root/fs/ext2/dir.c

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DEFINITIONS

This source file includes following definitions.
  1. ext2_dir_read
  2. ext2_check_dir_entry
  3. ext2_readdir

   1 /*
   2  *  linux/fs/ext2/dir.c
   3  *
   4  *  Copyright (C) 1992, 1993, 1994  Remy Card (card@masi.ibp.fr)
   5  *                                  Laboratoire MASI - Institut Blaise Pascal
   6  *                                  Universite Pierre et Marie Curie (Paris VI)
   7  *
   8  *  from
   9  *
  10  *  linux/fs/minix/dir.c
  11  *
  12  *  Copyright (C) 1991, 1992  Linus Torvalds
  13  *
  14  *  ext2 directory handling functions
  15  */
  16 
  17 #include <asm/segment.h>
  18 
  19 #include <linux/errno.h>
  20 #include <linux/fs.h>
  21 #include <linux/ext2_fs.h>
  22 #include <linux/sched.h>
  23 #include <linux/stat.h>
  24 
  25 #define NAME_OFFSET(de) ((int) ((de)->d_name - (char *) (de)))
  26 #define ROUND_UP(x) (((x)+3) & ~3)
  27 
  28 static int ext2_dir_read (struct inode * inode, struct file * filp,
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  29                             char * buf, int count)
  30 {
  31         return -EISDIR;
  32 }
  33 
  34 static int ext2_readdir (struct inode *, struct file *, struct dirent *, int);
  35 
  36 static struct file_operations ext2_dir_operations = {
  37         NULL,                   /* lseek - default */
  38         ext2_dir_read,          /* read */
  39         NULL,                   /* write - bad */
  40         ext2_readdir,           /* readdir */
  41         NULL,                   /* select - default */
  42         ext2_ioctl,             /* ioctl */
  43         NULL,                   /* mmap */
  44         NULL,                   /* no special open code */
  45         NULL,                   /* no special release code */
  46         file_fsync,             /* fsync */
  47         NULL,                   /* fasync */
  48         NULL,                   /* check_media_change */
  49         NULL                    /* revalidate */
  50 };
  51 
  52 /*
  53  * directories can handle most operations...
  54  */
  55 struct inode_operations ext2_dir_inode_operations = {
  56         &ext2_dir_operations,   /* default directory file-ops */
  57         ext2_create,            /* create */
  58         ext2_lookup,            /* lookup */
  59         ext2_link,              /* link */
  60         ext2_unlink,            /* unlink */
  61         ext2_symlink,           /* symlink */
  62         ext2_mkdir,             /* mkdir */
  63         ext2_rmdir,             /* rmdir */
  64         ext2_mknod,             /* mknod */
  65         ext2_rename,            /* rename */
  66         NULL,                   /* readlink */
  67         NULL,                   /* follow_link */
  68         NULL,                   /* bmap */
  69         ext2_truncate,          /* truncate */
  70         ext2_permission,        /* permission */
  71         NULL                    /* smap */
  72 };
  73 
  74 int ext2_check_dir_entry (char * function, struct inode * dir,
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  75                           struct ext2_dir_entry * de, struct buffer_head * bh,
  76                           unsigned long offset)
  77 {
  78         char * error_msg = NULL;
  79 
  80         if (de->rec_len < EXT2_DIR_REC_LEN(1))
  81                 error_msg = "rec_len is smaller than minimal";
  82         else if (de->rec_len % 4 != 0)
  83                 error_msg = "rec_len % 4 != 0";
  84         else if (de->rec_len < EXT2_DIR_REC_LEN(de->name_len))
  85                 error_msg = "rec_len is too small for name_len";
  86         else if (dir && ((char *) de - bh->b_data) + de->rec_len >
  87                  dir->i_sb->s_blocksize)
  88                 error_msg = "directory entry across blocks";
  89         else if (dir && de->inode > dir->i_sb->u.ext2_sb.s_es->s_inodes_count)
  90                 error_msg = "inode out of bounds";
  91 
  92         if (error_msg != NULL)
  93                 ext2_error (dir->i_sb, function, "bad directory entry: %s\n"
  94                             "offset=%lu, inode=%lu, rec_len=%d, name_len=%d",
  95                             error_msg, offset, (unsigned long) de->inode, de->rec_len,
  96                             de->name_len);
  97         return error_msg == NULL ? 1 : 0;
  98 }
  99 
 100 static int ext2_readdir (struct inode * inode, struct file * filp,
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 101                          struct dirent * dirent, int count)
 102 {
 103         unsigned long offset, blk;
 104         int i, num, stored, dlen;
 105         struct buffer_head * bh, * tmp, * bha[16];
 106         struct ext2_dir_entry * de;
 107         struct super_block * sb;
 108         int err, version;
 109 
 110         if (!inode || !S_ISDIR(inode->i_mode))
 111                 return -EBADF;
 112         sb = inode->i_sb;
 113 
 114         stored = 0;
 115         bh = NULL;
 116         offset = filp->f_pos & (sb->s_blocksize - 1);
 117 
 118         while (count > 0 && !stored && filp->f_pos < inode->i_size) {
 119                 blk = (filp->f_pos) >> EXT2_BLOCK_SIZE_BITS(sb);
 120                 bh = ext2_bread (inode, blk, 0, &err);
 121                 if (!bh) {
 122                         filp->f_pos += sb->s_blocksize - offset;
 123                         continue;
 124                 }
 125 
 126                 /*
 127                  * Do the readahead
 128                  */
