lib/ext2fs/symlink.c

   1 /*
   2  * symlink.c --- make a symlink in the filesystem, based on mkdir.c
   3  *
   4  * Copyright (c) 2012, Intel Corporation.
   5  * All Rights Reserved.
   6  *
   7  * %Begin-Header%
   8  * This file may be redistributed under the terms of the GNU Library
   9  * General Public License, version 2.
  10  * %End-Header%
  11  */
  12
  13 #include "config.h"
  14 #include <stdio.h>
  15 #include <string.h>
  16 #if HAVE_UNISTD_H
  17 #include <unistd.h>
  18 #endif
  19 #include <fcntl.h>
  20 #include <time.h>
  21 #if HAVE_SYS_STAT_H
  22 #include <sys/stat.h>
  23 #endif
  24 #if HAVE_SYS_TYPES_H
  25 #include <sys/types.h>
  26 #endif
  27
  28 #include "ext2_fs.h"
  29 #include "ext2fs.h"
  30
  31 errcode_t ext2fs_symlink(ext2_filsys fs, ext2_ino_t parent, ext2_ino_t ino,
  32                          const char *name, char *target)
  33 {
  34         errcode_t               retval;
  35         struct ext2_inode       inode;
  36         ext2_ino_t              scratch_ino;
  37         blk64_t                 blk;
  38         int                     fastlink;
  39         unsigned int            target_len;
  40         char                    *block_buf = 0;
  41
  42         EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);
  43
  44         /* The Linux kernel doesn't allow for links longer than a block */
  45         target_len = strlen(target);
  46         if (target_len > fs->blocksize) {
  47                 retval = EXT2_ET_INVALID_ARGUMENT;
  48                 goto cleanup;
  49         }
  50
  51         /*
  52          * Allocate a data block for slow links
  53          */
  54         fastlink = (target_len < sizeof(inode.i_block));
  55         if (!fastlink) {
  56                 retval = ext2fs_new_block2(fs, 0, 0, &blk);
  57                 if (retval)
  58                         goto cleanup;
  59                 retval = ext2fs_get_mem(fs->blocksize, &block_buf);
  60                 if (retval)
  61                         goto cleanup;
  62         }
  63
  64         /*
  65          * Allocate an inode, if necessary
  66          */
  67         if (!ino) {
  68                 retval = ext2fs_new_inode(fs, parent, LINUX_S_IFLNK | 0755,
  69                                           0, &ino);
  70                 if (retval)
  71                         goto cleanup;
  72         }
  73
  74         /*
  75          * Create the inode structure....
  76          */
  77         memset(&inode, 0, sizeof(struct ext2_inode));
  78         inode.i_mode = LINUX_S_IFLNK | 0777;
  79         inode.i_uid = inode.i_gid = 0;
  80         ext2fs_iblk_set(fs, &inode, fastlink ? 0 : 1);
  81         inode.i_links_count = 1;
  82         ext2fs_inode_size_set(fs, &inode, target_len);
  83         /* The time fields are set by ext2fs_write_new_inode() */
  84
  85         if (fastlink) {
  86                 /* Fast symlinks, target stored in inode */
  87                 strcpy((char *)&inode.i_block, target);
  88         } else {
  89                 /* Slow symlinks, target stored in the first block */
  90                 memset(block_buf, 0, fs->blocksize);
  91                 strncpy(block_buf, target, fs->blocksize);
  92                 if (fs->super->s_feature_incompat &
  93                     EXT3_FEATURE_INCOMPAT_EXTENTS) {
  94                         /*
  95                          * The extent bmap is setup after the inode and block
  96                          * have been written out below.
  97                          */
  98                         inode.i_flags |= EXT4_EXTENTS_FL;
  99                 }
 100         }
 101
 102         /*
 103          * Write out the inode and inode data block.  The inode generation
 104          * number is assigned by write_new_inode, which means that the
 105          * operations using ino must come after it.
 106          */
 107         retval = ext2fs_write_new_inode(fs, ino, &inode);
 108         if (retval)
 109                 goto cleanup;
 110
 111         if (!fastlink) {
 112                 retval = ext2fs_bmap2(fs, ino, &inode, NULL, BMAP_SET, 0, NULL,
 113                                       &blk);
 114                 if (retval)
 115                         goto cleanup;
 116
 117                 retval = io_channel_write_blk64(fs->io, blk, 1, block_buf);
 118                 if (retval)
 119                         goto cleanup;
 120         }
 121
 122         /*
 123          * Link the symlink into the filesystem hierarchy
 124          */
 125         if (name) {
 126                 retval = ext2fs_lookup(fs, parent, name, strlen(name), 0,
 127                                        &scratch_ino);
 128                 if (!retval) {
 129                         retval = EXT2_ET_FILE_EXISTS;
 130                         goto cleanup;
 131                 }
 132                 if (retval != EXT2_ET_FILE_NOT_FOUND)
 133                         goto cleanup;
 134                 retval = ext2fs_link(fs, parent, name, ino, EXT2_FT_SYMLINK);
 135                 if (retval)
 136                         goto cleanup;
 137         }
 138
 139         /*
 140          * Update accounting....
 141          */
 142         if (!fastlink)
 143                 ext2fs_block_alloc_stats2(fs, blk, +1);
 144         ext2fs_inode_alloc_stats2(fs, ino, +1, 0);
 145
 146 cleanup:
 147         if (block_buf)
 148                 ext2fs_free_mem(&block_buf);
 149         return retval;
 150 }