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         ext2_extent_handle_t    handle;
  35         errcode_t               retval;
  36         struct ext2_inode       inode;
  37         ext2_ino_t              scratch_ino;
  38         blk64_t                 blk;
  39         int                     fastlink;
  40         unsigned int            target_len;
  41         char                    *block_buf = 0;
  42
  43         EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);
  44
  45         /* The Linux kernel doesn't allow for links longer than a block */
  46         target_len = strlen(target);
  47         if (target_len > fs->blocksize) {
  48                 retval = EXT2_ET_INVALID_ARGUMENT;
  49                 goto cleanup;
  50         }
  51
  52         /*
  53          * Allocate a data block for slow links
  54          */
  55         fastlink = (target_len < sizeof(inode.i_block));
  56         if (!fastlink) {
  57                 retval = ext2fs_new_block2(fs, 0, 0, &blk);
  58                 if (retval)
  59                         goto cleanup;
  60                 retval = ext2fs_get_mem(fs->blocksize, &block_buf);
  61                 if (retval)
  62                         goto cleanup;
  63         }
  64
  65         /*
  66          * Allocate an inode, if necessary
  67          */
  68         if (!ino) {
  69                 retval = ext2fs_new_inode(fs, parent, LINUX_S_IFLNK | 0755,
  70                                           0, &ino);
  71                 if (retval)
  72                         goto cleanup;
  73         }
  74
  75         /*
  76          * Create the inode structure....
  77          */
  78         memset(&inode, 0, sizeof(struct ext2_inode));
  79         inode.i_mode = LINUX_S_IFLNK | 0777;
  80         inode.i_uid = inode.i_gid = 0;
  81         ext2fs_iblk_set(fs, &inode, fastlink ? 0 : 1);
  82         inode.i_links_count = 1;
  83         inode.i_size = target_len;
  84         /* The time fields are set by ext2fs_write_new_inode() */
  85
  86         if (fastlink) {
  87                 /* Fast symlinks, target stored in inode */
  88                 strcpy((char *)&inode.i_block, target);
  89         } else {
  90                 /* Slow symlinks, target stored in the first block */
  91                 memset(block_buf, 0, fs->blocksize);
  92                 strcpy(block_buf, target);
  93                 if (fs->super->s_feature_incompat &
  94                     EXT3_FEATURE_INCOMPAT_EXTENTS) {
  95                         /*
  96                          * The extent bmap is setup after the inode and block
  97                          * have been written out below.
  98                          */
  99                         inode.i_flags |= EXT4_EXTENTS_FL;
 100                 }
 101         }
 102
 103         /*
 104          * Write out the inode and inode data block.  The inode generation
 105          * number is assigned by write_new_inode, which means that the
 106          * operations using ino must come after it.
 107          */
 108         retval = ext2fs_write_new_inode(fs, ino, &inode);
 109         if (retval)
 110                 goto cleanup;
 111
 112         if (!fastlink) {
 113                 retval = ext2fs_bmap2(fs, ino, &inode, NULL, BMAP_SET, 0, NULL,
 114                                       &blk);
 115                 if (retval)
 116                         goto cleanup;
 117
 118                 retval = io_channel_write_blk64(fs->io, blk, 1, block_buf);
 119                 if (retval)
 120                         goto cleanup;
 121         }
 122
 123         /*
 124          * Link the symlink into the filesystem hierarchy
 125          */
 126         if (name) {
 127                 retval = ext2fs_lookup(fs, parent, name, strlen(name), 0,
 128                                        &scratch_ino);
 129                 if (!retval) {
 130                         retval = EXT2_ET_FILE_EXISTS;
 131                         goto cleanup;
 132                 }
 133                 if (retval != EXT2_ET_FILE_NOT_FOUND)
 134                         goto cleanup;
 135                 retval = ext2fs_link(fs, parent, name, ino, EXT2_FT_SYMLINK);
 136                 if (retval)
 137                         goto cleanup;
 138         }
 139
 140         /*
 141          * Update accounting....
 142          */
 143         if (!fastlink)
 144                 ext2fs_block_alloc_stats2(fs, blk, +1);
 145         ext2fs_inode_alloc_stats2(fs, ino, +1, 0);
 146
 147 cleanup:
 148         if (block_buf)
 149                 ext2fs_free_mem(&block_buf);
 150         return retval;
 151 }