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, 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,
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  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,                   /* readpage */
  67         NULL,                   /* writepage */
  68         NULL,                   /* bmap */
  69         ext2_truncate,          /* truncate */
  70         ext2_permission,        /* permission */
  71         NULL                    /* smap */
  72 };
  73 
  74 int ext2_check_dir_entry (const 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         const 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 entry in directory #%lu: %s - "
  94                             "offset=%lu, inode=%lu, rec_len=%d, name_len=%d",
  95                             dir->i_ino, error_msg, offset, (unsigned long) de->inode,
  96                             de->rec_len, 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                          void * dirent, filldir_t filldir)
 102 {
 103         int error = 0;
 104         unsigned long offset, blk;
 105         int i, num, stored;
 106         struct buffer_head * bh, * tmp, * bha[16];
 107         struct ext2_dir_entry * de;
 108         struct super_block * sb;
 109         int err;
 110 
 111         if (!inode || !S_ISDIR(inode->i_mode))
 112                 return -EBADF;
 113         sb = inode->i_sb;
 114 
 115         stored = 0;
 116         bh = NULL;
 117         offset = filp->f_pos & (sb->s_blocksize - 1);
 118 
 119         while (!error && !stored && filp->f_pos < inode->i_size) {
 120                 blk = (filp->f_pos) >> EXT2_BLOCK_SIZE_BITS(sb);
 121                 bh = ext2_bread (inode, blk, 0, &err);
 122                 if (!bh) {
 123                         ext2_error (sb, "ext2_readdir",
 124                                     "directory #%lu contains a hole at offset %lu",
 125                                     inode->i_ino, (unsigned long)filp->f_pos);
 126                         filp->f_pos += sb->s_blocksize - offset;
 127                         continue;
 128                 }
 129 
 130                 /*
 131                  * Do the readahead
 132                  */
 133                 if (!offset) {
 134                         for (i = 16 >> (EXT2_BLOCK_SIZE_BITS(sb) - 9), num = 0;
 135                              i > 0; i--) {
 136                                 tmp = ext2_getblk (inode, ++blk, 0, &err);
 137                                 if (tmp && !buffer_uptodate(tmp) && !buffer_locked(tmp))
 138                                         bha[num++] = tmp;
 139                                 else
 140                                         brelse (tmp);
 141                         }
 142                         if (num) {
 143                                 ll_rw_block (READA, num, bha);
 144                                 for (i = 0; i < num; i++)
 145                                         brelse (bha[i]);
 146                         }
 147                 }
 148                 
 149 revalidate:
 150                 /* If the dir block has changed since the last call to
 151                  * readdir(2), then we might be pointing to an invalid
 152                  * dirent right now.  Scan from the start of the block
 153                  * to make sure. */
 154                 if (filp->f_version != inode->i_version) {
 155                         for (i = 0; i < sb->s_blocksize && i < offset; ) {
 156                                 de = (struct ext2_dir_entry *) 
 157                                         (bh->b_data + i);
 158                                 /* It's too expensive to do a full
 159                                  * dirent test each time round this
 160                                  * loop, but we do have to test at
 161                                  * least that it is non-zero.  A
 162                                  * failure will be detected in the
 163                                  * dirent test below. */
 164                                 if (de->rec_len < EXT2_DIR_REC_LEN(1))
 165                                         break;
 166                                 i += de->rec_len;
 167                         }
 168                         offset = i;
 169                         filp->f_pos = (filp->f_pos & ~(sb->s_blocksize - 1))
 170                                 | offset;
 171                         filp->f_version = inode->i_version;
 172                 }
 173                 
 174                 while (!error && filp->f_pos < inode->i_size 
 175                        && offset < sb->s_blocksize) {
 176                         de = (struct ext2_dir_entry *) (bh->b_data + offset);
 177                         if (!ext2_check_dir_entry ("ext2_readdir", inode, de,
 178                                                    bh, offset)) {
 179                                 /* On error, skip the f_pos to the
 180                                    next block. */
 181                                 filp->f_pos = (filp->f_pos & (sb->s_blocksize - 1))
 182                                               + sb->s_blocksize;
 183                                 brelse (bh);
 184                                 return stored;
 185                         }
 186                         offset += de->rec_len;
 187                         if (de->inode) {
 188                                 /* We might block in the next section
 189                                  * if the data destination is
 190                                  * currently swapped out.  So, use a
 191                                  * version stamp to detect whether or
 192                                  * not the directory has been modified
 193                                  * during the copy operation. */
 194                                 unsigned long version;
 195                                 dcache_add(inode, de->name, de->name_len, de->inode);
 196                                 version = inode->i_version;
 197                                 error = filldir(dirent, de->name, de->name_len, filp->f_pos, de->inode);
 198                                 if (error)
 199                                         break;
 200                                 if (version != inode->i_version)
 201                                         goto revalidate;
 202                                 stored ++;
 203                         }
 204                         filp->f_pos += de->rec_len;
 205                 }
 206                 offset = 0;
 207                 brelse (bh);
 208         }
 209         if (!IS_RDONLY(inode)) {
 210                 inode->i_atime = CURRENT_TIME;
 211                 inode->i_dirt = 1;
 212         }
 213         return 0;
 214 }

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