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, const 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 = strnlen(target, fs->blocksize + 1);
  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         retval = ext2fs_get_mem(fs->blocksize+1, &block_buf);
  55         if (retval)
  56                 goto cleanup;
  57         memset(block_buf, 0, fs->blocksize+1);
  58         strncpy(block_buf, target, fs->blocksize);
  59
  60         memset(&inode, 0, sizeof(struct ext2_inode));
  61         fastlink = (target_len < sizeof(inode.i_block));
  62         if (!fastlink) {
  63                 retval = ext2fs_new_block2(fs, ext2fs_find_inode_goal(fs, ino,
  64                                                                       &inode,
  65                                                                       0),
  66                                            NULL, &blk);
  67                 if (retval)
  68                         goto cleanup;
  69         }
  70
  71         /*
  72          * Allocate an inode, if necessary
  73          */
  74         if (!ino) {
  75                 retval = ext2fs_new_inode(fs, parent, LINUX_S_IFLNK | 0755,
  76                                           0, &ino);
  77                 if (retval)
  78                         goto cleanup;
  79         }
  80
  81         /*
  82          * Create the inode structure....
  83          */
  84         inode.i_mode = LINUX_S_IFLNK | 0777;
  85         inode.i_uid = inode.i_gid = 0;
  86         inode.i_links_count = 1;
  87         ext2fs_inode_size_set(fs, &inode, target_len);
  88         /* The time fields are set by ext2fs_write_new_inode() */
  89
  90         inlinelink = !fastlink &&
  91                      (fs->super->s_feature_incompat &
  92                                         EXT4_FEATURE_INCOMPAT_INLINE_DATA) &&
  93                      (target_len < fs->blocksize);
  94         if (fastlink) {
  95                 /* Fast symlinks, target stored in inode */
  96                 strcpy((char *)&inode.i_block, target);
  97         } else if (inlinelink) {
  98                 /* Try inserting an inline data symlink */
  99                 inode.i_flags |= EXT4_INLINE_DATA_FL;
 100                 retval = ext2fs_write_new_inode(fs, ino, &inode);
 101                 if (retval)
 102                         goto cleanup;
 103                 retval = ext2fs_inline_data_set(fs, ino, &inode, block_buf,
 104                                                 target_len);
 105                 if (retval) {
 106                         inode.i_flags &= ~EXT4_INLINE_DATA_FL;
 107                         inlinelink = 0;
 108                         goto need_block;
 109                 }
 110                 retval = ext2fs_read_inode(fs, ino, &inode);
 111                 if (retval)
 112                         goto cleanup;
 113         } else {
 114 need_block:
 115                 /* Slow symlinks, target stored in the first block */
 116                 ext2fs_iblk_set(fs, &inode, 1);
 117                 if (fs->super->s_feature_incompat &
 118                     EXT3_FEATURE_INCOMPAT_EXTENTS) {
 119                         /*
 120                          * The extent bmap is setup after the inode and block
 121                          * have been written out below.
 122                          */
 123                         inode.i_flags |= EXT4_EXTENTS_FL;
 124                 }
 125         }
 126
 127         /*
 128          * Write out the inode and inode data block.  The inode generation
 129          * number is assigned by write_new_inode, which means that the
 130          * operations using ino must come after it.
 131          */
 132         if (inlinelink)
 133                 retval = ext2fs_write_inode(fs, ino, &inode);
 134         else
 135                 retval = ext2fs_write_new_inode(fs, ino, &inode);
 136         if (retval)
 137                 goto cleanup;
 138
 139         if (!fastlink && !inlinelink) {
 140                 retval = ext2fs_bmap2(fs, ino, &inode, NULL, BMAP_SET, 0, NULL,
 141                                       &blk);
 142                 if (retval)
 143                         goto cleanup;
 144
 145                 retval = io_channel_write_blk64(fs->io, blk, 1, block_buf);
 146                 if (retval)
 147                         goto cleanup;
 148         }
 149
 150         /*
 151          * Link the symlink into the filesystem hierarchy
 152          */
 153         if (name) {
 154                 retval = ext2fs_lookup(fs, parent, name, strlen(name), 0,
 155                                        &scratch_ino);
 156                 if (!retval) {
 157                         retval = EXT2_ET_FILE_EXISTS;
 158                         goto cleanup;
 159                 }
 160                 if (retval != EXT2_ET_FILE_NOT_FOUND)
 161                         goto cleanup;
 162                 retval = ext2fs_link(fs, parent, name, ino, EXT2_FT_SYMLINK);
 163                 if (retval)
 164                         goto cleanup;
 165         }
 166
 167         /*
 168          * Update accounting....
 169          */
 170         if (!fastlink && !inlinelink)
 171                 ext2fs_block_alloc_stats2(fs, blk, +1);
 172         ext2fs_inode_alloc_stats2(fs, ino, +1, 0);
 173
 174 cleanup:
 175         if (block_buf)
 176                 ext2fs_free_mem(&block_buf);
 177         return retval;
 178 }