fs/efs/dir.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  * dir.c
0004  *
0005  * Copyright (c) 1999 Al Smith
0006  */
0007
0008 #include <linux/buffer_head.h>
0009 #include "efs.h"
0010
0011 static int efs_readdir(struct file *, struct dir_context *);
0012
0013 const struct file_operations efs_dir_operations = {
0014     .llseek     = generic_file_llseek,
0015     .read       = generic_read_dir,
0016     .iterate_shared = efs_readdir,
0017 };
0018
0019 const struct inode_operations efs_dir_inode_operations = {
0020     .lookup     = efs_lookup,
0021 };
0022
0023 static int efs_readdir(struct file *file, struct dir_context *ctx)
0024 {
0025     struct inode *inode = file_inode(file);
0026     efs_block_t     block;
0027     int         slot;
0028
0029     if (inode->i_size & (EFS_DIRBSIZE-1))
0030         pr_warn("%s(): directory size not a multiple of EFS_DIRBSIZE\n",
0031             __func__);
0032
0033     /* work out where this entry can be found */
0034     block = ctx->pos >> EFS_DIRBSIZE_BITS;
0035
0036     /* each block contains at most 256 slots */
0037     slot  = ctx->pos & 0xff;
0038
0039     /* look at all blocks */
0040     while (block < inode->i_blocks) {
0041         struct efs_dir      *dirblock;
0042         struct buffer_head *bh;
0043
0044         /* read the dir block */
0045         bh = sb_bread(inode->i_sb, efs_bmap(inode, block));
0046
0047         if (!bh) {
0048             pr_err("%s(): failed to read dir block %d\n",
0049                    __func__, block);
0050             break;
0051         }
0052
0053         dirblock = (struct efs_dir *) bh->b_data;
0054
0055         if (be16_to_cpu(dirblock->magic) != EFS_DIRBLK_MAGIC) {
0056             pr_err("%s(): invalid directory block\n", __func__);
0057             brelse(bh);
0058             break;
0059         }
0060
0061         for (; slot < dirblock->slots; slot++) {
0062             struct efs_dentry *dirslot;
0063             efs_ino_t inodenum;
0064             const char *nameptr;
0065             int namelen;
0066
0067             if (dirblock->space[slot] == 0)
0068                 continue;
0069
0070             dirslot  = (struct efs_dentry *) (((char *) bh->b_data) + EFS_SLOTAT(dirblock, slot));
0071
0072             inodenum = be32_to_cpu(dirslot->inode);
0073             namelen  = dirslot->namelen;
0074             nameptr  = dirslot->name;
0075             pr_debug("%s(): block %d slot %d/%d: inode %u, name \"%s\", namelen %u\n",
0076                  __func__, block, slot, dirblock->slots-1,
0077                  inodenum, nameptr, namelen);
0078             if (!namelen)
0079                 continue;
0080             /* found the next entry */
0081             ctx->pos = (block << EFS_DIRBSIZE_BITS) | slot;
0082
0083             /* sanity check */
0084             if (nameptr - (char *) dirblock + namelen > EFS_DIRBSIZE) {
0085                 pr_warn("directory entry %d exceeds directory block\n",
0086                     slot);
0087                 continue;
0088             }
0089
0090             /* copy filename and data in dirslot */
0091             if (!dir_emit(ctx, nameptr, namelen, inodenum, DT_UNKNOWN)) {
0092                 brelse(bh);
0093                 return 0;
0094             }
0095         }
0096         brelse(bh);
0097
0098         slot = 0;
0099         block++;
0100     }
0101     ctx->pos = (block << EFS_DIRBSIZE_BITS) | slot;
0102     return 0;
0103 }