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Linux/fs/efs/dir.c

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  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 }
103 

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