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/*
* 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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