i386/linux/linux-2.3.21/fs/ext2/dir.c

   1 /*
   2  *  linux/fs/ext2/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  *  ext2 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 <asm/uaccess.h>
  22
  23 #include <linux/errno.h>
  24 #include <linux/fs.h>
  25 #include <linux/ext2_fs.h>
  26 #include <linux/sched.h>
  27 #include <linux/stat.h>
  28
  29 static ssize_t ext2_dir_read (struct file * filp, char * buf,
  30                               size_t count, loff_t *ppos)
  31 {
  32         return -EISDIR;
  33 }
  34
  35 static int ext2_readdir(struct file *, void *, filldir_t);
  36
  37 static struct file_operations ext2_dir_operations = {
  38         NULL,                   /* lseek - default */
  39         ext2_dir_read,          /* read */
  40         NULL,                   /* write - bad */
  41         ext2_readdir,           /* readdir */
  42         NULL,                   /* poll - default */
  43         ext2_ioctl,             /* ioctl */
  44         NULL,                   /* mmap */
  45         NULL,                   /* no special open code */
  46         NULL,                   /* flush */
  47         NULL,                   /* no special release code */
  48         ext2_sync_file,         /* fsync */
  49         NULL,                   /* fasync */
  50         NULL,                   /* check_media_change */
  51         NULL                    /* revalidate */
  52 };
  53
  54 /*
  55  * directories can handle most operations...
  56  */
  57 struct inode_operations ext2_dir_inode_operations = {
  58         &ext2_dir_operations,   /* default directory file-ops */
  59         ext2_create,            /* create */
  60         ext2_lookup,            /* lookup */
  61         ext2_link,              /* link */
  62         ext2_unlink,            /* unlink */
  63         ext2_symlink,           /* symlink */
  64         ext2_mkdir,             /* mkdir */
  65         ext2_rmdir,             /* rmdir */
  66         ext2_mknod,             /* mknod */
  67         ext2_rename,            /* rename */
  68         NULL,                   /* readlink */
  69         NULL,                   /* follow_link */
  70         NULL,                   /* get_block */
  71         NULL,                   /* readpage */
  72         NULL,                   /* writepage */
  73         NULL,                   /* flushpage */
  74         NULL,                   /* truncate */
  75         ext2_permission,        /* permission */
  76         NULL,                   /* smap */
  77         NULL                    /* revalidate */
  78 };
  79
  80 int ext2_check_dir_entry (const char * function, struct inode * dir,
  81                           struct ext2_dir_entry_2 * de,
  82                           struct buffer_head * bh,
  83                           unsigned long offset)
  84 {
  85         const char * error_msg = NULL;
  86
  87         if (le16_to_cpu(de->rec_len) < EXT2_DIR_REC_LEN(1))
  88                 error_msg = "rec_len is smaller than minimal";
  89         else if (le16_to_cpu(de->rec_len) % 4 != 0)
  90                 error_msg = "rec_len % 4 != 0";
  91         else if (le16_to_cpu(de->rec_len) < EXT2_DIR_REC_LEN(de->name_len))
  92                 error_msg = "rec_len is too small for name_len";
  93         else if (dir && ((char *) de - bh->b_data) + le16_to_cpu(de->rec_len) >
  94                  dir->i_sb->s_blocksize)
  95                 error_msg = "directory entry across blocks";
  96         else if (dir && le32_to_cpu(de->inode) > le32_to_cpu(dir->i_sb->u.ext2_sb.s_es->s_inodes_count))
  97                 error_msg = "inode out of bounds";
  98
  99         if (error_msg != NULL)
 100                 ext2_error (dir->i_sb, function, "bad entry in directory #%lu: %s - "
 101                             "offset=%lu, inode=%lu, rec_len=%d, name_len=%d",
 102                             dir->i_ino, error_msg, offset,
 103                             (unsigned long) le32_to_cpu(de->inode),
 104                             le16_to_cpu(de->rec_len), de->name_len);
 105         return error_msg == NULL ? 1 : 0;
 106 }
 107
 108 static int ext2_readdir(struct file * filp,
 109                          void * dirent, filldir_t filldir)
 110 {
 111         int error = 0;
 112         unsigned long offset, blk;
 113         int i, num, stored;
 114         struct buffer_head * bh, * tmp, * bha[16];
 115         struct ext2_dir_entry_2 * de;
 116         struct super_block * sb;
 117         int err;
 118         struct inode *inode = filp->f_dentry->d_inode;
 119
 120         sb = inode->i_sb;
 121
 122         stored = 0;
 123         bh = NULL;
 124         offset = filp->f_pos & (sb->s_blocksize - 1);
 125
 126         while (!error && !stored && filp->f_pos < inode->i_size) {
 127                 blk = (filp->f_pos) >> EXT2_BLOCK_SIZE_BITS(sb);
 128                 bh = ext2_bread (inode, blk, 0, &err);
 129                 if (!bh) {
