servers/mfs/open.c
#include "fs.h"
#include <sys/stat.h>
#include <string.h>
#include <minix/com.h>
#include "buf.h"
#include "inode.h"
#include "super.h"
#include <minix/vfsif.h>

static struct inode *new_node(struct inode *ldirp, char *string, mode_t
	bits, zone_t z0);

/*===========================================================================*
 *				fs_create				     *
 *===========================================================================*/
int fs_create()
{
  size_t len;
  int r;
  struct inode *ldirp;
  struct inode *rip;
  mode_t omode;
  char lastc[MFS_NAME_MAX];
  
  /* Read request message */
  omode = (mode_t) fs_m_in.REQ_MODE;
  caller_uid = (uid_t) fs_m_in.REQ_UID;
  caller_gid = (gid_t) fs_m_in.REQ_GID;
  
  /* Try to make the file. */ 

  /* Copy the last component (i.e., file name) */
  len = min( (unsigned) fs_m_in.REQ_PATH_LEN, sizeof(lastc));
  err_code = sys_safecopyfrom(VFS_PROC_NR, (cp_grant_id_t) fs_m_in.REQ_GRANT,
			      (vir_bytes) 0, (vir_bytes) lastc, len);
  if (err_code != OK) return err_code;
  NUL(lastc, len, sizeof(lastc));

  /* Get last directory inode (i.e., directory that will hold the new inode) */
  if ((ldirp = get_inode(fs_dev, (ino_t) fs_m_in.REQ_INODE_NR)) == NULL)
	  return(ENOENT);

  /* Create a new inode by calling new_node(). */
  rip = new_node(ldirp, lastc, omode, NO_ZONE);
  r = err_code;

  /* If an error occurred, release inode. */
  if (r != OK) {
	  put_inode(ldirp);
	  put_inode(rip);
	  return(r);
  }
  
  /* Reply message */
  fs_m_out.RES_INODE_NR = rip->i_num;
  fs_m_out.RES_MODE = rip->i_mode;
  fs_m_out.RES_FILE_SIZE_LO = rip->i_size;

  /* These values are needed for the execution */
  fs_m_out.RES_UID = rip->i_uid;
  fs_m_out.RES_GID = rip->i_gid;

  /* Drop parent dir */
  put_inode(ldirp);
  
  return(OK);
}


/*===========================================================================*
 *				fs_mknod				     *
 *===========================================================================*/
int fs_mknod()
{
  struct inode *ip, *ldirp;
  char lastc[MFS_NAME_MAX];
  phys_bytes len;

  /* Copy the last component and set up caller's user and group id */
  len = min( (unsigned) fs_m_in.REQ_PATH_LEN, sizeof(lastc));
  err_code = sys_safecopyfrom(VFS_PROC_NR, (cp_grant_id_t) fs_m_in.REQ_GRANT,
  			    (vir_bytes) 0, (vir_bytes) lastc, (size_t) len);
  if (err_code != OK) return err_code;
  NUL(lastc, len, sizeof(lastc));
  
  caller_uid = (uid_t) fs_m_in.REQ_UID;
  caller_gid = (gid_t) fs_m_in.REQ_GID;
  
  /* Get last directory inode */
  if((ldirp = get_inode(fs_dev, (ino_t) fs_m_in.REQ_INODE_NR)) == NULL)
	  return(ENOENT);

  /* Try to create the new node */
  ip = new_node(ldirp, lastc, (mode_t) fs_m_in.REQ_MODE,
  		(zone_t) fs_m_in.REQ_DEV);

  put_inode(ip);
  put_inode(ldirp);
  return(err_code);
}


/*===========================================================================*
 *				fs_mkdir				     *
 *===========================================================================*/
int fs_mkdir()
{
  int r1, r2;			/* status codes */
  ino_t dot, dotdot;		/* inode numbers for . and .. */
  struct inode *rip, *ldirp;
  char lastc[MFS_NAME_MAX];         /* last component */
  phys_bytes len;

  /* Copy the last component and set up caller's user and group id */
  len = min( (unsigned) fs_m_in.REQ_PATH_LEN, sizeof(lastc));
  err_code = sys_safecopyfrom(VFS_PROC_NR, (cp_grant_id_t) fs_m_in.REQ_GRANT,
  			   (vir_bytes) 0, (vir_bytes) lastc, (size_t) len);
  if(err_code != OK) return(err_code);
  NUL(lastc, len, sizeof(lastc));

  caller_uid = (uid_t) fs_m_in.REQ_UID;
  caller_gid = (gid_t) fs_m_in.REQ_GID;
  
