fs/ext3/dir.c

   1 /*
   2  *  linux/fs/ext3/dir.c
   3  *
   4  * Copyright (C) 1992, 1993, 1994, 1995
   5  * Remy Card (card@masi.ibp.fr)
   6  * Laboratoire MASI - Institut Blaise Pascal
   7  * Universite Pierre et Marie Curie (Paris VI)
   8  *
   9  *  from
  10  *
  11  *  linux/fs/minix/dir.c
  12  *
  13  *  Copyright (C) 1991, 1992  Linus Torvalds
  14  *
  15  *  ext3 directory handling functions
  16  *
  17  *  Big-endian to little-endian byte-swapping/bitmaps by
  18  *        David S. Miller (davem@caip.rutgers.edu), 1995
  19  */
  20
  21 #include <linux/fs.h>
  22 #include <linux/jbd.h>
  23 #include <linux/ext3_fs.h>
  24
  25 static unsigned char ext3_filetype_table[] = {
  26         DT_UNKNOWN, DT_REG, DT_DIR, DT_CHR, DT_BLK, DT_FIFO, DT_SOCK, DT_LNK
  27 };
  28
  29 static int ext3_readdir(struct file *, void *, filldir_t);
  30
  31 struct file_operations ext3_dir_operations = {
  32         read:           generic_read_dir,
  33         readdir:        ext3_readdir,           /* BKL held */
  34         ioctl:          ext3_ioctl,             /* BKL held */
  35         fsync:          ext3_sync_file,         /* BKL held */
  36 };
  37
  38 int ext3_check_dir_entry (const char * function, struct inode * dir,
  39                           struct ext3_dir_entry_2 * de,
  40                           struct buffer_head * bh,
  41                           unsigned long offset)
  42 {
  43         const char * error_msg = NULL;
  44         const int rlen = le16_to_cpu(de->rec_len);
  45
  46         if (rlen < EXT3_DIR_REC_LEN(1))
  47                 error_msg = "rec_len is smaller than minimal";
  48         else if (rlen % 4 != 0)
  49                 error_msg = "rec_len % 4 != 0";
  50         else if (rlen < EXT3_DIR_REC_LEN(de->name_len))
  51                 error_msg = "rec_len is too small for name_len";
  52         else if (((char *) de - bh->b_data) + rlen > dir->i_sb->s_blocksize)
  53                 error_msg = "directory entry across blocks";
  54         else if (le32_to_cpu(de->inode) >
  55                         le32_to_cpu(dir->i_sb->u.ext3_sb.s_es->s_inodes_count))
  56                 error_msg = "inode out of bounds";
  57
  58         if (error_msg != NULL)
  59                 ext3_error (dir->i_sb, function,
  60                         "bad entry in directory #%lu: %s - "
  61                         "offset=%lu, inode=%lu, rec_len=%d, name_len=%d",
  62                         dir->i_ino, error_msg, offset,
  63                         (unsigned long) le32_to_cpu(de->inode),
  64                         rlen, de->name_len);
  65         return error_msg == NULL ? 1 : 0;
  66 }
  67
  68 static int ext3_readdir(struct file * filp,
  69                          void * dirent, filldir_t filldir)
  70 {
  71         int error = 0;
  72         unsigned long offset, blk;
  73         int i, num, stored;
  74         struct buffer_head * bh, * tmp, * bha[16];
  75         struct ext3_dir_entry_2 * de;
  76         struct super_block * sb;
  77         int err;
  78         struct inode *inode = filp->f_dentry->d_inode;
  79
  80         sb = inode->i_sb;
  81
  82         stored = 0;
  83         bh = NULL;
  84         offset = filp->f_pos & (sb->s_blocksize - 1);
  85
  86         while (!error && !stored && filp->f_pos < inode->i_size) {
  87                 blk = (filp->f_pos) >> EXT3_BLOCK_SIZE_BITS(sb);
  88                 bh = ext3_bread (0, inode, blk, 0, &err);
  89                 if (!bh) {
  90                         ext3_error (sb, "ext3_readdir",
  91                                 "directory #%lu contains a hole at offset %lu",
  92                                 inode->i_ino, (unsigned long)filp->f_pos);
  93                         filp->f_pos += sb->s_blocksize - offset;
  94                         continue;
  95                 }
  96
  97                 /*
  98                  * Do the readahead
  99                  */
 100                 if (!offset) {
 101                         for (i = 16 >> (EXT3_BLOCK_SIZE_BITS(sb) - 9), num = 0;
 102                              i > 0; i--) {
 103                                 tmp = ext3_getblk (NULL, inode, ++blk, 0, &err);
 104                                 if (tmp && !buffer_uptodate(tmp) &&
 105                                                 !buffer_locked(tmp))
 106                                         bha[num++] = tmp;
 107                                 else
 108                                         brelse (tmp);
 109                         }
 110                         if (num) {