 129                 if (!offset) {
 130                         for (i = 16 >> (EXT2_BLOCK_SIZE_BITS(sb) - 9), num = 0;
 131                              i > 0; i--) {
 132                                 tmp = ext2_getblk (inode, ++blk, 0, &err);
 133                                 if (tmp && !tmp->b_uptodate && !tmp->b_lock)
 134                                         bha[num++] = tmp;
 135                                 else
 136                                         brelse (tmp);
 137                         }
 138                         if (num) {
 139                                 ll_rw_block (READA, num, bha);
 140                                 for (i = 0; i < num; i++)
 141                                         brelse (bha[i]);
 142                         }
 143                 }
 144                 
 145 revalidate:
 146                 /* If the dir block has changed since the last call to
 147                  * readdir(2), then we might be pointing to an invalid
 148                  * dirent right now.  Scan from the start of the block
 149                  * to make sure. */
 150                 if (filp->f_version != inode->i_version) {
 151                         for (i = 0; i < sb->s_blocksize && i < offset; ) {
 152                                 de = (struct ext2_dir_entry *) 
 153                                         (bh->b_data + i);
 154                                 /* It's too expensive to do a full
 155                                  * dirent test each time round this
 156                                  * loop, but we do have to test at
 157                                  * least that it is non-zero.  A
 158                                  * failure will be detected in the
 159                                  * dirent test below. */
 160                                 if (de->rec_len < EXT2_DIR_REC_LEN(1))
 161                                         break;
 162                                 i += de->rec_len;
 163                         }
 164                         offset = i;
 165                         filp->f_pos = (filp->f_pos & ~(sb->s_blocksize - 1))
 166                                 | offset;
 167                         filp->f_version = inode->i_version;
 168                 }
 169                 
 170                 while (count > 0 && filp->f_pos < inode->i_size 
 171                        && offset < sb->s_blocksize) {
 172                         de = (struct ext2_dir_entry *) (bh->b_data + offset);
 173                         if (!ext2_check_dir_entry ("ext2_readdir", inode, de,
 174                                                    bh, offset)) {
 175                                 /* On error, skip the f_pos to the
 176                                    next block. */
 177                                 filp->f_pos = (filp->f_pos & (sb->s_blocksize - 1))
 178                                               + sb->s_blocksize;
 179                                 brelse (bh);
 180                                 return stored;
 181                         }
 182                         if (de->inode) {
 183                                 dlen = ROUND_UP(NAME_OFFSET(dirent) 
 184                                                 + de->name_len + 1);
 185                                 /* Old libc libraries always use a
 186                                    count of 1. */
 187                                 if (count == 1 && !stored)
 188                                         count = dlen;
 189                                 if (count < dlen) {
 190                                         count = 0;
 191                                         break;
 192                                 }
 193 
 194                                 /* We might block in the next section
 195                                  * if the data destination is
 196                                  * currently swapped out.  So, use a
 197                                  * version stamp to detect whether or
 198                                  * not the directory has been modified
 199                                  * during the copy operation. */
 200                                 version = inode->i_version;
 201                                 i = de->name_len;
 202                                 memcpy_tofs (dirent->d_name, de->name, i);
 203                                 put_fs_long (de->inode, &dirent->d_ino);
 204                                 put_fs_byte (0, dirent->d_name + i);
 205                                 put_fs_word (i, &dirent->d_reclen);
 206                                 put_fs_long (dlen, &dirent->d_off);
 207                                 if (version != inode->i_version)
 208                                         goto revalidate;
 209                                 dcache_add(inode, de->name, de->name_len,
 210                                                  de->inode);
 211 
 212                                 stored += dlen;
 213                                 count -= dlen;
 214                                 ((char *) dirent) += dlen;
 215                         }
 216                         offset += de->rec_len;
 217                         filp->f_pos += de->rec_len;
 218                 }
 219                 offset = 0;
 220                 brelse (bh);
 221         }
 222         if (!IS_RDONLY(inode)) {
 223                 inode->i_atime = CURRENT_TIME;
 224                 inode->i_dirt = 1;
 225         }
 226         return stored;
 227 }

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