d1_size);
	rip->i_mtime   = conv4(norm,       dip->d1_mtime);
	rip->i_atime   = rip->i_mtime;
	rip->i_ctime   = rip->i_mtime;
	rip->i_nlinks  = dip->d1_nlinks;		/* 1 char */
	rip->i_gid     = dip->d1_gid;			/* 1 char */
	rip->i_ndzones = V1_NR_DZONES;
	rip->i_nindirs = V1_INDIRECTS;
	for (i = 0; i < V1_NR_TZONES; i++)
		rip->i_zone[i] = conv2(norm, (int) dip->d1_zone[i]);
  } else {
	/* Copying V1.x inode to disk from the in-core table. */
	dip->d1_mode   = conv2(norm, (int) rip->i_mode);
	dip->d1_uid    = conv2(norm, (int) rip->i_uid );
	dip->d1_size   = conv4(norm,       rip->i_size);
	dip->d1_mtime  = conv4(norm,       rip->i_mtime);
	dip->d1_nlinks = rip->i_nlinks;			/* 1 char */
	dip->d1_gid    = rip->i_gid;			/* 1 char */
	for (i = 0; i < V1_NR_TZONES; i++)
		dip->d1_zone[i] = conv2(norm, (int) rip->i_zone[i]);
  }
}

/*===========================================================================*
 *				new_icopy				     *
 *===========================================================================*/
PRIVATE void new_icopy(rip, dip, direction, norm)
register struct inode *rip;	/* pointer to the in-core inode struct */
register d2_inode *dip;	/* pointer to the d2_inode struct */
int direction;			/* READING (from disk) or WRITING (to disk) */
int norm;			/* TRUE = do not swap bytes; FALSE = swap */

{
/* Same as old_icopy, but to/from V2 disk layout. */

  int i;

  if (direction == READING) {
	/* Copy V2.x inode to the in-core table, swapping bytes if need be. */
	rip->i_mode    = conv2(norm,dip->d2_mode);
	rip->i_uid     = conv2(norm,dip->d2_uid);
	rip->i_nlinks  = conv2(norm,dip->d2_nlinks);
	rip->i_gid     = conv2(norm,dip->d2_gid);
	rip->i_size    = conv4(norm,dip->d2_size);
	rip->i_atime   = conv4(norm,dip->d2_atime);
	rip->i_ctime   = conv4(norm,dip->d2_ctime);
	rip->i_mtime   = conv4(norm,dip->d2_mtime);
	rip->i_ndzones = V2_NR_DZONES;
	rip->i_nindirs = V2_INDIRECTS(rip->i_sp->s_block_size);
	for (i = 0; i < V2_NR_TZONES; i++)
		rip->i_zone[i] = conv4(norm, (long) dip->d2_zone[i]);
  } else {
	/* Copying V2.x inode to disk from the in-core table. */
	dip->d2_mode   = conv2(norm,rip->i_mode);
	dip->d2_uid    = conv2(norm,rip->i_uid);
	dip->d2_nlinks = conv2(norm,rip->i_nlinks);
	dip->d2_gid    = conv2(norm,rip->i_gid);
	dip->d2_size   = conv4(norm,rip->i_size);
	dip->d2_atime  = conv4(norm,rip->i_atime);
	dip->d2_ctime  = conv4(norm,rip->i_ctime);
	dip->d2_mtime  = conv4(norm,rip->i_mtime);
	for (i = 0; i < V2_NR_TZONES; i++)
		dip->d2_zone[i] = conv4(norm, (long) rip->i_zone[i]);
  }
}

/*===========================================================================*
 *				dup_inode				     *
 *===========================================================================*/
PUBLIC void dup_inode(ip)
struct inode *ip;		/* The inode to be duplicated. */
{
/* This routine is a simplified form of get_inode() for the case where
 * the inode pointer is already known.
 */

  ip->i_count++;
}