 111                                 ll_rw_block (READA, num, bha);
 112                                 for (i = 0; i < num; i++)
 113                                         brelse (bha[i]);
 114                         }
 115                 }
 116
 117 revalidate:
 118                 /* If the dir block has changed since the last call to
 119                  * readdir(2), then we might be pointing to an invalid
 120                  * dirent right now.  Scan from the start of the block
 121                  * to make sure. */
 122                 if (filp->f_version != inode->i_version) {
 123                         for (i = 0; i < sb->s_blocksize && i < offset; ) {
 124                                 de = (struct ext3_dir_entry_2 *)
 125                                         (bh->b_data + i);
 126                                 /* It's too expensive to do a full
 127                                  * dirent test each time round this
 128                                  * loop, but we do have to test at
 129                                  * least that it is non-zero.  A
 130                                  * failure will be detected in the
 131                                  * dirent test below. */
 132                                 if (le16_to_cpu(de->rec_len) <
 133                                                 EXT3_DIR_REC_LEN(1))
 134                                         break;
 135                                 i += le16_to_cpu(de->rec_len);
 136                         }
 137                         offset = i;
 138                         filp->f_pos = (filp->f_pos & ~(sb->s_blocksize - 1))
 139                                 | offset;
 140                         filp->f_version = inode->i_version;
 141                 }
 142
 143                 while (!error && filp->f_pos < inode->i_size
 144                        && offset < sb->s_blocksize) {
 145                         de = (struct ext3_dir_entry_2 *) (bh->b_data + offset);
 146                         if (!ext3_check_dir_entry ("ext3_readdir", inode, de,
 147                                                    bh, offset)) {
 148                                 /* On error, skip the f_pos to the
 149                                    next block. */
 150                                 filp->f_pos = (filp->f_pos |
 151                                                 (sb->s_blocksize - 1)) + 1;
 152                                 brelse (bh);
 153                                 return stored;
 154                         }
 155                         offset += le16_to_cpu(de->rec_len);
 156                         if (le32_to_cpu(de->inode)) {
 157                                 /* We might block in the next section
 158                                  * if the data destination is
 159                                  * currently swapped out.  So, use a
 160                                  * version stamp to detect whether or
 161                                  * not the directory has been modified
 162                                  * during the copy operation.
 163                                  */
 164                                 unsigned long version = filp->f_version;
 165                                 unsigned char d_type = DT_UNKNOWN;
 166
 167                                 if (EXT3_HAS_INCOMPAT_FEATURE(sb,
 168                                                 EXT3_FEATURE_INCOMPAT_FILETYPE)
 169                                                 && de->file_type < EXT3_FT_MAX)
 170                                         d_type =
 171                                           ext3_filetype_table[de->file_type];
 172                                 error = filldir(dirent, de->name,
 173                                                 de->name_len,
 174                                                 filp->f_pos,
 175                                                 le32_to_cpu(de->inode),
 176                                                 d_type);
 177                                 if (error)
 178                                         break;
 179                                 if (version != filp->f_version)
 180                                         goto revalidate;
 181                                 stored ++;
 182                         }
 183                         filp->f_pos += le16_to_cpu(de->rec_len);
 184                 }
 185                 offset = 0;
 186                 brelse (bh);
 187         }
 188         UPDATE_ATIME(inode);
 189         return 0;
 190 }