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, inlinelink;
  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         memset(&inode, 0, sizeof(struct ext2_inode));
  55         fastlink = (target_len < sizeof(inode.i_block));
  56         if (!fastlink) {
  57                 retval = ext2fs_new_block2(fs, ext2fs_find_inode_goal(fs, ino,
  58                                                                       &inode,
  59                                                                       0),
  60                                            NULL, &blk);
  61                 if (retval)
  62                         goto cleanup;
  63                 retval = ext2fs_get_mem(fs->blocksize, &block_buf);
  64                 if (retval)
  65                         goto cleanup;
  66         }
  67
  68         /*
  69          * Allocate an inode, if necessary
  70          */
  71         if (!ino) {
  72                 retval = ext2fs_new_inode(fs, parent, LINUX_S_IFLNK | 0755,
  73                                           0, &ino);
  74                 if (retval)
  75                         goto cleanup;
  76         }
  77
  78         /*
  79          * Create the inode structure....
  80          */
  81         inode.i_mode = LINUX_S_IFLNK | 0777;
  82         inode.i_uid = inode.i_gid = 0;
  83         inode.i_links_count = 1;
  84         ext2fs_inode_size_set(fs, &inode, target_len);
  85         /* The time fields are set by ext2fs_write_new_inode() */
  86
  87         inlinelink = !fastlink &&
  88                      (fs->super->s_feature_incompat &
  89                                         EXT4_FEATURE_INCOMPAT_INLINE_DATA) &&
  90                      (target_len < fs->blocksize);
  91         if (fastlink) {
  92                 /* Fast symlinks, target stored in inode */
  93                 strcpy((char *)&inode.i_block, target);
  94         } else if (inlinelink) {
  95                 /* Try inserting an inline data symlink */
  96                 inode.i_flags |= EXT4_INLINE_DATA_FL;
  97                 retval = ext2fs_write_new_inode(fs, ino, &inode);
  98                 if (retval)
  99                         goto cleanup;
 100                 retval = ext2fs_inline_data_set(fs, ino, &inode, target,
 101                                                 target_len);
 102                 if (retval) {
 103                         inode.i_flags &= ~EXT4_INLINE_DATA_FL;
 104                         inlinelink = 0;
 105                         goto need_block;
 106                 }
 107                 retval = ext2fs_read_inode(fs, ino, &inode);
 108                 if (retval)
 109                         goto cleanup;
 110         } else {
 111 need_block:
 112                 ext2fs_iblk_set(fs, &inode, 1);
 113                 /* Slow symlinks, target stored in the first block */
 114                 memset(block_buf, 0, fs->blocksize);
 115                 strncpy(block_buf, target, fs->blocksize);
 116                 if (fs->super->s_feature_incompat &
 117                     EXT3_FEATURE_INCOMPAT_EXTENTS) {
 118                         /*
 119                          * The extent bmap is setup after the inode and block
 120                          * have been written out below.
 121                          */
 122                         inode.i_flags |= EXT4_EXTENTS_FL;
 123                 }
 124         }
 125
 126         /*
 127          * Write out the inode and inode data block.  The inode generation
 128          * number is assigned by write_new_inode, which means that the
 129          * operations using ino must come after it.
 130          */
 131         if (inlinelink)
 132                 retval = ext2fs_write_inode(fs, ino, &inode);
 133         else
 134                 retval = ext2fs_write_new_inode(fs, ino, &inode);
 135         if (retval)
 136                 goto cleanup;
 137
 138         if (!fastlink && !inlinelink) {
 139                 retval = ext2fs_bmap2(fs, ino, &inode, NULL, BMAP_SET, 0, NULL,
 140                                       &blk);
 141                 if (retval)
 142                         goto cleanup;
 143
 144                 retval = io_channel_write_blk64(fs->io, blk, 1, block_buf);
 145                 if (retval)
 146                         goto cleanup;
 147         }
 148
 149         /*
 150          * Link the symlink into the filesystem hierarchy
 151          */
 152         if (name) {
 153                 retval = ext2fs_lookup(fs, parent, name, strlen(name), 0,
 154                                        &scratch_ino);
 155                 if (!retval) {
 156                         retval = EXT2_ET_FILE_EXISTS;
 157                         goto cleanup;
 158                 }
 159                 if (retval != EXT2_ET_FILE_NOT_FOUND)
 160                         goto cleanup;
 161                 retval = ext2fs_link(fs, parent, name, ino, EXT2_FT_SYMLINK);
 162                 if (retval)
 163                         goto cleanup;
 164         }
 165
 166         /*
 167          * Update accounting....
 168          */
 169         if (!fastlink && !inlinelink)
 170                 ext2fs_block_alloc_stats2(fs, blk, +1);
 171         ext2fs_inode_alloc_stats2(fs, ino, +1, 0);
 172
 173 cleanup:
 174         if (block_buf)
 175                 ext2fs_free_mem(&block_buf);
 176         return retval;
 177 }