  /* Get last directory inode */
  if((ldirp = get_inode(fs_dev, (ino_t) fs_m_in.REQ_INODE_NR)) == NULL)
      return(ENOENT);
  
  /* Next make the inode. If that fails, return error code. */
  rip = new_node(ldirp, lastc, (mode_t) fs_m_in.REQ_MODE, (zone_t) 0);
  
  if(rip == NULL || err_code == EEXIST) {
	  put_inode(rip);		/* can't make dir: it already exists */
	  put_inode(ldirp);
	  return(err_code);
  }
  
  /* Get the inode numbers for . and .. to enter in the directory. */
  dotdot = ldirp->i_num;	/* parent's inode number */
  dot = rip->i_num;		/* inode number of the new dir itself */

  /* Now make dir entries for . and .. unless the disk is completely full. */
  /* Use dot1 and dot2, so the mode of the directory isn't important. */
  rip->i_mode = (mode_t) fs_m_in.REQ_MODE;	/* set mode */
  r1 = search_dir(rip, dot1, &dot, ENTER, IGN_PERM);/* enter . in the new dir*/
  r2 = search_dir(rip, dot2, &dotdot, ENTER, IGN_PERM); /* enter .. in the new
							 dir */

  /* If both . and .. were successfully entered, increment the link counts. */
  if (r1 == OK && r2 == OK) {
	  /* Normal case.  It was possible to enter . and .. in the new dir. */
	  rip->i_nlinks++;	/* this accounts for . */
	  ldirp->i_nlinks++;	/* this accounts for .. */
	  IN_MARKDIRTY(ldirp);	/* mark parent's inode as dirty */
  } else {
	  /* It was not possible to enter . or .. probably disk was full -
	   * links counts haven't been touched. */
	  if(search_dir(ldirp, lastc, NULL, DELETE, IGN_PERM) != OK)
		  panic("Dir disappeared: %ul", rip->i_num);
	  rip->i_nlinks--;	/* undo the increment done in new_node() */
  }
  IN_MARKDIRTY(rip);		/* either way, i_nlinks has changed */

  put_inode(ldirp);		/* return the inode of the parent dir */
  put_inode(rip);		/* return the inode of the newly made dir */
  return(err_code);		/* new_node() always sets 'err_code' */
}


/*===========================================================================*
 *                             fs_slink 				     *
 *===========================================================================*/
int fs_slink()
{
  phys_bytes len;
  struct inode *sip;           /* inode containing symbolic link */
  struct inode *ldirp;         /* directory containing link */
  register int r;              /* error code */
  char string[MFS_NAME_MAX];       /* last component of the new dir's path name */
  struct buf *bp;              /* disk buffer for link */
    
  caller_uid = (uid_t) fs_m_in.REQ_UID;
  caller_gid = (gid_t) fs_m_in.REQ_GID;
  
  /* Copy the link name's last component */
  len = min( (unsigned) fs_m_in.REQ_PATH_LEN, sizeof(string));
  r = sys_safecopyfrom(VFS_PROC_NR, (cp_grant_id_t) fs_m_in.REQ_GRANT,
  			(vir_bytes) 0, (vir_bytes) string, (size_t) len);
  if (r != OK) return(r);
  NUL(string, len, sizeof(string));
  
  /* Temporarily open the dir. */
  if( (ldirp = get_inode(fs_dev, (ino_t) fs_m_in.REQ_INODE_NR)) == NULL)
	  return(EINVAL);

  /* Create the inode for the symlink. */
  sip = new_node(ldirp, string, (mode_t) (I_SYMBOLIC_LINK | RWX_MODES),
		   (zone_t) 0);

