fs/efs/dir.c

   1 /*
   2  * dir.c
   3  *
   4  * Copyright (c) 1999 Al Smith
   5  */
   6
   7 #include <linux/buffer_head.h>
   8 #include "efs.h"
   9
  10 static int efs_readdir(struct file *, struct dir_context *);
  11
  12 const struct file_operations efs_dir_operations = {
  13         .llseek         = generic_file_llseek,
  14         .read           = generic_read_dir,
  15         .iterate_shared = efs_readdir,
  16 };
  17
  18 const struct inode_operations efs_dir_inode_operations = {
  19         .lookup         = efs_lookup,
  20 };
  21
  22 static int efs_readdir(struct file *file, struct dir_context *ctx)
  23 {
  24         struct inode *inode = file_inode(file);
  25         efs_block_t             block;
  26         int                     slot;
  27
  28         if (inode->i_size & (EFS_DIRBSIZE-1))
  29                 pr_warn("%s(): directory size not a multiple of EFS_DIRBSIZE\n",
  30                         __func__);
  31
  32         /* work out where this entry can be found */
  33         block = ctx->pos >> EFS_DIRBSIZE_BITS;
  34
  35         /* each block contains at most 256 slots */
  36         slot  = ctx->pos & 0xff;
  37
  38         /* look at all blocks */
  39         while (block < inode->i_blocks) {
  40                 struct efs_dir          *dirblock;
  41                 struct buffer_head *bh;
  42
  43                 /* read the dir block */
  44                 bh = sb_bread(inode->i_sb, efs_bmap(inode, block));
  45
  46                 if (!bh) {
  47                         pr_err("%s(): failed to read dir block %d\n",
  48                                __func__, block);
  49                         break;
  50                 }
  51
  52                 dirblock = (struct efs_dir *) bh->b_data;
  53
  54                 if (be16_to_cpu(dirblock->magic) != EFS_DIRBLK_MAGIC) {
  55                         pr_err("%s(): invalid directory block\n", __func__);
  56                         brelse(bh);
  57                         break;
  58                 }
  59
  60                 for (; slot < dirblock->slots; slot++) {
  61                         struct efs_dentry *dirslot;
  62                         efs_ino_t inodenum;
  63                         const char *nameptr;
  64                         int namelen;
  65
  66                         if (dirblock->space[slot] == 0)
  67                                 continue;
  68
  69                         dirslot  = (struct efs_dentry *) (((char *) bh->b_data) + EFS_SLOTAT(dirblock, slot));
  70
  71                         inodenum = be32_to_cpu(dirslot->inode);
  72                         namelen  = dirslot->namelen;
  73                         nameptr  = dirslot->name;
  74                         pr_debug("%s(): block %d slot %d/%d: inode %u, name \"%s\", namelen %u\n",
  75                                  __func__, block, slot, dirblock->slots-1,
  76                                  inodenum, nameptr, namelen);
  77                         if (!namelen)
  78                                 continue;
  79                         /* found the next entry */
  80                         ctx->pos = (block << EFS_DIRBSIZE_BITS) | slot;
  81
  82                         /* sanity check */
  83                         if (nameptr - (char *) dirblock + namelen > EFS_DIRBSIZE) {
  84                                 pr_warn("directory entry %d exceeds directory block\n",
  85                                         slot);
  86                                 continue;
  87                         }
  88
  89                         /* copy filename and data in dirslot */
  90                         if (!dir_emit(ctx, nameptr, namelen, inodenum, DT_UNKNOWN)) {
  91                                 brelse(bh);
  92                                 return 0;
  93                         }
  94                 }
  95                 brelse(bh);
  96
  97                 slot = 0;
  98                 block++;
  99         }
 100         ctx->pos = (block << EFS_DIRBSIZE_BITS) | slot;
 101         return 0;
 102 }