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Sourcecode: unionfs-fuse version File versions  Download package

unlink.c

/*
*  C Implementation: unlink
*
* Description: unionfs unlink() call
*              If the file to unlink exists in a lower branch, create a
*              file with a tag informing other functions that the file
*              is hidden.
*
* original implementation by Radek Podgorny
*
* License: BSD-style license
* Copyright: Radek Podgorny <radek@podgorny.cz>,
*            Bernd Schubert <bernd-schubert@gmx.de>
*
*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <unistd.h>
#include <errno.h>
#include <libgen.h>

#include "unionfs.h"
#include "opts.h"
#include "debug.h"
#include "cow.h"
#include "general.h"
#include "findbranch.h"

/**
  * If the branch that has the file to be unlinked is in read-only mode,
  * we create a file with a HIDE tag in an upper level branch.
  * To other fuse functions this tag means, not to expose the 
  * lower level file.
  */
static int unlink_ro(const char *path, int branch_ro) {
      DBG_IN()    

      // find a writable branch above branch_ro
      int branch_rw = find_lowest_rw_branch(branch_ro);

      if (branch_rw < 0) return EACCES;

      if (hide_file(path, branch_rw) == -1) {
            // creating the file with the hide tag failed
            // TODO: open() error messages are not optimal on unlink()
            return errno;
      }

      return 0;
}

/**
  * If the branch that has the file to be unlinked is in read-write mode,
  * we can really delete the file.
  */
static int unlink_rw(const char *path, int branch_rw) {
      DBG_IN();
      
      char p[PATHLEN_MAX];
      snprintf(p, PATHLEN_MAX, "%s%s", uopt.branches[branch_rw].path, path);

      int res = unlink(p);
      if (res == -1) return errno;

      return 0;
}

/**
  * unlink() call
  */
int unionfs_unlink(const char *path) {
      DBG_IN();
      
      int i = find_rorw_branch(path);
      if (i == -1) return errno;

      int res;
      if (!uopt.branches[i].rw) {
            // read-only branch
            if (!uopt.cow_enabled) {
                  res = EROFS;
            } else {
                  res = unlink_ro(path, i);
            }
      } else {
            // read-write branch
            res = unlink_rw(path, i);
            if (res == 0) {
                  // No need to be root, whiteouts are created as root!
                  maybe_whiteout(path, i, WHITEOUT_FILE);
            }
      }

      return -res;
}

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