  /* Allocate a disk block for the contents of the symlink.
   * Copy contents of symlink (the name pointed to) into first disk block. */
  if( (r = err_code) == OK) {
  	bp = new_block(sip, (off_t) 0);
  	if (bp == NULL)
  		r = err_code;
  	else
  		r = sys_safecopyfrom(VFS_PROC_NR,
  				     (cp_grant_id_t) fs_m_in.REQ_GRANT3,
				     (vir_bytes) 0, (vir_bytes) b_data(bp),
				     (size_t) fs_m_in.REQ_MEM_SIZE);

	if(bp != NULL && r == OK) {
		b_data(bp)[_MIN_BLOCK_SIZE-1] = '\0';
		sip->i_size = (off_t) strlen(b_data(bp));
		if(sip->i_size != fs_m_in.REQ_MEM_SIZE) {
			/* This can happen if the user provides a buffer
			 * with a \0 in it. This can cause a lot of trouble
			 * when the symlink is used later. We could just use
			 * the strlen() value, but we want to let the user
			 * know he did something wrong. ENAMETOOLONG doesn't
			 * exactly describe the error, but there is no
			 * ENAMETOOWRONG.
			 */
			r = ENAMETOOLONG;
		}
	}
	  
	put_block(bp, DIRECTORY_BLOCK); /* put_block() accepts NULL. */
  
	if(r != OK) {
		sip->i_nlinks = NO_LINK;
		if(search_dir(ldirp, string, NULL, DELETE, IGN_PERM) != OK)
			  panic("Symbolic link vanished");
	} 
  }

  /* put_inode() accepts NULL as a noop, so the below are safe. */
  put_inode(sip);
  put_inode(ldirp);
  
  return(r);
}

/*===========================================================================*
 *				new_node				     *
 *===========================================================================*/
static struct inode *new_node(struct inode *ldirp,
	char *string, mode_t bits, zone_t z0)
{
/* New_node() is called by fs_open(), fs_mknod(), and fs_mkdir().  
 * In all cases it allocates a new inode, makes a directory entry for it in
 * the ldirp directory with string name, and initializes it.  
 * It returns a pointer to the inode if it can do this; 
 * otherwise it returns NULL.  It always sets 'err_code'
 * to an appropriate value (OK or an error code).
 * 
 * The parsed path rest is returned in 'parsed' if parsed is nonzero. It
 * has to hold at least MFS_NAME_MAX bytes.
 */

  register struct inode *rip;
  register int r;

  if (ldirp->i_nlinks == NO_LINK) {	/* Dir does not actually exist */
  	err_code = ENOENT;
  	return(NULL);
  }

  /* Get final component of the path. */
  rip = advance(ldirp, string, IGN_PERM);

  if (S_ISDIR(bits) && (ldirp->i_nlinks >= LINK_MAX)) {
        /* New entry is a directory, alas we can't give it a ".." */
        put_inode(rip);
        err_code = EMLINK;
        return(NULL);
  }

  if ( rip == NULL && err_code == ENOENT) {
	/* Last path component does not exist.  Make new directory entry. */
	if ( (rip = alloc_inode((ldirp)->i_dev, bits)) == NULL) {
		/* Can't creat new inode: out of inodes. */
		return(NULL);
	}

	/* Force inode to the disk before making directory entry to make
	 * the system more robust in the face of a crash: an inode with
	 * no directory entry is much better than the opposite.
	 */
	rip->i_nlinks++;
	rip->i_zone[0] = z0;		/* major/minor device numbers */
	rw_inode(rip, WRITING);		/* force inode to disk now */

	/* New inode acquired.  Try to make directory entry. */
	if((r=search_dir(ldirp, string, &rip->i_num, ENTER, IGN_PERM)) != OK) {
		rip->i_nlinks--;	/* pity, have to free disk inode */
		IN_MARKDIRTY(rip);	/* dirty inodes are written out */
		put_inode(rip);	/* this call frees the inode */
		err_code = r;
		return(NULL);
	}

  } else if (err_code == EENTERMOUNT || err_code == ELEAVEMOUNT) {
  	r = EEXIST;
  } else { 
	/* Either last component exists, or there is some problem. */
	if (rip != NULL)
		r = EEXIST;
	else
		r = err_code;
  }

  /* The caller has to return the directory inode (*ldirp).  */
  err_code = r;
  return(rip);
}


/*===========================================================================*
 *				fs_inhibread				     *
 *===========================================================================*/
int fs_inhibread()
{
  struct inode *rip;
  
  if((rip = find_inode(fs_dev, (ino_t) fs_m_in.REQ_INODE_NR)) == NULL)
	  return(EINVAL);

  /* inhibit read ahead */
  rip->i_seek = ISEEK;	
  
  return(OK);
}