 130                         ext2_error (sb, "ext2_readdir",
 131                                     "directory #%lu contains a hole at offset %lu",
 132                                     inode->i_ino, (unsigned long)filp->f_pos);
 133                         filp->f_pos += sb->s_blocksize - offset;
 134                         continue;
 135                 }
 136
 137                 /*
 138                  * Do the readahead
 139                  */
 140                 if (!offset) {
 141                         for (i = 16 >> (EXT2_BLOCK_SIZE_BITS(sb) - 9), num = 0;
 142                              i > 0; i--) {
 143                                 tmp = ext2_getblk (inode, ++blk, 0, &err);
 144                                 if (tmp && !buffer_uptodate(tmp) && !buffer_locked(tmp))
 145                                         bha[num++] = tmp;
 146                                 else
 147                                         brelse (tmp);
 148                         }
 149                         if (num) {
 150                                 ll_rw_block (READA, num, bha);
 151                                 for (i = 0; i < num; i++)
 152                                         brelse (bha[i]);
 153                         }
 154                 }
 155
 156 revalidate:
 157                 /* If the dir block has changed since the last call to
 158                  * readdir(2), then we might be pointing to an invalid
 159                  * dirent right now.  Scan from the start of the block
 160                  * to make sure. */
 161                 if (filp->f_version != inode->i_version) {
 162                         for (i = 0; i < sb->s_blocksize && i < offset; ) {
 163                                 de = (struct ext2_dir_entry_2 *)
 164                                         (bh->b_data + i);
 165                                 /* It's too expensive to do a full
 166                                  * dirent test each time round this
 167                                  * loop, but we do have to test at
 168                                  * least that it is non-zero.  A
 169                                  * failure will be detected in the
 170                                  * dirent test below. */
 171                                 if (le16_to_cpu(de->rec_len) < EXT2_DIR_REC_LEN(1))
 172                                         break;
 173                                 i += le16_to_cpu(de->rec_len);
 174                         }
 175                         offset = i;
 176                         filp->f_pos = (filp->f_pos & ~(sb->s_blocksize - 1))
 177                                 | offset;
 178                         filp->f_version = inode->i_version;
 179                 }
 180
 181                 while (!error && filp->f_pos < inode->i_size
 182                        && offset < sb->s_blocksize) {
 183                         de = (struct ext2_dir_entry_2 *) (bh->b_data + offset);
 184                         if (!ext2_check_dir_entry ("ext2_readdir", inode, de,
 185                                                    bh, offset)) {
 186                                 /* On error, skip the f_pos to the
 187                                    next block. */
 188                                 filp->f_pos = (filp->f_pos & (sb->s_blocksize - 1))
 189                                               + sb->s_blocksize;
 190                                 brelse (bh);
 191                                 return stored;
 192                         }
 193                         offset += le16_to_cpu(de->rec_len);
 194                         if (le32_to_cpu(de->inode)) {
 195                                 /* We might block in the next section
 196                                  * if the data destination is
 197                                  * currently swapped out.  So, use a
 198                                  * version stamp to detect whether or
 199                                  * not the directory has been modified
 200                                  * during the copy operation.
 201                                  */
 202                                 unsigned long version = inode->i_version;
 203
 204                                 error = filldir(dirent, de->name,
 205                                                 de->name_len,
 206                                                 filp->f_pos, le32_to_cpu(de->inode));
 207                                 if (error)
 208                                         break;
 209                                 if (version != inode->i_version)
 210                                         goto revalidate;
 211                                 stored ++;
 212                         }
 213                         filp->f_pos += le16_to_cpu(de->rec_len);
 214                 }
 215                 offset = 0;
 216                 brelse (bh);
 217         }
 218         UPDATE_ATIME(inode);
 219         return 0;
 220 }