fs/efs/dir.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * dir.c
   4  *
   5  * Copyright (c) 1999 Al Smith
   6  */
   7
   8 #include <linux/buffer_head.h>
   9 #include "efs.h"
  10
  11 static int efs_readdir(struct file *, struct dir_context *);
  12
  13 const struct file_operations efs_dir_operations = {
  14         .llseek         = generic_file_llseek,
  15         .read           = generic_read_dir,
  16         .iterate_shared = efs_readdir,
  17 };
  18
  19 const struct inode_operations efs_dir_inode_operations = {
  20         .lookup         = efs_lookup,
  21 };
  22
  23 static int efs_readdir(struct file *file, struct dir_context *ctx)
  24 {
  25         struct inode *inode = file_inode(file);
  26         efs_block_t             block;
  27         int                     slot;
  28
  29         if (inode->i_size & (EFS_DIRBSIZE-1))
  30                 pr_warn("%s(): directory size not a multiple of EFS_DIRBSIZE\n",
  31                         __func__);
  32
  33         /* work out where this entry can be found */
  34         block = ctx->pos >> EFS_DIRBSIZE_BITS;
  35
  36         /* each block contains at most 256 slots */
  37         slot  = ctx->pos & 0xff;
  38
  39         /* look at all blocks */
  40         while (block < inode->i_blocks) {
  41                 struct efs_dir          *dirblock;
  42                 struct buffer_head *bh;
  43
  44                 /* read the dir block */
  45                 bh = sb_bread(inode->i_sb, efs_bmap(inode, block));
  46
  47                 if (!bh) {
  48                         pr_err("%s(): failed to read dir block %d\n",
  49                                __func__, block);
  50                         break;
  51                 }
  52
  53                 dirblock = (struct efs_dir *) bh->b_data;
  54
  55                 if (be16_to_cpu(dirblock->magic) != EFS_DIRBLK_MAGIC) {
  56                         pr_err("%s(): invalid directory block\n", __func__);
  57                         brelse(bh);
  58                         break;
  59                 }
  60
  61                 for (; slot < dirblock->slots; slot++) {
  62                         struct efs_dentry *dirslot;
  63                         efs_ino_t inodenum;
  64                         const char *nameptr;
  65                         int namelen;
  66
  67                         if (dirblock->space[slot] == 0)
  68                                 continue;
  69
  70                         dirslot  = (struct efs_dentry *) (((char *) bh->b_data) + EFS_SLOTAT(dirblock, slot));
  71
  72                         inodenum = be32_to_cpu(dirslot->inode);
  73                         namelen  = dirslot->namelen;
  74                         nameptr  = dirslot->name;
  75                         pr_debug("%s(): block %d slot %d/%d: inode %u, name \"%s\", namelen %u\n",
  76                                  __func__, block, slot, dirblock->slots-1,
  77                                  inodenum, nameptr, namelen);
  78                         if (!namelen)
  79                                 continue;
  80                         /* found the next entry */
  81                         ctx->pos = (block << EFS_DIRBSIZE_BITS) | slot;
  82
  83                         /* sanity check */
  84                         if (nameptr - (char *) dirblock + namelen > EFS_DIRBSIZE) {
  85                                 pr_warn("directory entry %d exceeds directory block\n",
  86                                         slot);
  87                                 continue;
  88                         }
  89
  90                         /* copy filename and data in dirslot */
  91                         if (!dir_emit(ctx, nameptr, namelen, inodenum, DT_UNKNOWN)) {
  92                                 brelse(bh);
  93                                 return 0;
  94                         }
  95                 }
  96                 brelse(bh);
  97
  98                 slot = 0;
  99                 block++;
 100         }
 101         ctx->pos = (block << EFS_DIRBSIZE_BITS) | slot;
 102         return 0;
 103 }