fs/ext2/dir.c

/* */
This source file includes following definitions.
ext2_dir_read
ext2_check_dir_entry
ext2_readdir
   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 
  18 #include <asm/segment.h>
  19 
  20 #include <linux/errno.h>
  21 #include <linux/fs.h>
  22 #include <linux/ext2_fs.h>
  23 #include <linux/sched.h>
  24 #include <linux/stat.h>
  25 
  26 static int ext2_dir_read (struct inode * inode, struct file * filp,
     /*  */
  27                             char * buf, int count)
  28 {
  29         return -EISDIR;
  30 }
  31 
  32 static int ext2_readdir (struct inode *, struct file *, void *, filldir_t);
  33 
  34 static struct file_operations ext2_dir_operations = {
  35         NULL,                   /* lseek - default */
  36         ext2_dir_read,          /* read */
  37         NULL,                   /* write - bad */
  38         ext2_readdir,           /* readdir */
  39         NULL,                   /* select - default */
  40         ext2_ioctl,             /* ioctl */
  41         NULL,                   /* mmap */
  42         NULL,                   /* no special open code */
  43         NULL,                   /* no special release code */
  44         file_fsync,             /* fsync */
  45         NULL,                   /* fasync */
  46         NULL,                   /* check_media_change */
  47         NULL                    /* revalidate */
  48 };
  49 
  50 /*
  51  * directories can handle most operations...
  52  */
  53 struct inode_operations ext2_dir_inode_operations = {
  54         &ext2_dir_operations,   /* default directory file-ops */
  55         ext2_create,            /* create */
  56         ext2_lookup,            /* lookup */
  57         ext2_link,              /* link */
  58         ext2_unlink,            /* unlink */
  59         ext2_symlink,           /* symlink */
  60         ext2_mkdir,             /* mkdir */
  61         ext2_rmdir,             /* rmdir */
  62         ext2_mknod,             /* mknod */
  63         ext2_rename,            /* rename */
  64         NULL,                   /* readlink */
  65         NULL,                   /* follow_link */
  66         NULL,                   /* bmap */
  67         ext2_truncate,          /* truncate */
  68         ext2_permission,        /* permission */
  69         NULL                    /* smap */
  70 };
  71 
  72 int ext2_check_dir_entry (const char * function, struct inode * dir,
     /*  */
  73                           struct ext2_dir_entry * de, struct buffer_head * bh,
  74                           unsigned long offset)
  75 {
  76         const char * error_msg = NULL;
  77 
  78         if (de->rec_len < EXT2_DIR_REC_LEN(1))
  79                 error_msg = "rec_len is smaller than minimal";
  80         else if (de->rec_len % 4 != 0)
  81                 error_msg = "rec_len % 4 != 0";
  82         else if (de->rec_len < EXT2_DIR_REC_LEN(de->name_len))
  83                 error_msg = "rec_len is too small for name_len";
  84         else if (dir && ((char *) de - bh->b_data) + de->rec_len >
  85                  dir->i_sb->s_blocksize)
  86                 error_msg = "directory entry across blocks";
  87         else if (dir && de->inode > dir->i_sb->u.ext2_sb.s_es->s_inodes_count)
  88                 error_msg = "inode out of bounds";
  89 
  90         if (error_msg != NULL)
  91                 ext2_error (dir->i_sb, function, "bad entry in directory #%lu: %s - "
  92                             "offset=%lu, inode=%lu, rec_len=%d, name_len=%d",
  93                             dir->i_ino, error_msg, offset, (unsigned long) de->inode,
  94                             de->rec_len, de->name_len);
  95         return error_msg == NULL ? 1 : 0;
  96 }
  97 
  98 static int ext2_readdir (struct inode * inode, struct file * filp,
     /*  */
  99                          void * dirent, filldir_t filldir)
 100 {
 101         int error = 0;
 102         unsigned long offset, blk;
 103         int i, num, stored;
 104         struct buffer_head * bh, * tmp, * bha[16];
 105         struct ext2_dir_entry * de;
 106         struct super_block * sb;
 107         int err, version;
 108 
 109         if (!inode || !S_ISDIR(inode->i_mode))
 110                 return -EBADF;
 111         sb = inode->i_sb;
 112 
 113         stored = 0;
 114         bh = NULL;
 115         offset = filp->f_pos & (sb->s_blocksize - 1);
 116 
 117         while (!error && !stored && filp->f_pos < inode->i_size) {
 118                 blk = (filp->f_pos) >> EXT2_BLOCK_SIZE_BITS(sb);
 119                 bh = ext2_bread (inode, blk, 0, &err);
 120                 if (!bh) {
 121                         ext2_error (sb, "ext2_readdir",
 122                                     "directory #%lu contains a hole at offset %lu",
