LXR linux/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
  10static int efs_readdir(struct file *, struct dir_context *);
  11
  12const struct file_operations efs_dir_operations = {
  13        .llseek         = generic_file_llseek,
  14        .read           = generic_read_dir,
  15        .iterate        = efs_readdir,
  16};
  17
  18const struct inode_operations efs_dir_inode_operations = {
  19        .lookup         = efs_lookup,
  20};
  21
  22static 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}
 103
 104