 123                                     inode->i_ino, (unsigned long)filp->f_pos);
 124                         filp->f_pos += sb->s_blocksize - offset;
 125                         continue;
 126                 }
 127 
 128                 /*
 129                  * Do the readahead
 130                  */
 131                 if (!offset) {
 132                         for (i = 16 >> (EXT2_BLOCK_SIZE_BITS(sb) - 9), num = 0;
 133                              i > 0; i--) {
 134                                 tmp = ext2_getblk (inode, ++blk, 0, &err);
 135                                 if (tmp && !tmp->b_uptodate && !tmp->b_lock)
 136                                         bha[num++] = tmp;
 137                                 else
 138                                         brelse (tmp);
 139                         }
 140                         if (num) {
 141                                 ll_rw_block (READA, num, bha);
 142                                 for (i = 0; i < num; i++)
 143                                         brelse (bha[i]);
 144                         }
 145                 }
 146                 
 147 revalidate:
 148                 /* If the dir block has changed since the last call to
 149                  * readdir(2), then we might be pointing to an invalid
 150                  * dirent right now.  Scan from the start of the block
 151                  * to make sure. */
 152                 if (filp->f_version != inode->i_version) {
 153                         for (i = 0; i < sb->s_blocksize && i < offset; ) {
 154                                 de = (struct ext2_dir_entry *) 
 155                                         (bh->b_data + i);
 156                                 /* It's too expensive to do a full
 157                                  * dirent test each time round this
 158                                  * loop, but we do have to test at
 159                                  * least that it is non-zero.  A
 160                                  * failure will be detected in the
 161                                  * dirent test below. */
 162                                 if (de->rec_len < EXT2_DIR_REC_LEN(1))
 163                                         break;
 164                                 i += de->rec_len;
 165                         }
 166                         offset = i;
 167                         filp->f_pos = (filp->f_pos & ~(sb->s_blocksize - 1))
 168                                 | offset;
 169                         filp->f_version = inode->i_version;
 170                 }
 171                 
 172                 while (!error && filp->f_pos < inode->i_size 
 173                        && offset < sb->s_blocksize) {
 174                         de = (struct ext2_dir_entry *) (bh->b_data + offset);
 175                         if (!ext2_check_dir_entry ("ext2_readdir", inode, de,
 176                                                    bh, offset)) {
 177                                 /* On error, skip the f_pos to the
 178                                    next block. */
 179                                 filp->f_pos = (filp->f_pos & (sb->s_blocksize - 1))
 180                                               + sb->s_blocksize;
 181                                 brelse (bh);
 182                                 return stored;
 183                         }
 184                         offset += de->rec_len;
 185                         if (de->inode) {
 186                                 /* We might block in the next section
 187                                  * if the data destination is
 188                                  * currently swapped out.  So, use a
 189                                  * version stamp to detect whether or
 190                                  * not the directory has been modified
 191                                  * during the copy operation. */
 192                                 version = inode->i_version;
 193                                 error = filldir(dirent, de->name, de->name_len, filp->f_pos, de->inode);
 194                                 if (error)
 195                                         break;
 196                                 if (version != inode->i_version)
 197                                         goto revalidate;
 198                                 stored ++;
 199                         }
 200                         filp->f_pos += de->rec_len;
 201                 }
 202                 offset = 0;
 203                 brelse (bh);
 204         }
 205         if (!IS_RDONLY(inode)) {
 206                 inode->i_atime = CURRENT_TIME;
 207                 inode->i_dirt = 1;
 208         }
 209         return 0;
 210 }
/* */
root/fs/ext2/dir.c

DEFINITIONS
